topic Re: Flash Pool with a total of 4 SSD in ONTAP Discussions

Flash Pool with a total of 4 SSD

alessice — Wed, 04 Jun 2025 10:02:47 GMT

Hi,

we buy a new FAS2720 with 4 SSD and 8 HDD and 3 DS212C with 12 HDD each, for a total of 4 SSD 960GB and 44 HDD 4TB.

Now I'm configuring Flash Pool, like the old FAS2554 (4 SSD + 20 HDD) that will be migrated on the new FAS.

So I use the same command use some years ago on the 2554:

storage aggregate modify -aggregate cluster4_01_NL_SAS_1 -hybrid-enabled true

storage pool create -storage-pool StoragePool_c4_Cache1 -disk-list 1.0.0,1.0.10,1.0.1

now

storage aggregate show-spare-disks -disk-type SSD

show one disk as spare on node02 (the same as 2554).

> storage aggregate show-spare-disks -disk-type SSD Original Owner: cluster4-02 Pool0 Spare Pool Usable Physical Disk Type Class RPM Checksum Size Size Status ---------------- ------ ----------- ------ -------------- -------- -------- -------- 1.0.11 SSD solid-state - block 894.0GB 894.3GB zeroed

But when I try to add flash-pool to aggregate I have this error:

storage aggregate add cluster4_01_NL_SAS_1 -storage-pool StoragePool_c4_Cache1 -allocation-units 4 -raidtype raid4

Error: command failed: storage pool "StoragePool_c4_Cache1" does not have enough spare allocation units. Use "storage pool show-available-capacity" to get the spare allocation units assigned to node cluster4-01.

storage pool show-available-capacity Storage SyncMirror Allocation Unit Total Node Storage Pool Type Pool Unit size Count Usable Size ---------- --------------- ------- ---------- ---------- ----- ----------- cluster4-01 StoragePool_c4_Cache1 SSD Pool0 670.5GB 2 1.31TB cluster4-02 StoragePool_c4_Cache1 SSD Pool0 670.5GB 2 1.31TB 2 entries were displayed.

So, what is changed on FAS2720 and/or ONTAP 9.9.1? I remember that in the past an SSD spare can be shared from node.

Now I'm in difficulty if I cannot create my flash pool.

Thanks

Re: Flash Pool with a total of 4 SSD

TMACMD — Thu, 31 Mar 2022 17:54:56 GMT

By default, two allocation units are auto-assigned to each node. That is why when you try to specify 4 units, it is failing. It would probably work with 2 units

If you >>really<< want all four units to be part of the same aggregate, you will need to reassign the other two units:

STORAGE POOL REASSIGN

Re: Flash Pool with a total of 4 SSD

alessice — Thu, 31 Mar 2022 18:48:45 GMT

Ok, probably understand what is wrong, on my documentation I write "-allocation-units 4" but was "2", because I need to add flash pool to 2 aggregate and if reassign a total of 4 AU to only one node is impossible to do this.

Here is the status of flash-pool on current FAS 2554 that I want replicated on FAS 2720:

cluster2::> storage pool show-disks -storage-pool ClusterCache Storage Pool Name: ClusterCache Disk Disk Type Usable Size Total Size -------- ------- ----------- ----------- 1.0.0 SSD 372.4GB 372.6GB 1.0.1 SSD 372.4GB 372.6GB 1.0.2 SSD 372.4GB 372.6GB 3 entries were displayed. cluster2::> storage pool show-disks -storage-pool ClusterCache -instance Name of Storage Pool: ClusterCache Name of the disk: 1.0.0 Disk Type: SSD Disk Usable Size: 372.4GB Total Size: 372.6GB List of Nodes: cluster2-node01, cluster2-node02 Name of Storage Pool: ClusterCache Name of the disk: 1.0.1 Disk Type: SSD Disk Usable Size: 372.4GB Total Size: 372.6GB List of Nodes: cluster2-node01, cluster2-node02 Name of Storage Pool: ClusterCache Name of the disk: 1.0.2 Disk Type: SSD Disk Usable Size: 372.4GB Total Size: 372.6GB List of Nodes: cluster2-node01, cluster2-node02 3 entries were displayed. cluster2::> storage pool show-disks -storage-pool ClusterCache Storage Pool Name: ClusterCache Disk Disk Type Usable Size Total Size -------- ------- ----------- ----------- 1.0.0 SSD 372.4GB 372.6GB 1.0.1 SSD 372.4GB 372.6GB 1.0.2 SSD 372.4GB 372.6GB 3 entries were displayed. cluster2::> storage aggregate show-spare-disks -disk-type SSD Original Owner: cluster2-node01 Pool0 Spare Pool Usable Physical Disk Type Class RPM Checksum Size Size Status ---------------- ------ ----------- ------ -------------- -------- -------- -------- 1.0.3 SSD solid-state - block 372.4GB 372.6GB zeroed cluster2::> storage pool show -storage-pool ClusterCache -instance Storage Pool Name: ClusterCache UUID of Storage Pool: 3a072807-eec0-11e6-bd65-00a098c6ed93 Nodes Sharing the Storage Pool: cluster2-node02, cluster2-node01 Number of Disks in Storage Pool: 3 Allocation Unit Size: 279.2GB Allocation Unit Data Size for RAID4: 186.2GB Allocation Unit Data Size for RAID-DP: 93.08GB Allocation Unit Data Size for RAID-TEC: - Storage Type: SSD Storage Pool Usable Size: 0B Storage Pool Total Size: 1.09TB Is Pool Healthy?: true State of the Storage Pool: normal Reason for Storage Pool Being Unhealthy: - Job ID of the Currently Running Operation: - cluster2::> storage pool show-aggregate -storage-pool ClusterCache -instance Name of Storage Pool: ClusterCache Aggregate: sata_data_1 Capacity: 558.5GB Number of AU's Assigned to This Aggregate: 2 Original Owner Name: cluster2-node01 Node: cluster2-node01 Name of Storage Pool: ClusterCache Aggregate: sata_data_2 Capacity: 558.5GB Number of AU's Assigned to This Aggregate: 2 Original Owner Name: cluster2-node02 Node: cluster2-node02 2 entries were displayed.

So, I have two nodes, two aggregate set as hybrid, 4 SSD 960GB:

storage aggregate modify -aggregate cluster4_01_NL_SAS_1 -hybrid-enabled true storage aggregate modify -aggregate cluster4_02_NL_SAS_1 -hybrid-enabled true

I will create a storage pool with 3 SSD, so one remains as spare, and assign 2 AU per aggregate with raid4 type:

storage aggregate add cluster4_01_NL_SAS_1 -storage-pool StoragePool_c4_Cache1 -allocation-units 2 -raidtype raid4 storage aggregate add cluster4_02_NL_SAS_1 -storage-pool StoragePool_c4_Cache1 -allocation-units 2 -raidtype raid4

I prefer raid4 instead of Raid-DP in order to have more space on flash-pool.

All should works fine, correct? Any suggestions?

Thanks

Re: Flash Pool with a total of 4 SSD

TMACMD — Thu, 31 Mar 2022 19:43:27 GMT

You are looking at two methods for FlashPool. The old method used WHOLE SSDs. The NEW method uses PARTITIONED SSDs.

All 4 SSDs should be modified to be "owned" by the same node.

Create the storage pool with 3 x SSDs.

Modify the aggr to be hybrid enabled

Finally "add-disks" to each of your two AGGRs. Like you mention, use a storage-pool and specify raid4 to maximize usage.

You can only do one at a time. You need to wait for the first to finish before doing the second aggr. It will complain and not run if it is still adding-cache.

Re: Flash Pool with a total of 4 SSD

alessice — Fri, 01 Apr 2022 13:32:07 GMT

Ok, after set as 2 the number of AU per aggregate I have add successfully the flash-pool to the two aggregates.

Now ONTAP but also AIQ warning me about a low number of SSD spare on node01, since of 4 SSD there is only one spare assigned to node02:

cluster4::> storage pool show-disks Storage Pool Name: StoragePool_c4_Cache1 Disk Disk Type Usable Size Total Size -------- ------- ----------- ----------- 1.0.0 SSD 894.0GB 894.3GB 1.0.1 SSD 894.0GB 894.3GB 1.0.10 SSD 894.0GB 894.3GB 3 entries were displayed. cluster4::> storage aggregate show-spare-disks -disk-type SSD Original Owner: cluster4-02 Pool0 Spare Pool Usable Physical Disk Type Class RPM Checksum Size Size Status ---------------- ------ ----------- ------ -------------- -------- -------- -------- 1.0.11 SSD solid-state - block 894.0GB 894.3GB zeroed

Should I change the assignment of this SSD or in case of one SSD fail, indipendentment from node01 or node02, this spare will use?

I remember that in the past only one SSD for spare, in Flash Pool, is safe for all nodes in HA.

Thanks