From: Neil Brown <neilb@suse.de>
To: Jon Nelson <jnelson-linux-raid@jamponi.net>
Cc: Daniel Korstad <dan@korstad.net>, linux-raid@vger.kernel.org
Subject: RE: RAID 6 grow problem
Date: Thu, 7 Jun 2007 14:44:04 +1000 [thread overview]
Message-ID: <18023.36116.726823.425259@notabene.brown> (raw)
In-Reply-To: message from Jon Nelson on Wednesday June 6
On Wednesday June 6, jnelson-linux-raid@jamponi.net wrote:
>
> A question posed by a friend is this: assuming 64K blocks, if I read a
> single stripe from a raid (128K, right?) then two drives will be used
> (say, drive A and drive B). If I want the "next" 128K then which drives
> are most likely to be used? Drive A will now have the parity block in
> it's "next" block for head position, but drive B has the next data
> block. Nobody knows where drive C is. Does raid5 use an algorithm
> similar to raid1 in that it chooses the 2 drives whose heads are closest
> or does it utilize some other algorithm?
No. When it wants data, it just reads the data. It doesn't try to be
clever an read the parity block and calculate the data (unless the
data block doesn't exist of course).
NeilBrown
next prev parent reply other threads:[~2007-06-07 4:44 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-06-06 15:06 RAID 6 grow problem Daniel Korstad
2007-06-06 15:38 ` Jon Nelson
2007-06-07 4:44 ` Neil Brown [this message]
[not found] <Pine.LNX.4.64.0706021232040.13184@p34.internal.lan>
2007-06-02 21:26 ` Iain Rauch
2007-06-02 21:31 ` Justin Piszcz
2007-06-02 21:33 ` Justin Piszcz
2007-06-02 21:38 ` Neil Brown
2007-06-02 21:55 ` Iain Rauch
2007-06-02 22:07 ` Neil Brown
2007-06-02 22:35 ` Iain Rauch
2007-06-03 23:33 ` Daniel Korstad
2007-06-04 20:29 ` Bill Davidsen
2007-06-05 17:08 ` Iain Rauch
2007-06-05 19:21 ` Daniel Korstad
2007-06-05 21:26 ` Jon Nelson
2007-06-06 0:46 ` Neil Brown
2007-06-10 19:18 ` Iain Rauch
2007-06-10 20:17 ` Justin Piszcz
-- strict thread matches above, loose matches on Subject: below --
2007-06-02 15:30 Iain Rauch
2007-06-02 16:19 ` Justin Piszcz
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