ZFS UNMAP performance

[Danny Schales]

On 3/11/2014 5:31 PM, Eric van Gyzen wrote:
>> Replying to myself...I note that the system is reporting that TRIM is
>> being used.  Is this normal for non-SSD systems?  There *is* SSD in the
>> system, but I'm pretty sure the system can't tell it's SSD (it's hidden
>> behind a Dell PERC card).  The number of trim.successes is roughly
>> equivalent to the number of deletes reported by gstat for the ISCSI LUN
>> devices.  Should the system be using TRIM for ISCSI LUNs?
> Sure, if the LUN (i.e. the storage controller) reports that it supports
> TRIM/UNMAP.  Note that this is completely unrelated to the type of disks
> that provide the LUN's backing store.
>
>> kstat.zfs.misc.zio_trim.bytes: 232845656064
>> kstat.zfs.misc.zio_trim.success: 30810983
>> kstat.zfs.misc.zio_trim.unsupported: 809
>> kstat.zfs.misc.zio_trim.failed: 0
>>
>> Danny
>>
>

Are there any risks to turning off TRIM to see if the performance
improves (other than the loss of space recovery)?

Danny

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