From: John Robinson <john.robinson@anonymous.org.uk>
To: "Mathias Burén" <mathias.buren@gmail.com>
Cc: linux-raid@vger.kernel.org
Subject: Re: mdadm / RAID, a few questions
Date: Fri, 29 Oct 2010 21:22:13 +0100 [thread overview]
Message-ID: <4CCB2CF5.9010402@anonymous.org.uk> (raw)
In-Reply-To: <AANLkTi=QRfQhNy5jDdtq2FsjENZk-ihNas=D4QrS2XMd@mail.gmail.com>
On 29/10/2010 15:18, Mathias Burén wrote:
> Hi,
>
> I've a few questions in relation to mdadm and performance. System
> details follow below:
>
> Intel Atom 330 @ 1.6Ghz (dualcore, HT), 4GB RAM
[...]
> Question 1: I saw that in Linux 2.6.36 (perhaps earlier versions as
> well) you have the kernel config option CONFIG_MULTICORE_RAID456. I
> tried enabling it, booted to 2.6.36 from 2.6.35, and rebuilding of the
> array continued where it left off before reboot. However, the
> performance was abysmal.. around 16MB/s compared to 70MB/s without the
> option turned on. Is this a bug, or is it because the Atom has no
> grunt to speak of?
No, the performance of MULTICORE_RAID456 is abysmal on any CPU. It's an
experimental implementation that doesn't work terribly well. If you're
interested in developing, by all means help, but if not, turn it off.
> Question 2: The array is now recovering since I've grown it to 6 from 4 devices:
> $ cat /proc/mdstat
> Personalities : [raid6] [raid5] [raid4]
> md0 : active raid5 sdf1[0] sde1[5] sdg1[6] sdc1[3] sdd1[4] sdb1[1]
> 5851054080 blocks super 1.2 level 5, 128k chunk, algorithm 2
> [6/6] [UUUUUU]
> [===========>.........] reshape = 57.7% (1126387328/1950351360)
> finish=718.0min speed=19125K/sec
>
> unused devices:<none>
>
> Is there a way to speed it up? /proc/sys/dev/raid/speed_limit_min is
> 100000 (100k), /proc/sys/dev/raid/speed_limit_max is 1000000 (1000k).
No, that's probably about right on something as weak as an Atom. Let it run.
> Question 3: Before I created this RAID5 array I did a quick RAID0 test
> array just for fun, using 2 full devices (not partitions). Now I have
> this:
[...]
Sorry, I don't know the answer to this. I suspect it's to do with
superblock versions, but I don't know - I'm sorry that's not helpful.
Cheers,
John.
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next prev parent reply other threads:[~2010-10-29 20:22 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-10-29 14:18 mdadm / RAID, a few questions Mathias Burén
2010-10-29 20:22 ` John Robinson [this message]
2010-10-29 20:35 ` Mathias Burén
2010-10-29 20:44 ` Neil Brown
2010-11-04 20:02 ` Mathias Burén
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