Remember that WAFL still writes across the entire aggregate. Having a slower RAID group in an aggregate of faster raid groups would be akin to having a slower disk in a RG of faster disks, would it not?
Glenn
________________________________
From: owner-toasters@mathworks.com [mailto:owner-toasters@mathworks.com] On Behalf Of Brosseau, Paul Sent: Wednesday, September 20, 2006 8:05 PM To: Jeff Mery; toasters@mathworks.com Subject: RE: Mixed disk sizes within a single aggregate
Mixing disk sizes in an aggregate is not a problem as long as you create RAID groups for each kind of disk. WAFL creates stripes at the RAID group level. For best results create complete RAID groups each time you add disks to an aggregate.
Paulb
________________________________
From: Jeff Mery [mailto:jeff.mery@ni.com] Sent: Wednesday, September 20, 2006 3:30 PM To: toasters@mathworks.com Subject: Mixed disk sizes within a single aggregate
Greetings fellow toasters! <Background> We're looking at moving our 2 FAS940 systems from tradtional volumes to flexvols + aggregates. </Background>
It would seem to me that the same rules and guidelines for creating traditional volumes now apply directly to the aggregate level (for the most part). By rules and guidelines I mean things like trying not to mix disk sizes, try to avoid volumes (now aggregates?) that span FC adapters, etc.
Are any of these things still a concern on modern versions of ONTAP (7+)? Does anyone have any best practices they'd be willing to share in regards to aggregate creation? NOW says "make them as big as possible using as many spindles as possible", but that doesn't really help much. We use our filers for unstructured data only; cifs + nfs but no databases, no snapmirror, no snapvault, etc..
TIA, Jeff Mery - MCSE, MCP National Instruments
------------------------------------------------------------------------ - "Allow me to extol the virtues of the Net Fairy, and of all the fantastic dorks that make the nice packets go from here to there. Amen." TB - Penny Arcade ------------------------------------------------------------------------ -
I think wafl stripes across all disks in an aggregate. I'm not sure how it respond to having one raid group with larger disks - likely it will not use part of them. I'm pretty sure netapp recommends all disks in an aggregate be the same size, or, it will assume they are all the size of the smallest disk. Of course, I could be wrong . . .
David
Remember that WAFL still writes across the entire aggregate. Having a slower RAID group in an aggregate of faster raid groups would be akin to having a slower disk in a RG of faster disks, would it not?
Glenn
From: owner-toasters@mathworks.com [mailto:owner-toasters@mathworks.com] On Behalf Of Brosseau, Paul Sent: Wednesday, September 20, 2006 8:05 PM To: Jeff Mery; toasters@mathworks.com Subject: RE: Mixed disk sizes within a single aggregate
Mixing disk sizes in an aggregate is not a problem as long as you create RAID groups for each kind of disk. WAFL creates stripes at the RAID group level. For best results create complete RAID groups each time you add disks to an aggregate.
Paulb
From: Jeff Mery [mailto:jeff.mery@ni.com] Sent: Wednesday, September 20, 2006 3:30 PM To: toasters@mathworks.com Subject: Mixed disk sizes within a single aggregate
Greetings fellow toasters!
<Background> We're looking at moving our 2 FAS940 systems from tradtional volumes to flexvols + aggregates. </Background>
It would seem to me that the same rules and guidelines for creating traditional volumes now apply directly to the aggregate level (for the most part). By rules and guidelines I mean things like trying not to mix disk sizes, try to avoid volumes (now aggregates?) that span FC adapters, etc.
Are any of these things still a concern on modern versions of ONTAP (7+)? Does anyone have any best practices they'd be willing to share in regards to aggregate creation? NOW says "make them as big as possible using as many spindles as possible", but that doesn't really help much. We use our filers for unstructured data only; cifs + nfs but no databases, no snapmirror, no snapvault, etc..
TIA, Jeff Mery - MCSE, MCP National Instruments
"Allow me to extol the virtues of the Net Fairy, and of all the fantastic dorks that make the nice packets go from here to there. Amen." TB - Penny Arcade
Thanks for the responses everyone. Just to confirm...
...WAFL does indeed stripe each flexvol across all disks in the aggregate. If you have a flexvol that's 5% of your total aggregate space, it's safe to conclude that it's using 5% of each disk in your aggregate (assuming aggregate disks are all the same size). This was the impression I got from the documentation and then confirmed by the group.
...We don't have any mixed performance disks in our system (everything is 10K RPM), just mixed sizes. Creating a separate RG for each disk size is a good idea; this prevents wasting any larger disks on parity for smaller ones. Thanks for the suggestion.
It seems we still have some confusion around what happens with performance in this mixed-disk scenario as well as the impact of a single aggregate spanning multiple FC adapters. Can anyone from NetApp clarify these for us?
Jeff Mery - MCSE, MCP National Instruments
------------------------------------------------------------------------- "Allow me to extol the virtues of the Net Fairy, and of all the fantastic dorks that make the nice packets go from here to there. Amen." TB - Penny Arcade -------------------------------------------------------------------------
David Knight knight@atmos.albany.edu 09/21/2006 08:43 AM
To ggwalker@mindspring.com (Glenn Walker) cc Paul.Brosseau@netapp.com, jeff.mery@ni.com, toasters@mathworks.com Subject Re: Mixed disk sizes within a single aggregate
I think wafl stripes across all disks in an aggregate. I'm not sure how it respond to having one raid group with larger disks - likely it will not use part of them. I'm pretty sure netapp recommends all disks in an aggregate be the same size, or, it will assume they are all the size of the smallest disk. Of course, I could be wrong . . .
David
Remember that WAFL still writes across the entire aggregate. Having a slower RAID group in an aggregate of faster raid groups would be akin to having a slower disk in a RG of faster disks, would it not?
Glenn
From: owner-toasters@mathworks.com [mailto:owner-toasters@mathworks.com] On Behalf Of Brosseau, Paul Sent: Wednesday, September 20, 2006 8:05 PM To: Jeff Mery; toasters@mathworks.com Subject: RE: Mixed disk sizes within a single aggregate
Mixing disk sizes in an aggregate is not a problem as long as you create RAID groups for each kind of disk. WAFL creates stripes at the RAID group level. For best results create complete RAID groups each time you add disks to an aggregate.
Paulb
From: Jeff Mery [mailto:jeff.mery@ni.com] Sent: Wednesday, September 20, 2006 3:30 PM To: toasters@mathworks.com Subject: Mixed disk sizes within a single aggregate
Greetings fellow toasters!
<Background> We're looking at moving our 2 FAS940 systems from tradtional volumes to flexvols + aggregates. </Background>
It would seem to me that the same rules and guidelines for creating traditional volumes now apply directly to the aggregate level (for the most part). By rules and guidelines I mean things like trying not to mix disk sizes, try to avoid volumes (now aggregates?) that span FC adapters, etc.
Are any of these things still a concern on modern versions of ONTAP (7+)? Does anyone have any best practices they'd be willing to share in regards to aggregate creation? NOW says "make them as big as possible using as many spindles as possible", but that doesn't really help much. We use our filers for unstructured data only; cifs + nfs but no databases, no snapmirror, no snapvault, etc..
TIA, Jeff Mery - MCSE, MCP National Instruments
"Allow me to extol the virtues of the Net Fairy, and of all the fantastic dorks that make the nice packets go from here to there. Amen." TB - Penny Arcade
Most workloads are not going to reach 2gbit fibrechannel saturation, except with the occasional disk reconstruction. With that in mind, you'll want to spread your raidgroups across as many loops as possible and within budget.
Concerning different sized 10k rpm disks, just realize that since 144GB disks are larger than 72GB disks, you will eventually have more data on the 144GB raid group, so generally you will see more I/O toward that set of disks, but the RPM is the same, and the performance characteristics are basically identical.
On Thu, 21 Sep 2006, Jeff Mery wrote:
Thanks for the responses everyone. Just to confirm...
...WAFL does indeed stripe each flexvol across all disks in the aggregate. If you have a flexvol that's 5% of your total aggregate space, it's safe to conclude that it's using 5% of each disk in your aggregate (assuming aggregate disks are all the same size). This was the impression I got from the documentation and then confirmed by the group.
...We don't have any mixed performance disks in our system (everything is 10K RPM), just mixed sizes. Creating a separate RG for each disk size is a good idea; this prevents wasting any larger disks on parity for smaller ones. Thanks for the suggestion.
It seems we still have some confusion around what happens with performance in this mixed-disk scenario as well as the impact of a single aggregate spanning multiple FC adapters. Can anyone from NetApp clarify these for us?
Jeff Mery - MCSE, MCP National Instruments
------------------------------------------------------------------------- "Allow me to extol the virtues of the Net Fairy, and of all the fantastic dorks that make the nice packets go from here to there. Amen." TB - Penny Arcade -------------------------------------------------------------------------
David Knight knight@atmos.albany.edu 09/21/2006 08:43 AM
To ggwalker@mindspring.com (Glenn Walker) cc Paul.Brosseau@netapp.com, jeff.mery@ni.com, toasters@mathworks.com Subject Re: Mixed disk sizes within a single aggregate
I think wafl stripes across all disks in an aggregate. I'm not sure how it respond to having one raid group with larger disks - likely it will not use part of them. I'm pretty sure netapp recommends all disks in an aggregate be the same size, or, it will assume they are all the size of the smallest disk. Of course, I could be wrong . . .
David
Remember that WAFL still writes across the entire aggregate. Having a slower RAID group in an aggregate of faster raid groups would be akin to having a slower disk in a RG of faster disks, would it not?
Glenn
From: owner-toasters@mathworks.com [mailto:owner-toasters@mathworks.com] On Behalf Of Brosseau, Paul Sent: Wednesday, September 20, 2006 8:05 PM To: Jeff Mery; toasters@mathworks.com Subject: RE: Mixed disk sizes within a single aggregate
Mixing disk sizes in an aggregate is not a problem as long as you create RAID groups for each kind of disk. WAFL creates stripes at the RAID group level. For best results create complete RAID groups each time you add disks to an aggregate.
Paulb
From: Jeff Mery [mailto:jeff.mery@ni.com] Sent: Wednesday, September 20, 2006 3:30 PM To: toasters@mathworks.com Subject: Mixed disk sizes within a single aggregate
Greetings fellow toasters!
<Background> We're looking at moving our 2 FAS940 systems from tradtional volumes to flexvols + aggregates. </Background>
It would seem to me that the same rules and guidelines for creating traditional volumes now apply directly to the aggregate level (for the most part). By rules and guidelines I mean things like trying not to mix disk sizes, try to avoid volumes (now aggregates?) that span FC adapters, etc.
Are any of these things still a concern on modern versions of ONTAP (7+)? Does anyone have any best practices they'd be willing to share in regards to aggregate creation? NOW says "make them as big as possible using as many spindles as possible", but that doesn't really help much. We use our filers for unstructured data only; cifs + nfs but no databases, no snapmirror, no snapvault, etc..
TIA, Jeff Mery - MCSE, MCP National Instruments
"Allow me to extol the virtues of the Net Fairy, and of all the fantastic dorks that make the nice packets go from here to there. Amen." TB - Penny Arcade
I think wafl stripes across all disks in an aggregate. I'm not sure how it respond to having one raid group with larger disks - likely it will not use part of them. I'm pretty sure netapp recommends all disks in an aggregate be the same size, or, it will assume they are all the size of the smallest disk. Of course, I could be wrong . . .
David
No, WAFL only stripes across disks in the same RG. However, WAFL will use stripes from all RGs in an aggregate when storing a flex vol, so that is why a flex vol gets spread out over all the disks.
Furthermore, it is possible for multiple flex vols to have data in the same stripe, so stripes are not "owned" by any paricular flex vol. Basically, the aggregate mixes up all the data rather arbitarily, hence the "Anywhere" in W.A.F.L.
Perhaps you are thinking about a RG composed of different sized disks. In this case it is possible that space is wasted on the larger disks, but I'm not 100% sure.
Steve Losen scl@virginia.edu phone: 434-924-0640
University of Virginia ITC Unix Support
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David Knight -
Glenn Walker -
Jeff Mery -
Myles Uyema -
Stephen C. Losen