From: "Martin K. Petersen" <martin.petersen@oracle.com>
To: Dan Williams <dan.j.williams@gmail.com>
Cc: "Martin K. Petersen" <martin.petersen@oracle.com>,
jens.axboe@oracle.com, neilb@suse.de,
linux-kernel@vger.kernel.org, linux-raid@vger.kernel.org
Subject: Re: [PATCH] md: Add support for data integrity to MD
Date: Sat, 20 Sep 2008 22:01:29 -0400 [thread overview]
Message-ID: <yq1ljxmmf46.fsf@sermon.lab.mkp.net> (raw)
In-Reply-To: <e9c3a7c20809201726v78f9a00gb9a168f7f9c19044@mail.gmail.com> (Dan Williams's message of "Sat\, 20 Sep 2008 17\:26\:40 -0700")
>>>>> "Dan" == Dan Williams <dan.j.williams@gmail.com> writes:
>> + /* Data integrity passthrough not supported on RAID 4, 5 and 6 */
>> + if (pers->level >= 4 && pers->level <= 6) + return 0;
Dan> Do you have a reference to the issues in supporting this?
Not really.
The protection information is an extra 8-bytes of stuff per sector.
But it comes down in a different buffer. To do R-M-W effectively
we'll have to maintain a separate protection information stripe cache.
And we'll have to generate DIF checksums and reference tags for the
parity sectors going out.
Quite frankly it's a lot of ick and I haven't completely wrapped my
head around it yet.
--
Martin K. Petersen Oracle Linux Engineering
next prev parent reply other threads:[~2008-09-21 2:01 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-09-21 0:18 [PATCH] md: Add support for data integrity to MD Martin K. Petersen
2008-09-21 0:26 ` Dan Williams
2008-09-21 2:01 ` Martin K. Petersen [this message]
2008-09-21 0:28 ` Stable versions of mdadm berk walker
2008-09-21 1:07 ` Bill Davidsen
2008-09-21 1:24 ` berk walker
2008-09-24 2:46 ` [PATCH] md: Add support for data integrity to MD Neil Brown
2008-09-29 14:51 ` Martin K. Petersen
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