From: Zdenek Kaspar <zkaspar82@gmail.com>
To: linux-raid@vger.kernel.org
Subject: Re: RAID5 alignment issues with 4K/AF drives (WD green ones)
Date: Fri, 30 Dec 2011 03:00:34 +0100 [thread overview]
Message-ID: <4EFD1B42.3040009@gmail.com> (raw)
In-Reply-To: <A0933627-0D84-496C-B7B7-4FE265C2A212@gmail.com>
Dne 30.12.2011 0:28, Michele Codutti napsal(a):
> Hi all, I'm writing to this mailing list because I cannot figure out why I had some performance issues with my three WD20EARS (2TB Western Digital "Green" 4K/AF drive).
> These drives has a (sequential) write throughput around 100MB/s. When I combine them in a RAID0 configuration the throughput is around 300 MB/s and in a RAID1 configuration they preserve a single drive performance of 100MB/s.
> When I combine all three drives in a RAID5 configuration the (individual) performance falls around 40MB/s.
> I get the same performance level when I do individual misaligned writes (ex: dd if=/dev/zero bs=6K of=/dev/sda).
> The drives are not partitioned. I'm using the default chunk size (512K) and the default metadata superblock version (1.2).
> I had not formatted the RAID or any single drive during my test i had directly used the raw devices.
> I'm using a 11.10 ubuntu with 3.0.0 linux kernel and 3.1.4 mdadm.
> The hardware is a HP microserver.
>
> Could you give me some advice?
> Thanks in advance.
>
> Michele--
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There must be some misalignment somewhere :( Do all drives really report
as 4K to the OS - physical_block_size, logical_block_size under
/sys/block/sdX/queue/ ??
NB: how does it perform with partitions starting at sector 2048 (check
all disks with fdisk -lu /dev/sdX).
HTH, Z.
next prev parent reply other threads:[~2011-12-30 2:00 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-12-29 23:28 RAID5 alignment issues with 4K/AF drives (WD green ones) Michele Codutti
2011-12-30 2:00 ` Zdenek Kaspar [this message]
2011-12-30 4:48 ` Marcus Sorensen
2011-12-30 4:52 ` Mikael Abrahamsson
2011-12-30 5:45 ` Marcus Sorensen
2011-12-30 6:09 ` Marcus Sorensen
2011-12-31 3:12 ` Mikael Abrahamsson
2011-12-30 6:24 ` Brad Campbell
2011-12-30 21:04 ` Michele Codutti
2011-12-30 23:17 ` Zdenek Kaspar
2011-12-31 22:20 ` Marcus Sorensen
2011-12-31 15:53 ` John Robinson
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