From: Michael Tokarev <mjt@tls.msk.ru>
To: Justin Piszcz <jpiszcz@lucidpixels.com>
Cc: dean gaudet <dean@arctic.org>, Bill Davidsen <davidsen@tmr.com>,
linux-raid@vger.kernel.org, Alan Piszcz <ap@solarrain.com>
Subject: Re: Linux RAID Partition Offset 63 cylinders / 30% performance hit?
Date: Sun, 30 Dec 2007 04:33:09 +0300 [thread overview]
Message-ID: <4776F555.7040607@msgid.tls.msk.ru> (raw)
In-Reply-To: <Pine.LNX.4.64.0712291234230.31479@p34.internal.lan>
Justin Piszcz wrote:
[]
> Good to know/have it confirmed by someone else, the alignment does not
> matter with Linux/SW RAID.
Alignment matters when one partitions Linux/SW raid array.
If the inside partitions will not be aligned on a stripe
boundary, esp. in the worst case when the filesystem blocks
cross the stripe boundary (wonder if it's ever possible...
and I think it is, if a partition starts at some odd 512
bytes boundary, and filesystem block size is 4Kb, there's
just no chance for an inside filesystem to do full-stripe
writes, ever, so (modulo stripe cache size) all writes will
go read-modify-write or similar way.
And that's what the original article is about, by the way.
It just happens that hardware raid array is more often split
into partitions (using native tools) than linux software raid
arrays.
And that's what has been pointed out in this thread, as well... ;)
/mjt
prev parent reply other threads:[~2007-12-30 1:33 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-12-19 14:50 Linux RAID Partition Offset 63 cylinders / 30% performance hit? Justin Piszcz
2007-12-19 15:01 ` Mattias Wadenstein
2007-12-19 15:04 ` Justin Piszcz
2007-12-19 15:06 ` Jon Nelson
2007-12-19 15:31 ` Justin Piszcz
2007-12-20 10:37 ` Gabor Gombas
2007-12-19 17:40 ` Bill Davidsen
2007-12-19 17:37 ` Jon Nelson
2007-12-19 17:37 ` Jon Nelson
2007-12-19 17:55 ` Justin Piszcz
2007-12-19 19:18 ` Bill Davidsen
2007-12-19 19:44 ` Justin Piszcz
2007-12-19 21:31 ` Justin Piszcz
2007-12-20 15:18 ` Bill Davidsen
2007-12-20 15:00 ` Justin Piszcz
2007-12-20 10:24 ` Gabor Gombas
2007-12-20 10:33 ` Gabor Gombas
2007-12-19 21:44 ` Michal Soltys
2007-12-19 22:12 ` Jon Nelson
2007-12-20 13:01 ` Michal Soltys
2007-12-19 21:59 ` Robin Hill
2007-12-19 22:03 ` Justin Piszcz
2007-12-25 19:06 ` Bill Davidsen
2007-12-29 17:22 ` dean gaudet
2007-12-29 17:34 ` Justin Piszcz
2007-12-30 1:33 ` Michael Tokarev [this message]
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