You create a Flash Pool local tier (aggregate) by enabling the feature on an existing local tier composed of HDD RAID groups, and then adding one or more SSD RAID groups to that local tier. This results in two sets of RAID groups for that local tier: SSD RAID groups (the SSD cache) and HDD RAID groups.

About this task

After you add an SSD cache to an local tier to create a Flash Pool local tier, you cannot remove the SSD cache to convert the local tier back to its original configuration.

By default, the RAID level of the SSD cache is the same as the RAID level of the HDD RAID groups. You can override this default selection by specifying the “raidtype” option when you add the first SSD RAID groups.

Before you begin

You must have identified a valid local tier composed of HDDs to convert to a Flash Pool local tier.
You must have determined write-caching eligibility of the volumes associated with the local tier, and completed any required steps to resolve eligibility issues.
You must have determined the SSDs you will be adding, and these SSDs must be owned by the node on which you are creating the Flash Pool local tier.
You must have determined the checksum types of both the SSDs you are adding and the HDDs already in the local tier.
You must have determined the number of SSDs you are adding and the optimal RAID group size for the SSD RAID groups.

Using fewer RAID groups in the SSD cache reduces the number of parity disks required, but larger RAID groups require RAID-DP.
You must have determined the RAID level you want to use for the SSD cache.
You must have determined the maximum cache size for your system and determined that adding SSD cache to your local tier will not cause you to exceed it.
You must have familiarized yourself with the configuration requirements for Flash Pool local tiers.

Steps

You can create a FlashPool aggregate using ONTAP System Manager or the ONTAP CLI.

ONTAP System Manager

Beginning with ONTAP 9.12.1, you can use ONTAP System Manager to create a Flash Pool local tier using physical SSDs.

Steps

Select Storage > Tiers then select an existing local HDD storage tier.
Select then Add Flash Pool Cache.
Select Use dedicated SSDs as cache.
Select a disk type and the number of disks.
Choose a RAID type.
Select Save.
Locate the storage tier then select .
Select More Details. Verify that Flash Pool shows as Enabled.

CLI

Steps

Mark the local tier (aggregate) as eligible to become a Flash Pool aggregate:

storage aggregate modify -aggregate aggr_name -hybrid-enabled true

If this step does not succeed, determine write-caching eligibility for the target aggregate.
Add the SSDs to the aggregate by using the storage aggregate add command.
- You can specify the SSDs by ID or by using the diskcount and disktype parameters.
- If the HDDs and the SSDs do not have the same checksum type, or if the aggregate is a mixed-checksum aggregate, then you must use the checksumstyle parameter to specify the checksum type of the disks you are adding to the aggregate.
- You can specify a different RAID type for the SSD cache by using the raidtype parameter.
- If you want the cache RAID group size to be different from the default for the RAID type you are using, you should change it now, by using the -cache-raid-group-size parameter.