From: NeilBrown <neilb@suse.de>
To: Justin Piszcz <jpiszcz@lucidpixels.com>
Cc: linux-kernel@vger.kernel.org, linux-raid@vger.kernel.org
Subject: Re: 3.10: discard/trim support on md-raid1?
Date: Tue, 16 Jul 2013 17:15:27 +1000 [thread overview]
Message-ID: <20130716171527.7c6cb722@notabene.brown> (raw)
In-Reply-To: <001701ce7fb4$889bdd40$99d397c0$@lucidpixels.com>
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On Sat, 13 Jul 2013 06:34:19 -0400 "Justin Piszcz" <jpiszcz@lucidpixels.com>
wrote:
> Hello,
>
> Running 3.10 and I see the following for an md-raid1 of two SSDs:
>
> Checking /sys/block/md1/queue:
> add_random: 0
> discard_granularity: 512
> discard_max_bytes: 2147450880
> discard_zeroes_data: 0
> hw_sector_size: 512
> iostats: 0
> logical_block_size: 512
> max_hw_sectors_kb: 32767
> max_integrity_segments: 0
> max_sectors_kb: 512
> max_segment_size: 65536
> max_segments: 168
> minimum_io_size: 512
> nomerges: 0
> nr_requests: 128
> optimal_io_size: 0
> physical_block_size: 512
> read_ahead_kb: 8192
> rotational: 1
> rq_affinity: 0
> scheduler: none
> write_same_max_bytes: 0
>
> What should be seen:
> rotational: 0
What has "rotational" got to do with "supports discard"?
There may be some correlation, but it isn't causal.
> And possibly:
> discard_zeroes_data: 1
This should be set as the 'or' of the same value from component devices. And
does not enable or disable the use of discard.
I don't think that "does this device support discard" appears in sysfs.
I believe trim does work on md/raid1 if the underlying devices all support it.
NeilBrown
>
> Can anyone confirm if there is a workaround to allow TRIM when using
> md-raid1?
>
> Some related discussion here:
> http://us.generation-nt.com/answer/md-rotational-attribute-help-206571222.ht
> ml
> http://www.progtown.com/topic343938-ssd-strange-itself-conducts.html
>
>
> Justin.
>
>
> --
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next prev parent reply other threads:[~2013-07-16 7:15 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-07-13 10:34 3.10: discard/trim support on md-raid1? Justin Piszcz
2013-07-13 10:47 ` Brad Campbell
2013-07-16 7:15 ` NeilBrown [this message]
2013-07-16 8:09 ` Justin Piszcz
2013-07-16 8:22 ` David Lang
2013-07-16 20:44 ` CoolCold
2013-07-17 1:48 ` NeilBrown
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