Dell EMC PowerVault MD 34XX/38XX Series Storage Arrays Administrator's Guide

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SSD cache restrictions

The following restrictions apply to using SSD cache feature:

SSD cache is not supported on Snapshot Virtual Disks.
If you import or export base virtual disks that are SSD cache enabled or disabled, the cached data is not imported or exported.
Maximum usable SSD cache capacity on a storage array is dependent on the RAID controller module’s primary cache capacity.
You cannot remove the last physical disk in an SSD cache without first deleting the SSD cache.
Only one SSD cache is supported per storage array.
If all the SSDs in the SSD cache are data assurance-capable and the data assurance (DA) feature is enabled, DA is automatically enabled for the SSD cache and cannot be disabled.
You cannot add non-DA capable SSDs to a DA-enabled SSD cache.