Cheers Bill - that was it.
I deleted a couple of old snaps and a mirror and it gave me enough space to expand.
I think I need to do a 'reserve 101' course . . .
Raj.
On Dec 3, 2007 3:02 PM, Neil Stichbury Neil.Stichbury@gen-i.co.nz wrote:
How do you define 'free space'? Do you have fractional_reserve, snap reserve set?
-----Original Message----- From: owner-toasters@mathworks.com [mailto:owner-toasters@mathworks.com] On Behalf Of Raj Patel Sent: Monday, 3 December 2007 1:16 p.m. To: toasters@mathworks.com Subject: Can't expand SnapDrive for Windows drive
Just trying to expand a 20Gb lun used for SQL 2005 logs - Its contained within a 400Gb volume (I've allocated 140 for the database, 20 for logs and 10 for temp db). The vol is sized at well over twice the space requirements to allow for snaps. I just want to expand the log lun to 40Gb.
Server is w2k3 sp1 SnapDrive 4.2.1 and OnTap 7.0.5 on a fas 270. SnapManager SQL is installed for SQL 2005.
Overall SAN free space is about 80Gb.
From within Windows the error SnapDrive gives is 'Unable to Expand Disk / Error there is not enough free space'
Anything obvious I'm missing ?
Thanks in advance,
Raj.
This communication, including any attachments, is confidential. If you are not the intended recipient, you should not read it - please contact me immediately, destroy it, and do not copy or use any part of this communication or disclose anything about it. Thank you. Please note that this communication does not designate an information system for the purposes of the Electronic Transactions Act 2002.
Hi Raj,
It's easier than it seems! :-) Anyway I suggest to read the TR 3431 and TR 3541 on "best practice" on SMSQL and SME where the concepts of space reservation, lun thin provisioning and so on are very well descrive.
I take this opportunity to ask here:
The LUN reserved for SnapInfo in SMSQL environments need to be half in size of the containing volume? I don't think so for it has to contain only logs and streamed images of the system db (model, master...). Opinions?
-----Messaggio originale----- Da: owner-toasters@mathworks.com [mailto:owner-toasters@mathworks.com] Per conto di Raj Patel Inviato: lunedì 3 dicembre 2007 3.24 A: toasters@mathworks.com Oggetto: Re: Can't expand SnapDrive for Windows drive
Cheers Bill - that was it.
I deleted a couple of old snaps and a mirror and it gave me enough space to expand.
I think I need to do a 'reserve 101' course . . .
Raj.
On Dec 3, 2007 3:02 PM, Neil Stichbury Neil.Stichbury@gen-i.co.nz wrote:
How do you define 'free space'? Do you have fractional_reserve, snap reserve set?
-----Original Message----- From: owner-toasters@mathworks.com [mailto:owner-toasters@mathworks.com] On Behalf Of Raj Patel Sent: Monday, 3 December 2007 1:16 p.m. To: toasters@mathworks.com Subject: Can't expand SnapDrive for Windows drive
Just trying to expand a 20Gb lun used for SQL 2005 logs - Its contained within a 400Gb volume (I've allocated 140 for the database, 20 for logs and 10 for temp db). The vol is sized at well over twice the space requirements to allow for snaps. I just want to expand the log lun to 40Gb.
Server is w2k3 sp1 SnapDrive 4.2.1 and OnTap 7.0.5 on a fas 270. SnapManager SQL is installed for SQL 2005.
Overall SAN free space is about 80Gb.
From within Windows the error SnapDrive gives is 'Unable to Expand Disk / Error there is not enough free space'
Anything obvious I'm missing ?
Thanks in advance,
Raj.
This communication, including any attachments, is confidential. If you are not the intended recipient, you should not read it - please contact me immediately, destroy it, and do not copy or use any part of this communication or disclose anything about it. Thank you. Please note that this communication does not designate an information system for the purposes of the Electronic Transactions Act 2002.
The default is to have a volume at least twice the size of a LUN to accomodate at least one full snapshot. If you don't need snapshots then you don't need space reservation. Not sure about SQL environments, but in Oracle environments we've seen the need to have larger volume:LUN ratios because log volumes actually change more blocks (proportionally speaking) because you are creating and deleting more files. The data files typically add blocks but don't delete them, depending of course on the database activity. We add data to our Oracle databases, but seldom delete anything.
-----Original Message----- From: owner-toasters@mathworks.com [mailto:owner-toasters@mathworks.com] On Behalf Of Milazzo Giacomo Sent: Monday, December 03, 2007 2:56 AM To: Raj Patel Cc: toasters@mathworks.com Subject: R: Can't expand SnapDrive for Windows drive
Hi Raj,
It's easier than it seems! :-) Anyway I suggest to read the TR 3431 and TR 3541 on "best practice" on SMSQL and SME where the concepts of space reservation, lun thin provisioning and so on are very well descrive.
I take this opportunity to ask here:
The LUN reserved for SnapInfo in SMSQL environments need to be half in size of the containing volume? I don't think so for it has to contain only logs and streamed images of the system db (model, master...). Opinions?
-----Messaggio originale----- Da: owner-toasters@mathworks.com [mailto:owner-toasters@mathworks.com] Per conto di Raj Patel Inviato: lunedì 3 dicembre 2007 3.24 A: toasters@mathworks.com Oggetto: Re: Can't expand SnapDrive for Windows drive
Cheers Bill - that was it.
I deleted a couple of old snaps and a mirror and it gave me enough space to expand.
I think I need to do a 'reserve 101' course . . .
Raj.
On Dec 3, 2007 3:02 PM, Neil Stichbury Neil.Stichbury@gen-i.co.nz wrote:
How do you define 'free space'? Do you have fractional_reserve, snap reserve set?
-----Original Message----- From: owner-toasters@mathworks.com [mailto:owner-toasters@mathworks.com] On Behalf Of Raj Patel Sent: Monday, 3 December 2007 1:16 p.m. To: toasters@mathworks.com Subject: Can't expand SnapDrive for Windows drive
Just trying to expand a 20Gb lun used for SQL 2005 logs - Its contained within a 400Gb volume (I've allocated 140 for the database, 20 for logs and 10 for temp db). The vol is sized at well over twice the space requirements to allow for snaps. I just want to expand the log lun to 40Gb.
Server is w2k3 sp1 SnapDrive 4.2.1 and OnTap 7.0.5 on a fas 270. SnapManager SQL is installed for SQL 2005.
Overall SAN free space is about 80Gb.
From within Windows the error SnapDrive gives is 'Unable to Expand Disk / Error there is not enough free space'
Anything obvious I'm missing ?
Thanks in advance,
Raj.
This communication, including any attachments, is confidential. If you are not the intended recipient, you should not read it - please contact me immediately, destroy it, and do not copy or use any part of this communication or disclose anything about it. Thank you. Please note that this communication does not designate an information system for the purposes of the Electronic Transactions Act 2002.
The default is to have a volume at least twice the size of a LUN to
accomodate at least one full snapshot.
I have heard the new versions of DataOntap and SnapDrive allow for a lower ratio - I'm guessing you can't retrospectively upgrade and reduce the space allocation on existing volumes ?
Or have I misheard the capabilities of the new versions ?
Cheers, Raj.
You can lower it. vol options <volname> fractional_reserve xx
-----Original Message----- From: Raj Patel [mailto:phigmov@gmail.com] Sent: Monday, December 03, 2007 1:02 PM To: Holland, William L Cc: Milazzo Giacomo; toasters@mathworks.com Subject: Re: Can't expand SnapDrive for Windows drive
The default is to have a volume at least twice the size of a LUN to
accomodate at least one full snapshot.
I have heard the new versions of DataOntap and SnapDrive allow for a lower ratio - I'm guessing you can't retrospectively upgrade and reduce the space allocation on existing volumes ?
Or have I misheard the capabilities of the new versions ?
Cheers, Raj.
You should understand implications of it. Fractional reserve allows you to cheat. But if you set it to 10% and in reality need 20%, writing to LUN will fail unless snapshots are deleted (can be done automatically in new versions).
С уважением / With best regards / Mit freundlichen Grüβen
--- Andrey Borzenkov Senior system engineer -----Original Message----- From: owner-toasters@mathworks.com [mailto:owner-toasters@mathworks.com] On Behalf Of Holland, William L Sent: Monday, December 03, 2007 9:25 PM To: Raj Patel Cc: Milazzo Giacomo; toasters@mathworks.com Subject: RE: Can't expand SnapDrive for Windows drive
You can lower it. vol options <volname> fractional_reserve xx
-----Original Message----- From: Raj Patel [mailto:phigmov@gmail.com] Sent: Monday, December 03, 2007 1:02 PM To: Holland, William L Cc: Milazzo Giacomo; toasters@mathworks.com Subject: Re: Can't expand SnapDrive for Windows drive
The default is to have a volume at least twice the size of a LUN to
accomodate at least one full snapshot.
I have heard the new versions of DataOntap and SnapDrive allow for a lower ratio - I'm guessing you can't retrospectively upgrade and reduce the space allocation on existing volumes ?
Or have I misheard the capabilities of the new versions ?
Cheers, Raj.
I think you're thinking of snap reserve, which is an entirely different beast.
Fractional reserve is set to 100% by default. The reason for this is to set aside enough space if you were to overwrite an entire lun. If that happened, your snapshot would be as large as the lun itself. Now, every environment is different, so you can adjust the fractional reserve accordingly, but NetApp best practice is to leave it at 100%.
-----Original Message----- From: Borzenkov, Andrey [mailto:Andrey.Borzenkov@fujitsu-siemens.com] Sent: Tuesday, December 04, 2007 1:50 AM To: Holland, William L; Raj Patel Cc: Milazzo Giacomo; toasters@mathworks.com Subject: RE: Can't expand SnapDrive for Windows drive
You should understand implications of it. Fractional reserve allows you to cheat. But if you set it to 10% and in reality need 20%, writing to LUN will fail unless snapshots are deleted (can be done automatically in new versions).
С уважением / With best regards / Mit freundlichen Grüβen
--- Andrey Borzenkov Senior system engineer -----Original Message----- From: owner-toasters@mathworks.com [mailto:owner-toasters@mathworks.com] On Behalf Of Holland, William L Sent: Monday, December 03, 2007 9:25 PM To: Raj Patel Cc: Milazzo Giacomo; toasters@mathworks.com Subject: RE: Can't expand SnapDrive for Windows drive
You can lower it. vol options <volname> fractional_reserve xx
-----Original Message----- From: Raj Patel [mailto:phigmov@gmail.com] Sent: Monday, December 03, 2007 1:02 PM To: Holland, William L Cc: Milazzo Giacomo; toasters@mathworks.com Subject: Re: Can't expand SnapDrive for Windows drive
The default is to have a volume at least twice the size of a LUN to
accomodate at least one full snapshot.
I have heard the new versions of DataOntap and SnapDrive allow for a lower ratio - I'm guessing you can't retrospectively upgrade and reduce the space allocation on existing volumes ?
Or have I misheard the capabilities of the new versions ?
Cheers, Raj.
What Andrey described is also applicable to Space Reservations\Fractional Reserve. Snap Reserve and Space Reservations essentially serve the same purpose, albeit with different methods:
Snap Reserve reserves a portion of the entire filesystem so that snapshots do not consume active filesystem space (unless they get too large). These are 'per volume'.
Space Reservations reserves a portion of the filesystem _per_file_ so that snapshots do not consume active filesystem space that is needed for an 'overwrite' (WAFL doesn't technically overwrite, ever) of a consumed block in a file\LUN.
Justin, what you described is most certainly why NetApp recommends 100% space reserve - if you have every block in a LUN filled (even if only zeroed out by the attached host, it's still consumed) and take a snapshot, an attempt to overwrite every block within that LUN would be met with an ENOSPACE error if 100% is not available, effectively causing data corruption due to non-committed write.
If you have a proactive environment, you can set the fractional reserve to less than 100% and keep close watch to add space when needed, thereby reducing overall storage consumption/cost initially. If you have a reactive environment, just keep it at 100% and sleep well at night.
Glenn
-----Original Message----- From: owner-toasters@mathworks.com [mailto:owner-toasters@mathworks.com] On Behalf Of Parisi, Justin Sent: Tuesday, December 04, 2007 9:03 AM To: Borzenkov, Andrey; Holland, William L; Raj Patel Cc: Milazzo Giacomo; toasters@mathworks.com Subject: RE: Can't expand SnapDrive for Windows drive
I think you're thinking of snap reserve, which is an entirely different beast.
Fractional reserve is set to 100% by default. The reason for this is to set aside enough space if you were to overwrite an entire lun. If that happened, your snapshot would be as large as the lun itself. Now, every environment is different, so you can adjust the fractional reserve accordingly, but NetApp best practice is to leave it at 100%.
-----Original Message----- From: Borzenkov, Andrey [mailto:Andrey.Borzenkov@fujitsu-siemens.com] Sent: Tuesday, December 04, 2007 1:50 AM To: Holland, William L; Raj Patel Cc: Milazzo Giacomo; toasters@mathworks.com Subject: RE: Can't expand SnapDrive for Windows drive
You should understand implications of it. Fractional reserve allows you to cheat. But if you set it to 10% and in reality need 20%, writing to LUN will fail unless snapshots are deleted (can be done automatically in new versions).
С уважением / With best regards / Mit freundlichen Grüβen
--- Andrey Borzenkov Senior system engineer -----Original Message----- From: owner-toasters@mathworks.com [mailto:owner-toasters@mathworks.com] On Behalf Of Holland, William L Sent: Monday, December 03, 2007 9:25 PM To: Raj Patel Cc: Milazzo Giacomo; toasters@mathworks.com Subject: RE: Can't expand SnapDrive for Windows drive
You can lower it. vol options <volname> fractional_reserve xx
-----Original Message----- From: Raj Patel [mailto:phigmov@gmail.com] Sent: Monday, December 03, 2007 1:02 PM To: Holland, William L Cc: Milazzo Giacomo; toasters@mathworks.com Subject: Re: Can't expand SnapDrive for Windows drive
The default is to have a volume at least twice the size of a LUN to
accomodate at least one full snapshot.
I have heard the new versions of DataOntap and SnapDrive allow for a lower ratio - I'm guessing you can't retrospectively upgrade and reduce the space allocation on existing volumes ?
Or have I misheard the capabilities of the new versions ?
Cheers, Raj.
One more possibility with 7.2 is to set fractional reserve to 0%, snap reserve to some reasonable value, let's say 20%, and configure snapshot autodelete feature for volume in question on snap reserve overflow. This will probably combine the best of two worlds :)
С уважением / With best regards / Mit freundlichen Grüβen
--- Andrey Borzenkov Senior system engineer
-----Original Message----- From: Glenn Walker [mailto:ggwalker@mindspring.com] Sent: Tuesday, December 04, 2007 6:56 PM To: Parisi, Justin; Borzenkov, Andrey; Holland, William L; Raj Patel Cc: Milazzo Giacomo; toasters@mathworks.com Subject: RE: Can't expand SnapDrive for Windows drive
What Andrey described is also applicable to Space Reservations\Fractional Reserve. Snap Reserve and Space Reservations essentially serve the same purpose, albeit with different methods:
Snap Reserve reserves a portion of the entire filesystem so that snapshots do not consume active filesystem space (unless they get too large). These are 'per volume'.
Space Reservations reserves a portion of the filesystem _per_file_ so that snapshots do not consume active filesystem space that is needed for an 'overwrite' (WAFL doesn't technically overwrite, ever) of a consumed block in a file\LUN.
Justin, what you described is most certainly why NetApp recommends 100% space reserve - if you have every block in a LUN filled (even if only zeroed out by the attached host, it's still consumed) and take a snapshot, an attempt to overwrite every block within that LUN would be met with an ENOSPACE error if 100% is not available, effectively causing data corruption due to non-committed write.
If you have a proactive environment, you can set the fractional reserve to less than 100% and keep close watch to add space when needed, thereby reducing overall storage consumption/cost initially. If you have a reactive environment, just keep it at 100% and sleep well at night.
Glenn
-----Original Message----- From: owner-toasters@mathworks.com [mailto:owner-toasters@mathworks.com] On Behalf Of Parisi, Justin Sent: Tuesday, December 04, 2007 9:03 AM To: Borzenkov, Andrey; Holland, William L; Raj Patel Cc: Milazzo Giacomo; toasters@mathworks.com Subject: RE: Can't expand SnapDrive for Windows drive
I think you're thinking of snap reserve, which is an entirely different beast.
Fractional reserve is set to 100% by default. The reason for this is to set aside enough space if you were to overwrite an entire lun. If that happened, your snapshot would be as large as the lun itself. Now, every environment is different, so you can adjust the fractional reserve accordingly, but NetApp best practice is to leave it at 100%.
-----Original Message----- From: Borzenkov, Andrey [mailto:Andrey.Borzenkov@fujitsu-siemens.com] Sent: Tuesday, December 04, 2007 1:50 AM To: Holland, William L; Raj Patel Cc: Milazzo Giacomo; toasters@mathworks.com Subject: RE: Can't expand SnapDrive for Windows drive
You should understand implications of it. Fractional reserve allows you to cheat. But if you set it to 10% and in reality need 20%, writing to LUN will fail unless snapshots are deleted (can be done automatically in new versions).
С уважением / With best regards / Mit freundlichen Grüβen
--- Andrey Borzenkov Senior system engineer -----Original Message----- From: owner-toasters@mathworks.com [mailto:owner-toasters@mathworks.com] On Behalf Of Holland, William L Sent: Monday, December 03, 2007 9:25 PM To: Raj Patel Cc: Milazzo Giacomo; toasters@mathworks.com Subject: RE: Can't expand SnapDrive for Windows drive
You can lower it. vol options <volname> fractional_reserve xx
-----Original Message----- From: Raj Patel [mailto:phigmov@gmail.com] Sent: Monday, December 03, 2007 1:02 PM To: Holland, William L Cc: Milazzo Giacomo; toasters@mathworks.com Subject: Re: Can't expand SnapDrive for Windows drive
The default is to have a volume at least twice the size of a LUN to
accomodate at least one full snapshot.
I have heard the new versions of DataOntap and SnapDrive allow for a lower ratio - I'm guessing you can't retrospectively upgrade and reduce the space allocation on existing volumes ?
Or have I misheard the capabilities of the new versions ?
Cheers, Raj.
My opinion, as from others here, is not to change the fractional reserve and leave it at 100%, then to size volume hosting luns at double of their size. And, last, do not use snapshot autodelete: I've seen tremendous thing happening with this option enabled! :-)
The best way to understand the fractional reserve impact changes see the TR of best practice on SnapManager for Exchange 4 and SnapManager for SQL 2000/2005
-----Messaggio originale----- Da: Borzenkov, Andrey [mailto:Andrey.Borzenkov@fujitsu-siemens.com] Inviato: martedì 4 dicembre 2007 17.04 A: Glenn Walker; Parisi, Justin; Holland, William L; Raj Patel Cc: Milazzo Giacomo; toasters@mathworks.com Oggetto: RE: Can't expand SnapDrive for Windows drive
One more possibility with 7.2 is to set fractional reserve to 0%, snap reserve to some reasonable value, let's say 20%, and configure snapshot autodelete feature for volume in question on snap reserve overflow. This will probably combine the best of two worlds :)
С уважением / With best regards / Mit freundlichen Grüβen
--- Andrey Borzenkov Senior system engineer
-----Original Message----- From: Glenn Walker [mailto:ggwalker@mindspring.com] Sent: Tuesday, December 04, 2007 6:56 PM To: Parisi, Justin; Borzenkov, Andrey; Holland, William L; Raj Patel Cc: Milazzo Giacomo; toasters@mathworks.com Subject: RE: Can't expand SnapDrive for Windows drive
What Andrey described is also applicable to Space Reservations\Fractional Reserve. Snap Reserve and Space Reservations essentially serve the same purpose, albeit with different methods:
Snap Reserve reserves a portion of the entire filesystem so that snapshots do not consume active filesystem space (unless they get too large). These are 'per volume'.
Space Reservations reserves a portion of the filesystem _per_file_ so that snapshots do not consume active filesystem space that is needed for an 'overwrite' (WAFL doesn't technically overwrite, ever) of a consumed block in a file\LUN.
Justin, what you described is most certainly why NetApp recommends 100% space reserve - if you have every block in a LUN filled (even if only zeroed out by the attached host, it's still consumed) and take a snapshot, an attempt to overwrite every block within that LUN would be met with an ENOSPACE error if 100% is not available, effectively causing data corruption due to non-committed write.
If you have a proactive environment, you can set the fractional reserve to less than 100% and keep close watch to add space when needed, thereby reducing overall storage consumption/cost initially. If you have a reactive environment, just keep it at 100% and sleep well at night.
Glenn
-----Original Message----- From: owner-toasters@mathworks.com [mailto:owner-toasters@mathworks.com] On Behalf Of Parisi, Justin Sent: Tuesday, December 04, 2007 9:03 AM To: Borzenkov, Andrey; Holland, William L; Raj Patel Cc: Milazzo Giacomo; toasters@mathworks.com Subject: RE: Can't expand SnapDrive for Windows drive
I think you're thinking of snap reserve, which is an entirely different beast.
Fractional reserve is set to 100% by default. The reason for this is to set aside enough space if you were to overwrite an entire lun. If that happened, your snapshot would be as large as the lun itself. Now, every environment is different, so you can adjust the fractional reserve accordingly, but NetApp best practice is to leave it at 100%.
-----Original Message----- From: Borzenkov, Andrey [mailto:Andrey.Borzenkov@fujitsu-siemens.com] Sent: Tuesday, December 04, 2007 1:50 AM To: Holland, William L; Raj Patel Cc: Milazzo Giacomo; toasters@mathworks.com Subject: RE: Can't expand SnapDrive for Windows drive
You should understand implications of it. Fractional reserve allows you to cheat. But if you set it to 10% and in reality need 20%, writing to LUN will fail unless snapshots are deleted (can be done automatically in new versions).
С уважением / With best regards / Mit freundlichen Grüβen
--- Andrey Borzenkov Senior system engineer -----Original Message----- From: owner-toasters@mathworks.com [mailto:owner-toasters@mathworks.com] On Behalf Of Holland, William L Sent: Monday, December 03, 2007 9:25 PM To: Raj Patel Cc: Milazzo Giacomo; toasters@mathworks.com Subject: RE: Can't expand SnapDrive for Windows drive
You can lower it. vol options <volname> fractional_reserve xx
-----Original Message----- From: Raj Patel [mailto:phigmov@gmail.com] Sent: Monday, December 03, 2007 1:02 PM To: Holland, William L Cc: Milazzo Giacomo; toasters@mathworks.com Subject: Re: Can't expand SnapDrive for Windows drive
The default is to have a volume at least twice the size of a LUN to
accomodate at least one full snapshot.
I have heard the new versions of DataOntap and SnapDrive allow for a lower ratio - I'm guessing you can't retrospectively upgrade and reduce the space allocation on existing volumes ?
Or have I misheard the capabilities of the new versions ?
Cheers, Raj.
Actually, this document is the best way to understand reserves and guarantees: http://now.netapp.com/NOW/knowledge/docs/ontap/rel723/pdfs/ontap/bsag.pdf
Use it as your bible for these sorts of things. It's not light reading, but very useful.
-----Original Message----- From: Milazzo Giacomo [mailto:G.Milazzo@sinergy.it] Sent: Tuesday, December 04, 2007 11:12 AM To: Borzenkov, Andrey; Glenn Walker; Parisi, Justin; Holland, William L; Raj Patel Cc: toasters@mathworks.com Subject: R: Can't expand SnapDrive for Windows drive
My opinion, as from others here, is not to change the fractional reserve and leave it at 100%, then to size volume hosting luns at double of their size. And, last, do not use snapshot autodelete: I've seen tremendous thing happening with this option enabled! :-)
The best way to understand the fractional reserve impact changes see the TR of best practice on SnapManager for Exchange 4 and SnapManager for SQL 2000/2005
-----Messaggio originale----- Da: Borzenkov, Andrey [mailto:Andrey.Borzenkov@fujitsu-siemens.com] Inviato: martedì 4 dicembre 2007 17.04 A: Glenn Walker; Parisi, Justin; Holland, William L; Raj Patel Cc: Milazzo Giacomo; toasters@mathworks.com Oggetto: RE: Can't expand SnapDrive for Windows drive
One more possibility with 7.2 is to set fractional reserve to 0%, snap reserve to some reasonable value, let's say 20%, and configure snapshot autodelete feature for volume in question on snap reserve overflow. This will probably combine the best of two worlds :)
С уважением / With best regards / Mit freundlichen Grüβen
--- Andrey Borzenkov Senior system engineer
-----Original Message----- From: Glenn Walker [mailto:ggwalker@mindspring.com] Sent: Tuesday, December 04, 2007 6:56 PM To: Parisi, Justin; Borzenkov, Andrey; Holland, William L; Raj Patel Cc: Milazzo Giacomo; toasters@mathworks.com Subject: RE: Can't expand SnapDrive for Windows drive
What Andrey described is also applicable to Space Reservations\Fractional Reserve. Snap Reserve and Space Reservations essentially serve the same purpose, albeit with different methods:
Snap Reserve reserves a portion of the entire filesystem so that snapshots do not consume active filesystem space (unless they get too large). These are 'per volume'.
Space Reservations reserves a portion of the filesystem _per_file_ so that snapshots do not consume active filesystem space that is needed for an 'overwrite' (WAFL doesn't technically overwrite, ever) of a consumed block in a file\LUN.
Justin, what you described is most certainly why NetApp recommends 100% space reserve - if you have every block in a LUN filled (even if only zeroed out by the attached host, it's still consumed) and take a snapshot, an attempt to overwrite every block within that LUN would be met with an ENOSPACE error if 100% is not available, effectively causing data corruption due to non-committed write.
If you have a proactive environment, you can set the fractional reserve to less than 100% and keep close watch to add space when needed, thereby reducing overall storage consumption/cost initially. If you have a reactive environment, just keep it at 100% and sleep well at night.
Glenn
-----Original Message----- From: owner-toasters@mathworks.com [mailto:owner-toasters@mathworks.com] On Behalf Of Parisi, Justin Sent: Tuesday, December 04, 2007 9:03 AM To: Borzenkov, Andrey; Holland, William L; Raj Patel Cc: Milazzo Giacomo; toasters@mathworks.com Subject: RE: Can't expand SnapDrive for Windows drive
I think you're thinking of snap reserve, which is an entirely different beast.
Fractional reserve is set to 100% by default. The reason for this is to set aside enough space if you were to overwrite an entire lun. If that happened, your snapshot would be as large as the lun itself. Now, every environment is different, so you can adjust the fractional reserve accordingly, but NetApp best practice is to leave it at 100%.
-----Original Message----- From: Borzenkov, Andrey [mailto:Andrey.Borzenkov@fujitsu-siemens.com] Sent: Tuesday, December 04, 2007 1:50 AM To: Holland, William L; Raj Patel Cc: Milazzo Giacomo; toasters@mathworks.com Subject: RE: Can't expand SnapDrive for Windows drive
You should understand implications of it. Fractional reserve allows you to cheat. But if you set it to 10% and in reality need 20%, writing to LUN will fail unless snapshots are deleted (can be done automatically in new versions).
С уважением / With best regards / Mit freundlichen Grüβen
--- Andrey Borzenkov Senior system engineer -----Original Message----- From: owner-toasters@mathworks.com [mailto:owner-toasters@mathworks.com] On Behalf Of Holland, William L Sent: Monday, December 03, 2007 9:25 PM To: Raj Patel Cc: Milazzo Giacomo; toasters@mathworks.com Subject: RE: Can't expand SnapDrive for Windows drive
You can lower it. vol options <volname> fractional_reserve xx
-----Original Message----- From: Raj Patel [mailto:phigmov@gmail.com] Sent: Monday, December 03, 2007 1:02 PM To: Holland, William L Cc: Milazzo Giacomo; toasters@mathworks.com Subject: Re: Can't expand SnapDrive for Windows drive
The default is to have a volume at least twice the size of a LUN to
accomodate at least one full snapshot.
I have heard the new versions of DataOntap and SnapDrive allow for a lower ratio - I'm guessing you can't retrospectively upgrade and reduce the space allocation on existing volumes ?
Or have I misheard the capabilities of the new versions ?
Cheers, Raj.
SnapDrive will enforce that snap reserve is set to zero, so that probably won't work really well. The Snapshot Autodelete doesn't have to have snap reserve set - the snapshots are accounted for the in the space reservation pool, so using snapshot autodelete will still reduce the consumption of the space reserve and give you the same results you're looking for.
-----Original Message----- From: Borzenkov, Andrey [mailto:Andrey.Borzenkov@fujitsu-siemens.com] Sent: Tuesday, December 04, 2007 11:04 AM To: Glenn Walker; Parisi, Justin; Holland, William L; Raj Patel Cc: Milazzo Giacomo; toasters@mathworks.com Subject: RE: Can't expand SnapDrive for Windows drive
One more possibility with 7.2 is to set fractional reserve to 0%, snap reserve to some reasonable value, let's say 20%, and configure snapshot autodelete feature for volume in question on snap reserve overflow. This will probably combine the best of two worlds :)
С уважением / With best regards / Mit freundlichen Grüβen
--- Andrey Borzenkov Senior system engineer
-----Original Message----- From: Glenn Walker [mailto:ggwalker@mindspring.com] Sent: Tuesday, December 04, 2007 6:56 PM To: Parisi, Justin; Borzenkov, Andrey; Holland, William L; Raj Patel Cc: Milazzo Giacomo; toasters@mathworks.com Subject: RE: Can't expand SnapDrive for Windows drive
What Andrey described is also applicable to Space Reservations\Fractional Reserve. Snap Reserve and Space Reservations essentially serve the same purpose, albeit with different methods:
Snap Reserve reserves a portion of the entire filesystem so that snapshots do not consume active filesystem space (unless they get too large). These are 'per volume'.
Space Reservations reserves a portion of the filesystem _per_file_ so that snapshots do not consume active filesystem space that is needed for an 'overwrite' (WAFL doesn't technically overwrite, ever) of a consumed block in a file\LUN.
Justin, what you described is most certainly why NetApp recommends 100% space reserve - if you have every block in a LUN filled (even if only zeroed out by the attached host, it's still consumed) and take a snapshot, an attempt to overwrite every block within that LUN would be met with an ENOSPACE error if 100% is not available, effectively causing data corruption due to non-committed write.
If you have a proactive environment, you can set the fractional reserve to less than 100% and keep close watch to add space when needed, thereby reducing overall storage consumption/cost initially. If you have a reactive environment, just keep it at 100% and sleep well at night.
Glenn
-----Original Message----- From: owner-toasters@mathworks.com [mailto:owner-toasters@mathworks.com] On Behalf Of Parisi, Justin Sent: Tuesday, December 04, 2007 9:03 AM To: Borzenkov, Andrey; Holland, William L; Raj Patel Cc: Milazzo Giacomo; toasters@mathworks.com Subject: RE: Can't expand SnapDrive for Windows drive
I think you're thinking of snap reserve, which is an entirely different beast.
Fractional reserve is set to 100% by default. The reason for this is to set aside enough space if you were to overwrite an entire lun. If that happened, your snapshot would be as large as the lun itself. Now, every environment is different, so you can adjust the fractional reserve accordingly, but NetApp best practice is to leave it at 100%.
-----Original Message----- From: Borzenkov, Andrey [mailto:Andrey.Borzenkov@fujitsu-siemens.com] Sent: Tuesday, December 04, 2007 1:50 AM To: Holland, William L; Raj Patel Cc: Milazzo Giacomo; toasters@mathworks.com Subject: RE: Can't expand SnapDrive for Windows drive
You should understand implications of it. Fractional reserve allows you to cheat. But if you set it to 10% and in reality need 20%, writing to LUN will fail unless snapshots are deleted (can be done automatically in new versions).
С уважением / With best regards / Mit freundlichen Grüβen
--- Andrey Borzenkov Senior system engineer -----Original Message----- From: owner-toasters@mathworks.com [mailto:owner-toasters@mathworks.com] On Behalf Of Holland, William L Sent: Monday, December 03, 2007 9:25 PM To: Raj Patel Cc: Milazzo Giacomo; toasters@mathworks.com Subject: RE: Can't expand SnapDrive for Windows drive
You can lower it. vol options <volname> fractional_reserve xx
-----Original Message----- From: Raj Patel [mailto:phigmov@gmail.com] Sent: Monday, December 03, 2007 1:02 PM To: Holland, William L Cc: Milazzo Giacomo; toasters@mathworks.com Subject: Re: Can't expand SnapDrive for Windows drive
The default is to have a volume at least twice the size of a LUN to
accomodate at least one full snapshot.
I have heard the new versions of DataOntap and SnapDrive allow for a lower ratio - I'm guessing you can't retrospectively upgrade and reduce the space allocation on existing volumes ?
Or have I misheard the capabilities of the new versions ?
Cheers, Raj.
You can upgrade and change the fractional reserve, then shrink the volumes.
-----Original Message----- From: owner-toasters@mathworks.com [mailto:owner-toasters@mathworks.com] On Behalf Of Raj Patel Sent: Monday, December 03, 2007 1:02 PM To: Holland, William L Cc: Milazzo Giacomo; toasters@mathworks.com Subject: Re: Can't expand SnapDrive for Windows drive
The default is to have a volume at least twice the size of a LUN to
accomodate at least one full snapshot.
I have heard the new versions of DataOntap and SnapDrive allow for a lower ratio - I'm guessing you can't retrospectively upgrade and reduce the space allocation on existing volumes ?
Or have I misheard the capabilities of the new versions ?
Cheers, Raj.
-
Borzenkov, Andrey -
Glenn Walker -
Holland, William L -
Milazzo Giacomo -
Parisi, Justin -
Raj Patel