If one of SPS fails, that is the only time when you can enanle cache manually. In all other cases , you can't enable it.

Please also see Release Notes for the FLARE Operating Environment, available on Powerlink - the "Environment and system requirements" segment in current Notes (R28 for CX4-series, or R26 for most prior arrays) provide more detail beyond what has been outlined above by bishtsudhir.

In arrays before CX4-series; the array will automatically disable Write Cache if/when it becomes a single hardware fault away from shutting down; this cannot be over-ridden; with the exception of the Vault drives (first 5 drives in Bus 0 Enclosure 0), which is settable via Navisphere (the default setting is to disable Write Cache any time a single Vault drive fails).

The CX4-series arrays provide enhanced Write Cache availability; they can maintain Write Cache being enabled except during events such as dual loss of AC power or overtemperature conditions.

Regards,
DGM

Any specific reason that i will be able to enable cache only when the SPS fails.

And also for other cases, is it that the clariion won't allow me to enable cache, or are you saying I should not enable for a reason?

The HA Cache Vault checkbox in storage system properties allows vault operation to continue, even if a vault disk has failed. Write cache will not be disabled if a single vault drive fails

Thanks bishtsudhir and DGM!