From mboxrd@z Thu Jan  1 00:00:00 1970
From: John Robinson <john.robinson@anonymous.org.uk>
Subject: Re: SSD data reliable vs. unreliable [Was: Re: Data Recovery from
 	SSDs - Impact of trim?]
Date: Thu, 29 Jan 2009 01:49:55 +0000
Message-ID: <49810B43.20108@anonymous.org.uk>
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To: Greg Freemyer <greg.freemyer@norcrossgroup.com>
Cc: Bill Davidsen <davidsen@tmr.com>, Neil Brown <neilb@suse.de>, James Bottomley <James.Bottomley@hansenpartnership.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>

On 28/01/2009 23:56, Greg Freemyer wrote:
> Once discard calls get into linux file systems mdraid and/or device
> mapper could implement linux's own thin provisioning implementation.
> Even with traditional disks that don't support unmap.  I gather that
> is what the EMCs of the world will be doing in their platforms.
> 
> http://en.wikipedia.org/wiki/Thin_provisioning

Sounds more like a device mapper or LVM thing (than md/RAID) to me, but 
I'd definitely agree that this would be another great reason for block 
devices to implement map/unmap.

And I wonder if there's room for another dm/md device type which just 
implements these usage maps over traditional devices which don't support 
unmap (much as I was wondering a few weeks back about a soft DIF 
implementation over e.g. SATA devices). Darn it, I might just have to 
dig out my school books on C; it's a while since I offered a kernel patch.

Cheers,

John.