AFF, NVMe, and EF-Series Discussions

SIZING 24 SSDs for 2 FLASH POOLS

heightsnj

I have 1 shelf SSD X24. planning on creating 2 flash pools for 1 agg on each node within a pair, RAID-DP

Should I do: 9 data, 2 dp, 1 spare, or 8 data, 2dp, 2 spares for each pool? can data disks be odd number?

 

Also, among 24 SSDs, 7 is owned by one node, 17 is owned by the other. Should I split the ownership by half and half before creating the pool or does that matter?

 

Thanks for sharing!

7 REPLIES 7

rwelshman

You have to split the ownership if you want 12 disks used for each node.

 

You can have an odd number of disks in a raid group, that's no problem. Whether you have 1 or 2 spares is a personal choice. One spare would give you more usable capacity. If you know you could get a replacement disk quickly - then 1 spare should be fine. If it might take awhile to get a replacement on site, you may want to have more than 1.

heightsnj

Thanks!

 

A follow-up.

 

When one failed, can SSD spare on the other node substitue the failed one?

mikkisse

Hello!

 

Also, if you  run on DataONTAP 8.3 you can look at storage pool technology. 

https://library.netapp.com/ecmdocs/ECMP1636022/html/GUID-8284CB30-5BC5-4D10-B0AA-AA8F8DAA752E.html

heightsnj

Thanks!

 

Could somebody please let me know if a disk failed on one node, and a spare disk on the other node could be selected for rebuilt? both nodes in the same HA.

mikkisse

For a disk to be used as a hot spare for another disk, it must conform to the following criteria: 

• It must be either an exact match for the disk it is replacing or an appropriate alternative.

• If SyncMirror is in use, the spare must be in the same pool as the disk it is replacing.

• The spare must be owned by the same system as the disk it is replacing.

 

heightsnj

What is your suggestion to use either Storage Pool or Dedicated SSD aggr for Flash Pool?

 

 

 

Thanks!

 

J-L-B

I would split the shelf - odd #'s to one controller and even #'s to the other controller.  Since the SSDs are so expensive, we chose to go with #disks+2DP with 1 spare.  The rebuild times are extremely fast on the SSD raidgroup.  You would essentially have to lose 3 disks within 4 hours if you only have 4 hour support.  Never had a SSD fail in my experience.

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