Can I sanity check something?
I've got a cluster in a box - in the form of a 2240-4. Single shelf, but it's got 4 SSDs installed.
Which works as two per head.
Looking at it, I can't actually configure a hybrid aggregate, because I have to match RAID types (RAID-DP on two drives doesn't work). That's on my current code rev of 8.1.3
Upgrading to 8.2 might be a solution, because then I could RAID4 my SSDs.
But I'm wondering - what happens, given a system with no spares, one of the SSDs dies? (Or indeed, whether running with no spares is actually a good idea in the first place - I do have spares for my SAS drives, but not SSDs).
With that in mind - am I onto a bit of a loser here? And I should just be looking to replace my SSDs with some drives to match what I've got already?
Or perhaps have one head with flashpool, 3 drives + spare and one without?
I’d do 1 head with a flashpool and one without.
From: Edward Rolison ed.rolison@gmail.commailto:ed.rolison@gmail.com> Date: Thursday, 19 February 2015 15:39 To: "toasters@teaparty.netmailto:toasters@teaparty.net" toasters@teaparty.netmailto:toasters@teaparty.net> Subject: FAS2240-4 'cluster' with 4 SSDs
Can I sanity check something?
I've got a cluster in a box - in the form of a 2240-4. Single shelf, but it's got 4 SSDs installed.
Which works as two per head.
Looking at it, I can't actually configure a hybrid aggregate, because I have to match RAID types (RAID-DP on two drives doesn't work). That's on my current code rev of 8.1.3
Upgrading to 8.2 might be a solution, because then I could RAID4 my SSDs.
But I'm wondering - what happens, given a system with no spares, one of the SSDs dies? (Or indeed, whether running with no spares is actually a good idea in the first place - I do have spares for my SAS drives, but not SSDs).
With that in mind - am I onto a bit of a loser here? And I should just be looking to replace my SSDs with some drives to match what I've got already?
Or perhaps have one head with flashpool, 3 drives + spare and one without?
Ed Morgan Technical Consultant
T: M:07875 628794 E: ed.morgan@ansgroup.co.uk
Disclaimer The information contained in this communication from ed.morgan@ansgroup.co.uk sent at 2015-02-1915:48:18 is confidential and may be legally privileged. It is intended solely for use by toasters@teaparty.net and others authorised to receive it. If you are not toasters@teaparty.net you are hereby notified that any disclosure, copying,distribution or taking action in reliance of the contents of this information is strictly prohibited and may be unlawful. ANS Group Plc Terms & Conditions apply, all prices are subject to VAT, expenses excluded,E&O,E.
ANS Group Plc, Registered Office is Synergy House, Manchester Science Park, Manchester, M15 6SY. Reg No. 3176761. (Registered in England & Wales)
I try not to use raid4 in FlashPools. Using raid4 may increase the amount of usable cache size, but this means your SSD raidgroup becomes the weakest link in the aggregate. I would assign all SSD's to one of the nodes and create one SSD raid_dp raigroup.
Mvg, Wouter Vervloesem
Neoria - Uptime Group Veldkant 35D B-2550 Kontich
Tel: +32 (0)3 451 23 82 Mailto: wouter.vervloesem@neoria.be Web: http://www.neoria.be
Op 19-feb.-2015, om 16:48 heeft Ed Morgan Ed.Morgan@ansgroup.co.uk het volgende geschreven:
I’d do 1 head with a flashpool and one without.
From: Edward Rolison ed.rolison@gmail.com Date: Thursday, 19 February 2015 15:39 To: "toasters@teaparty.net" toasters@teaparty.net Subject: FAS2240-4 'cluster' with 4 SSDs
Can I sanity check something?
I've got a cluster in a box - in the form of a 2240-4. Single shelf, but it's got 4 SSDs installed.
Which works as two per head.
Looking at it, I can't actually configure a hybrid aggregate, because I have to match RAID types (RAID-DP on two drives doesn't work). That's on my current code rev of 8.1.3
Upgrading to 8.2 might be a solution, because then I could RAID4 my SSDs.
But I'm wondering - what happens, given a system with no spares, one of the SSDs dies? (Or indeed, whether running with no spares is actually a good idea in the first place - I do have spares for my SAS drives, but not SSDs).
With that in mind - am I onto a bit of a loser here? And I should just be looking to replace my SSDs with some drives to match what I've got already?
Or perhaps have one head with flashpool, 3 drives + spare and one without?
Ed Morgan | Technical Consultant <115021915481801802.jpeg> T: M: 07875 628794 E: ed.morgan@ansgroup.co.uk ANS Group London Office 18 King William Street, London, EC4N 7BP www.ans.co.uk
<115021915481802002.png>
<115021915481801802.jpeg> Disclaimer : The information contained in this communication from Ed Morgan sent on 2015-02-19 at 15:48:18 is confidential and may be legally privileged. It is intended solely for use by toasters@teaparty.net and others authorised to receive it. If you are not toasters@teaparty.net you are hereby notified that any disclosure, copying, distribution or taking action in reliance of the contents of this information is strictly prohibited and may be unlawful. ANS Group plc Terms & Conditions apply, All Prices are subject to VAT, Expenses excluded, E&OE
ANS Group Plc - Privacy Policy - Registered Office is Synergy House, Manchester Science Park, Manchester, M15 6SY. Reg No. 3176761. (Registered in England & Wales) _______________________________________________ Toasters mailing list Toasters@teaparty.net http://www.teaparty.net/mailman/listinfo/toasters
I'm not overly keen on the concept - these systems aren't particularly performance critical, so can do without. What I'm not clear on is just how weak a link a two drive/no spare RAID4 flashpool would actually be.
I mean, I don't like running without spares at all, but given I believe the flash pool is used like a cache (e.g. not a unique copy, but a replica) is that as much of a risk?
On 19 February 2015 at 16:32, Vervloesem Wouter <wouter.vervloesem@neoria.be
wrote:
I try not to use raid4 in FlashPools. Using raid4 may increase the amount of usable cache size, but this means your SSD raidgroup becomes the weakest link in the aggregate. I would assign all SSD's to one of the nodes and create one SSD raid_dp raigroup.
Mvg, Wouter Vervloesem
Neoria - Uptime Group Veldkant 35D B-2550 Kontich
Tel: +32 (0)3 451 23 82 Mailto: wouter.vervloesem@neoria.be Web: http://www.neoria.be
Op 19-feb.-2015, om 16:48 heeft Ed Morgan Ed.Morgan@ansgroup.co.uk
het volgende geschreven:
I’d do 1 head with a flashpool and one without.
From: Edward Rolison ed.rolison@gmail.com Date: Thursday, 19 February 2015 15:39 To: "toasters@teaparty.net" toasters@teaparty.net Subject: FAS2240-4 'cluster' with 4 SSDs
Can I sanity check something?
I've got a cluster in a box - in the form of a 2240-4. Single shelf, but
it's got 4 SSDs installed.
Which works as two per head.
Looking at it, I can't actually configure a hybrid aggregate, because I
have to match RAID types (RAID-DP on two drives doesn't work). That's on my current code rev of 8.1.3
Upgrading to 8.2 might be a solution, because then I could RAID4 my SSDs.
But I'm wondering - what happens, given a system with no spares, one of
the SSDs dies? (Or indeed, whether running with no spares is actually a good idea in the first place - I do have spares for my SAS drives, but not SSDs).
With that in mind - am I onto a bit of a loser here? And I should just
be looking to replace my SSDs with some drives to match what I've got already?
Or perhaps have one head with flashpool, 3 drives + spare and one
without?
Ed Morgan | Technical Consultant <115021915481801802.jpeg> T: M: 07875 628794 E: ed.morgan@ansgroup.co.uk ANS Group London Office 18 King William Street, London, EC4N 7BP www.ans.co.uk
<115021915481802002.png>
<115021915481801802.jpeg> Disclaimer : The information contained in this communication from Ed
Morgan sent on 2015-02-19 at 15:48:18 is confidential and may be legally privileged. It is intended solely for use by toasters@teaparty.net and others authorised to receive it. If you are not toasters@teaparty.net you are hereby notified that any disclosure, copying, distribution or taking action in reliance of the contents of this information is strictly prohibited and may be unlawful. ANS Group plc Terms & Conditions apply, All Prices are subject to VAT, Expenses excluded, E&OE
ANS Group Plc - Privacy Policy - Registered Office is Synergy House,
Manchester Science Park, Manchester, M15 6SY. Reg No. 3176761. (Registered in England & Wales)
Toasters mailing list Toasters@teaparty.net http://www.teaparty.net/mailman/listinfo/toasters
If you don't protect the SSDs and there's a failure, you'll lose data and corrupt the aggregate, I think. For flash pool, at least.
On Thu, Feb 19, 2015 at 11:38 AM, Edward Rolison ed.rolison@gmail.com wrote:
I'm not overly keen on the concept - these systems aren't particularly performance critical, so can do without. What I'm not clear on is just how weak a link a two drive/no spare RAID4 flashpool would actually be.
I mean, I don't like running without spares at all, but given I believe the flash pool is used like a cache (e.g. not a unique copy, but a replica) is that as much of a risk?
On 19 February 2015 at 16:32, Vervloesem Wouter < wouter.vervloesem@neoria.be> wrote:
I try not to use raid4 in FlashPools. Using raid4 may increase the amount of usable cache size, but this means your SSD raidgroup becomes the weakest link in the aggregate. I would assign all SSD's to one of the nodes and create one SSD raid_dp raigroup.
Mvg, Wouter Vervloesem
Neoria - Uptime Group Veldkant 35D B-2550 Kontich
Tel: +32 (0)3 451 23 82 Mailto: wouter.vervloesem@neoria.be Web: http://www.neoria.be
Op 19-feb.-2015, om 16:48 heeft Ed Morgan Ed.Morgan@ansgroup.co.uk
het volgende geschreven:
I’d do 1 head with a flashpool and one without.
From: Edward Rolison ed.rolison@gmail.com Date: Thursday, 19 February 2015 15:39 To: "toasters@teaparty.net" toasters@teaparty.net Subject: FAS2240-4 'cluster' with 4 SSDs
Can I sanity check something?
I've got a cluster in a box - in the form of a 2240-4. Single shelf,
but it's got 4 SSDs installed.
Which works as two per head.
Looking at it, I can't actually configure a hybrid aggregate, because I
have to match RAID types (RAID-DP on two drives doesn't work). That's on my current code rev of 8.1.3
Upgrading to 8.2 might be a solution, because then I could RAID4 my
SSDs.
But I'm wondering - what happens, given a system with no spares, one of
the SSDs dies? (Or indeed, whether running with no spares is actually a good idea in the first place - I do have spares for my SAS drives, but not SSDs).
With that in mind - am I onto a bit of a loser here? And I should just
be looking to replace my SSDs with some drives to match what I've got already?
Or perhaps have one head with flashpool, 3 drives + spare and one
without?
Ed Morgan | Technical Consultant <115021915481801802.jpeg> T: M: 07875 628794 E: ed.morgan@ansgroup.co.uk ANS Group London Office 18 King William Street, London, EC4N 7BP www.ans.co.uk
<115021915481802002.png>
<115021915481801802.jpeg> Disclaimer : The information contained in this communication from Ed
Morgan sent on 2015-02-19 at 15:48:18 is confidential and may be legally privileged. It is intended solely for use by toasters@teaparty.net and others authorised to receive it. If you are not toasters@teaparty.net you are hereby notified that any disclosure, copying, distribution or taking action in reliance of the contents of this information is strictly prohibited and may be unlawful. ANS Group plc Terms & Conditions apply, All Prices are subject to VAT, Expenses excluded, E&OE
ANS Group Plc - Privacy Policy - Registered Office is Synergy House,
Manchester Science Park, Manchester, M15 6SY. Reg No. 3176761. (Registered in England & Wales)
Toasters mailing list Toasters@teaparty.net http://www.teaparty.net/mailman/listinfo/toasters
Toasters mailing list Toasters@teaparty.net http://www.teaparty.net/mailman/listinfo/toasters
I think you would be okay with RAID4, 2 data disk, 1 parity and 1 spare.
Due to the size and speed of SSD, rebuilds are much faster so this is a much more resilient configuration than it would be with a similar configuration and spinning drives. In addition, with the raid group being so small having only 1 spare and 1 parity disk is not such a big deal. I certainly would not recommend no spares as the fact that you can rebuild a failed disk to a hot spare in under a few hours is an important part of the resiliency.
--JMS
From: toasters-bounces@teaparty.net [mailto:toasters-bounces@teaparty.net] On Behalf Of Basil Sent: Thursday, February 19, 2015 12:14 PM To: Edward Rolison Cc: toasters@teaparty.net Subject: Re: FAS2240-4 'cluster' with 4 SSDs
If you don't protect the SSDs and there's a failure, you'll lose data and corrupt the aggregate, I think. For flash pool, at least.
On Thu, Feb 19, 2015 at 11:38 AM, Edward Rolison <ed.rolison@gmail.commailto:ed.rolison@gmail.com> wrote: I'm not overly keen on the concept - these systems aren't particularly performance critical, so can do without. What I'm not clear on is just how weak a link a two drive/no spare RAID4 flashpool would actually be.
I mean, I don't like running without spares at all, but given I believe the flash pool is used like a cache (e.g. not a unique copy, but a replica) is that as much of a risk?
On 19 February 2015 at 16:32, Vervloesem Wouter <wouter.vervloesem@neoria.bemailto:wouter.vervloesem@neoria.be> wrote: I try not to use raid4 in FlashPools. Using raid4 may increase the amount of usable cache size, but this means your SSD raidgroup becomes the weakest link in the aggregate. I would assign all SSD's to one of the nodes and create one SSD raid_dp raigroup.
Mvg, Wouter Vervloesem
Neoria - Uptime Group Veldkant 35D B-2550 Kontich
Tel: +32 (0)3 451 23 82tel:%2B32%20%280%293%20451%2023%2082 Mailto: wouter.vervloesem@neoria.bemailto:wouter.vervloesem@neoria.be Web: http://www.neoria.be
Op 19-feb.-2015, om 16:48 heeft Ed Morgan <Ed.Morgan@ansgroup.co.ukmailto:Ed.Morgan@ansgroup.co.uk> het volgende geschreven:
I’d do 1 head with a flashpool and one without.
From: Edward Rolison <ed.rolison@gmail.commailto:ed.rolison@gmail.com> Date: Thursday, 19 February 2015 15:39 To: "toasters@teaparty.netmailto:toasters@teaparty.net" <toasters@teaparty.netmailto:toasters@teaparty.net> Subject: FAS2240-4 'cluster' with 4 SSDs
Can I sanity check something?
I've got a cluster in a box - in the form of a 2240-4. Single shelf, but it's got 4 SSDs installed.
Which works as two per head.
Looking at it, I can't actually configure a hybrid aggregate, because I have to match RAID types (RAID-DP on two drives doesn't work). That's on my current code rev of 8.1.3
Upgrading to 8.2 might be a solution, because then I could RAID4 my SSDs.
But I'm wondering - what happens, given a system with no spares, one of the SSDs dies? (Or indeed, whether running with no spares is actually a good idea in the first place - I do have spares for my SAS drives, but not SSDs).
With that in mind - am I onto a bit of a loser here? And I should just be looking to replace my SSDs with some drives to match what I've got already?
Or perhaps have one head with flashpool, 3 drives + spare and one without?
Ed Morgan | Technical Consultant <115021915481801802.jpeg> T: M: 07875 628794 E: ed.morgan@ansgroup.co.ukmailto:ed.morgan@ansgroup.co.uk ANS Group London Office 18 King William Street, London, EC4N 7BP www.ans.co.ukhttp://www.ans.co.uk
<115021915481802002.png>
<115021915481801802.jpeg> Disclaimer : The information contained in this communication from Ed Morgan sent on 2015-02-19 at 15:48:18 is confidential and may be legally privileged. It is intended solely for use by toasters@teaparty.netmailto:toasters@teaparty.net and others authorised to receive it. If you are not toasters@teaparty.netmailto:toasters@teaparty.net you are hereby notified that any disclosure, copying, distribution or taking action in reliance of the contents of this information is strictly prohibited and may be unlawful. ANS Group plc Terms & Conditions apply, All Prices are subject to VAT, Expenses excluded, E&OE
ANS Group Plc - Privacy Policy - Registered Office is Synergy House, Manchester Science Park, Manchester, M15 6SY. Reg No. 3176761. (Registered in England & Wales) _______________________________________________ Toasters mailing list Toasters@teaparty.netmailto:Toasters@teaparty.net http://www.teaparty.net/mailman/listinfo/toasters
_______________________________________________ Toasters mailing list Toasters@teaparty.netmailto:Toasters@teaparty.net http://www.teaparty.net/mailman/listinfo/toasters
NetApp best practice documents (like the storage subsystem technical faq) indicate it is better to have raid_dp without spares than raid4 with a spare. It is correct that the rebuild times of SSD are rather small, but when using raid_dp you can lose two disks at the same time, raid4 only one.
Mvg, Wouter Vervloesem
Verstuurd vanaf mijn iPhone
Op 19-feb.-2015 om 18:52 heeft Jordan Slingerland <Jordan.Slingerland@independenthealth.commailto:Jordan.Slingerland@independenthealth.com> het volgende geschreven:
I think you would be okay with RAID4, 2 data disk, 1 parity and 1 spare.
Due to the size and speed of SSD, rebuilds are much faster so this is a much more resilient configuration than it would be with a similar configuration and spinning drives. In addition, with the raid group being so small having only 1 spare and 1 parity disk is not such a big deal. I certainly would not recommend no spares as the fact that you can rebuild a failed disk to a hot spare in under a few hours is an important part of the resiliency.
--JMS
From: toasters-bounces@teaparty.netmailto:toasters-bounces@teaparty.net [mailto:toasters-bounces@teaparty.net] On Behalf Of Basil Sent: Thursday, February 19, 2015 12:14 PM To: Edward Rolison Cc: toasters@teaparty.netmailto:toasters@teaparty.net Subject: Re: FAS2240-4 'cluster' with 4 SSDs
If you don't protect the SSDs and there's a failure, you'll lose data and corrupt the aggregate, I think. For flash pool, at least.
On Thu, Feb 19, 2015 at 11:38 AM, Edward Rolison <ed.rolison@gmail.commailto:ed.rolison@gmail.com> wrote: I'm not overly keen on the concept - these systems aren't particularly performance critical, so can do without. What I'm not clear on is just how weak a link a two drive/no spare RAID4 flashpool would actually be.
I mean, I don't like running without spares at all, but given I believe the flash pool is used like a cache (e.g. not a unique copy, but a replica) is that as much of a risk?
On 19 February 2015 at 16:32, Vervloesem Wouter <wouter.vervloesem@neoria.bemailto:wouter.vervloesem@neoria.be> wrote: I try not to use raid4 in FlashPools. Using raid4 may increase the amount of usable cache size, but this means your SSD raidgroup becomes the weakest link in the aggregate. I would assign all SSD's to one of the nodes and create one SSD raid_dp raigroup.
Mvg, Wouter Vervloesem
Neoria - Uptime Group Veldkant 35D B-2550 Kontich
Tel: +32 (0)3 451 23 82tel:%2B32%20%280%293%20451%2023%2082 Mailto: wouter.vervloesem@neoria.bemailto:wouter.vervloesem@neoria.be Web: http://www.neoria.be
Op 19-feb.-2015, om 16:48 heeft Ed Morgan <Ed.Morgan@ansgroup.co.ukmailto:Ed.Morgan@ansgroup.co.uk> het volgende geschreven:
I’d do 1 head with a flashpool and one without.
From: Edward Rolison <ed.rolison@gmail.commailto:ed.rolison@gmail.com> Date: Thursday, 19 February 2015 15:39 To: "toasters@teaparty.netmailto:toasters@teaparty.net" <toasters@teaparty.netmailto:toasters@teaparty.net> Subject: FAS2240-4 'cluster' with 4 SSDs
Can I sanity check something?
I've got a cluster in a box - in the form of a 2240-4. Single shelf, but it's got 4 SSDs installed.
Which works as two per head.
Looking at it, I can't actually configure a hybrid aggregate, because I have to match RAID types (RAID-DP on two drives doesn't work). That's on my current code rev of 8.1.3
Upgrading to 8.2 might be a solution, because then I could RAID4 my SSDs.
But I'm wondering - what happens, given a system with no spares, one of the SSDs dies? (Or indeed, whether running with no spares is actually a good idea in the first place - I do have spares for my SAS drives, but not SSDs).
With that in mind - am I onto a bit of a loser here? And I should just be looking to replace my SSDs with some drives to match what I've got already?
Or perhaps have one head with flashpool, 3 drives + spare and one without?
Ed Morgan | Technical Consultant <115021915481801802.jpeg> T: M: 07875 628794 E: ed.morgan@ansgroup.co.ukmailto:ed.morgan@ansgroup.co.uk ANS Group London Office 18 King William Street, London, EC4N 7BP www.ans.co.ukhttp://www.ans.co.uk
<115021915481802002.png>
<115021915481801802.jpeg> Disclaimer : The information contained in this communication from Ed Morgan sent on 2015-02-19 at 15:48:18 is confidential and may be legally privileged. It is intended solely for use by toasters@teaparty.netmailto:toasters@teaparty.net and others authorised to receive it. If you are not toasters@teaparty.netmailto:toasters@teaparty.net you are hereby notified that any disclosure, copying, distribution or taking action in reliance of the contents of this information is strictly prohibited and may be unlawful. ANS Group plc Terms & Conditions apply, All Prices are subject to VAT, Expenses excluded, E&OE
ANS Group Plc - Privacy Policy - Registered Office is Synergy House, Manchester Science Park, Manchester, M15 6SY. Reg No. 3176761. (Registered in England & Wales) _______________________________________________ Toasters mailing list Toasters@teaparty.netmailto:Toasters@teaparty.net http://www.teaparty.net/mailman/listinfo/toasters
_______________________________________________ Toasters mailing list Toasters@teaparty.netmailto:Toasters@teaparty.net http://www.teaparty.net/mailman/listinfo/toasters
_______________________________________________ Toasters mailing list Toasters@teaparty.netmailto:Toasters@teaparty.net http://www.teaparty.net/mailman/listinfo/toasters
See section 4.1 Deployment Considerations in the Flash Pool Technical Report (TR-4070). Publicly accessible here:
http://www.netapp.com/us/media/tr-4070.pdf
I had similar questions a while ago. It seems that RAID-DP for cache RAID group is the best practice however the TR goes on to call out a couple of exceptions with regard to the FAS2200 series arrays. Straight from section 4.1 of the TR:
"When using Data ONTAP 8.2 or a subsequent release, the RAID policies for the SSD RAID group and HDD RAID groups in a Flash Pool aggregate are independent. That means an SSD RAID group could be RAID 4 protected, while the HDD RAID groups in the same Flash Pool aggregate use RAID-DP protection. *Nevertheless, the added protection of RAID-DP makes it a best practice to use RAID-DP for SSD RAID groups as well.* An uncorrectable error in an SSD RAID group that is configured with RAID 4 and has experienced the failure of one SSD results in the entire Flash Pool aggregate being taken offline. It could also cause a loss of data that is cached in the write cache. Therefore, NetApp recommends using RAID-DP protection for SSD RAID groups and HDD RAID groups."
"NetApp also recommends maintaining at least one spare SSD for each node (controller) that has a Flash Pool aggregate configured on it. *However, on a FAS2200 series system that is running a Data ONTAP 8.1.x release, it is acceptable to configure the SSD RAID group in the Flash Pool aggregate with RAIDDP and to operate without a hot spare SSD.*"
"*On a FAS2200 series system that is running Data ONTAP 8.2, the recommendation is to configure the SSD RAID group with RAID 4 protection and one hot spare SSD.* With this configuration, data is protected, and an immediate and fast RAID group rebuild occurs if a SSD fails. If RAID 4 protection is chosen for an SSD RAID group in a Flash Pool aggregate on any other FAS or V-Series system, at least one hot spare SSD should be maintained for each node that has a Flash Pool aggregate configured on it."
On Thu, Feb 19, 2015 at 11:57 AM, Vervloesem Wouter < wouter.vervloesem@neoria.be> wrote:
NetApp best practice documents (like the storage subsystem technical faq) indicate it is better to have raid_dp without spares than raid4 with a spare. It is correct that the rebuild times of SSD are rather small, but when using raid_dp you can lose two disks at the same time, raid4 only one.
Mvg, Wouter Vervloesem
Verstuurd vanaf mijn iPhone
Op 19-feb.-2015 om 18:52 heeft Jordan Slingerland < Jordan.Slingerland@independenthealth.com> het volgende geschreven:
I think you would be okay with RAID4, 2 data disk, 1 parity and 1 spare.
Due to the size and speed of SSD, rebuilds are much faster so this is a much more resilient configuration than it would be with a similar configuration and spinning drives. In addition, with the raid group being so small having only 1 spare and 1 parity disk is not such a big deal. I certainly would not recommend no spares as the fact that you can rebuild a failed disk to a hot spare in under a few hours is an important part of the resiliency.
--JMS
*From:* toasters-bounces@teaparty.net [ mailto:toasters-bounces@teaparty.net toasters-bounces@teaparty.net] *On Behalf Of *Basil *Sent:* Thursday, February 19, 2015 12:14 PM *To:* Edward Rolison *Cc:* toasters@teaparty.net *Subject:* Re: FAS2240-4 'cluster' with 4 SSDs
If you don't protect the SSDs and there's a failure, you'll lose data and corrupt the aggregate, I think. For flash pool, at least.
On Thu, Feb 19, 2015 at 11:38 AM, Edward Rolison ed.rolison@gmail.com wrote:
I'm not overly keen on the concept - these systems aren't particularly performance critical, so can do without. What I'm not clear on is just how weak a link a two drive/no spare RAID4 flashpool would actually be.
I mean, I don't like running without spares at all, but given I believe the flash pool is used like a cache (e.g. not a unique copy, but a replica) is that as much of a risk?
On 19 February 2015 at 16:32, Vervloesem Wouter < wouter.vervloesem@neoria.be> wrote:
I try not to use raid4 in FlashPools. Using raid4 may increase the amount of usable cache size, but this means your SSD raidgroup becomes the weakest link in the aggregate. I would assign all SSD's to one of the nodes and create one SSD raid_dp raigroup.
Mvg, Wouter Vervloesem
Neoria - Uptime Group Veldkant 35D B-2550 Kontich
Tel: +32 (0)3 451 23 82 Mailto: wouter.vervloesem@neoria.be Web: http://www.neoria.be
Op 19-feb.-2015, om 16:48 heeft Ed Morgan Ed.Morgan@ansgroup.co.uk
het volgende geschreven:
I’d do 1 head with a flashpool and one without.
From: Edward Rolison ed.rolison@gmail.com Date: Thursday, 19 February 2015 15:39 To: "toasters@teaparty.net" toasters@teaparty.net Subject: FAS2240-4 'cluster' with 4 SSDs
Can I sanity check something?
I've got a cluster in a box - in the form of a 2240-4. Single shelf, but
it's got 4 SSDs installed.
Which works as two per head.
Looking at it, I can't actually configure a hybrid aggregate, because I
have to match RAID types (RAID-DP on two drives doesn't work). That's on my current code rev of 8.1.3
Upgrading to 8.2 might be a solution, because then I could RAID4 my SSDs.
But I'm wondering - what happens, given a system with no spares, one of
the SSDs dies? (Or indeed, whether running with no spares is actually a good idea in the first place - I do have spares for my SAS drives, but not SSDs).
With that in mind - am I onto a bit of a loser here? And I should just
be looking to replace my SSDs with some drives to match what I've got already?
Or perhaps have one head with flashpool, 3 drives + spare and one
without?
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Hot data (recently overwritten) is only stored on the SSD disks. So if you lose the SSD raidgroup of the FlashPool all the data on the aggregate is lost.
Mvg, Wouter Vervloesem
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Op 19-feb.-2015 om 18:23 heeft Basil <basilberntsen@gmail.commailto:basilberntsen@gmail.com> het volgende geschreven:
If you don't protect the SSDs and there's a failure, you'll lose data and corrupt the aggregate, I think. For flash pool, at least.
On Thu, Feb 19, 2015 at 11:38 AM, Edward Rolison <ed.rolison@gmail.commailto:ed.rolison@gmail.com> wrote: I'm not overly keen on the concept - these systems aren't particularly performance critical, so can do without. What I'm not clear on is just how weak a link a two drive/no spare RAID4 flashpool would actually be.
I mean, I don't like running without spares at all, but given I believe the flash pool is used like a cache (e.g. not a unique copy, but a replica) is that as much of a risk?
On 19 February 2015 at 16:32, Vervloesem Wouter <wouter.vervloesem@neoria.bemailto:wouter.vervloesem@neoria.be> wrote: I try not to use raid4 in FlashPools. Using raid4 may increase the amount of usable cache size, but this means your SSD raidgroup becomes the weakest link in the aggregate. I would assign all SSD's to one of the nodes and create one SSD raid_dp raigroup.
Mvg, Wouter Vervloesem
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Op 19-feb.-2015, om 16:48 heeft Ed Morgan <Ed.Morgan@ansgroup.co.ukmailto:Ed.Morgan@ansgroup.co.uk> het volgende geschreven:
I’d do 1 head with a flashpool and one without.
From: Edward Rolison <ed.rolison@gmail.commailto:ed.rolison@gmail.com> Date: Thursday, 19 February 2015 15:39 To: "toasters@teaparty.netmailto:toasters@teaparty.net" <toasters@teaparty.netmailto:toasters@teaparty.net> Subject: FAS2240-4 'cluster' with 4 SSDs
Can I sanity check something?
I've got a cluster in a box - in the form of a 2240-4. Single shelf, but it's got 4 SSDs installed.
Which works as two per head.
Looking at it, I can't actually configure a hybrid aggregate, because I have to match RAID types (RAID-DP on two drives doesn't work). That's on my current code rev of 8.1.3
Upgrading to 8.2 might be a solution, because then I could RAID4 my SSDs.
But I'm wondering - what happens, given a system with no spares, one of the SSDs dies? (Or indeed, whether running with no spares is actually a good idea in the first place - I do have spares for my SAS drives, but not SSDs).
With that in mind - am I onto a bit of a loser here? And I should just be looking to replace my SSDs with some drives to match what I've got already?
Or perhaps have one head with flashpool, 3 drives + spare and one without?
Ed Morgan | Technical Consultant <115021915481801802.jpeg> T: M: 07875 628794 E: ed.morgan@ansgroup.co.ukmailto:ed.morgan@ansgroup.co.uk ANS Group London Office 18 King William Street, London, EC4N 7BP www.ans.co.ukhttp://www.ans.co.uk
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<115021915481801802.jpeg> Disclaimer : The information contained in this communication from Ed Morgan sent on 2015-02-19 at 15:48:18 is confidential and may be legally privileged. It is intended solely for use by toasters@teaparty.netmailto:toasters@teaparty.net and others authorised to receive it. If you are not toasters@teaparty.netmailto:toasters@teaparty.net you are hereby notified that any disclosure, copying, distribution or taking action in reliance of the contents of this information is strictly prohibited and may be unlawful. ANS Group plc Terms & Conditions apply, All Prices are subject to VAT, Expenses excluded, E&OE
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Basil -
Ed Morgan -
Edward Rolison -
Jordan Slingerland -
Philbert Rupkins -
Vervloesem Wouter