From: Yinan Liu <yinan@ele.uri.edu>
To: linux-raid@vger.kernel.org
Subject: RAID-5 Parity calculation
Date: Thu, 14 Oct 2004 14:31:02 -0400 [thread overview]
Message-ID: <1097778662.2926.9.camel@localhost.localdomain> (raw)
Hi, I am a new guy for a Linux programming. I got a question for a
software RAID-5 parity calculation.
If we suppose for data block D1, D2, D3, D4 with a parity block P, When
some data block is changed, P will be changed. I am not so clear how
does Linux md handle the parity re calculating, when data changed .
Suppose there will be three cases,
1. sequential write, is that get new P' directly with new data D1', D2',
D3' and D4' or need read D1-4 out from disk doing the normal operation.
2. if we changed there blocks, D1',D2' and D3', does md read D1, D2, D3
out to rebuild P or just read D4 out from disk and rebuild P with D1',
D2', D3' and D4.
3. is the simple case, just change one block.
Thanks a lot, if some can help me get understand it.
next reply other threads:[~2004-10-14 18:31 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-10-14 18:31 Yinan Liu [this message]
2004-10-14 21:39 ` RAID-5 Parity calculation Guy
2004-10-15 0:57 ` Neil Brown
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