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Date:      Tue, 11 Mar 2014 19:28:16 -0500
From:      Danny Schales <dan@latech.edu>
To:        freebsd-stable@freebsd.org
Subject:   Re: ZFS UNMAP performance
Message-ID:  <531FAA20.7080407@latech.edu>
In-Reply-To: <531F8EAA.1020107@vangyzen.net>
References:  <531F2BA0.6000105@LaTech.edu> <CAFHbX1JghVaQ3xM2OZ6jpWOs6tn=Z8epd8Om3NW_CDnZHPSdng@mail.gmail.com> <531F3503.8090403@LaTech.edu> <531F767C.3040105@LaTech.edu> <531F8EAA.1020107@vangyzen.net>

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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 th=
e
>> system, but I'm pretty sure the system can't tell it's SSD (it's hidde=
n
>> behind a Dell PERC card).  The number of trim.successes is roughly
>> equivalent to the number of deletes reported by gstat for the ISCSI LU=
N
>> 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 disk=
s
> 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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