From: John Robinson <john.robinson@anonymous.org.uk>
To: Neil Brown <neilb@suse.de>
Cc: James Bottomley <James.Bottomley@HansenPartnership.com>,
Greg Freemyer <greg.freemyer@norcrossgroup.com>,
Ric Wheeler <rwheeler@redhat.com>,
linux-raid <linux-raid@vger.kernel.org>,
Dongjun Shin <djshin90@gmail.com>,
IDE/ATA development list <linux-ide@vger.kernel.org>
Subject: Re: SSD data reliable vs. unreliable [Was: Re: Data Recovery from SSDs - Impact of trim?]
Date: Tue, 27 Jan 2009 10:49:08 +0000 [thread overview]
Message-ID: <497EE6A4.7030406@anonymous.org.uk> (raw)
In-Reply-To: <18814.39074.194781.490676@notabene.brown>
On 27/01/2009 05:16, Neil Brown wrote:
[...]
> Probably the only practical data structure for this would be a bitmap
> similar to the current write-intent bitmap.
>
> Is it really worth supporting this in raid5? Are the sorts of
> devices that will benefit from 'discard' requests likely to be used
> inside an md/raid5 array I wonder....
Assuming I've understood correctly, this usage map sounds to me like a
useful thing to have for all RAIDs. When building the array in the first
place, the initial sync is just writing a usage map saying it's all
empty. Filesystem writes and discards update it appropriately. Then when
we get failing sectors reported via e.g. SMART or a scrub operation we
know whether they're on used or unused areas so whether it's worth
attempting recovery.
Cheers,
John.
next prev parent reply other threads:[~2009-01-27 10:49 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-01-22 23:53 SSD data reliable vs. unreliable [Was: Re: Data Recovery from SSDs - Impact of trim?] Greg Freemyer
2009-01-23 20:40 ` Ric Wheeler
2009-01-23 22:24 ` James Bottomley
2009-01-23 23:26 ` Greg Freemyer
2009-01-23 23:35 ` Ric Wheeler
[not found] ` <7fce22690901260659u30ffd634m3fb7f75102141ee9@mail.gmail.com>
2009-01-26 16:22 ` Ric Wheeler
2009-01-26 17:34 ` Greg Freemyer
2009-01-26 17:46 ` Ric Wheeler
2009-01-26 17:47 ` James Bottomley
2009-01-27 5:16 ` Neil Brown
2009-01-27 10:49 ` John Robinson [this message]
2009-01-28 20:11 ` Bill Davidsen
[not found] ` <7fce22690901281556h67fb353dp879f88e6c2a76eaf@mail.gmail.com>
2009-01-29 1:49 ` John Robinson
2009-01-27 11:23 ` Ric Wheeler
2009-01-28 20:28 ` Bill Davidsen
2009-01-27 14:48 ` James Bottomley
2009-01-27 14:54 ` Ric Wheeler
2009-01-26 17:51 ` Mark Lord
2009-01-26 18:09 ` Greg Freemyer
2009-01-26 18:21 ` Mark Lord
2009-01-29 14:07 ` Dongjun Shin
2009-01-29 15:46 ` Mark Lord
2009-01-29 16:27 ` Greg Freemyer
2009-01-30 15:43 ` Bill Davidsen
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