From: Roberto Spadim <roberto@spadim.com.br>
To: Liam Kurmos <quantum.leaf@gmail.com>
Cc: NeilBrown <neilb@suse.de>,
Brad Campbell <lists2009@fnarfbargle.com>,
Drew <drew.kay@gmail.com>,
linux-raid@vger.kernel.org
Subject: Re: mdadm raid1 read performance
Date: Wed, 4 May 2011 21:25:55 -0300 [thread overview]
Message-ID: <BANLkTi=2WCfoXTtyRzpBN06ph6HCsy_ShQ@mail.gmail.com> (raw)
In-Reply-To: <BANLkTimNxTnf2xW8hbEWK2iA6axqjnjT+A@mail.gmail.com>
raid10,f2 is a stripe configuration and mirror too, think about it like this:
disk 1,2,3,4
/dev/md0 = raid1 (1,2)
/dev/md1 = raid1 (3,4)
/dev/md2 = raid0 (stripe) (md0,md1) <--- it´s near raid10
2011/5/4 Liam Kurmos <quantum.leaf@gmail.com>:
> incidentally what does the f2 layout do that it performs so much
> better than the default?
>
> Liam
>
>
> On Thu, May 5, 2011 at 1:14 AM, Liam Kurmos <quantum.leaf@gmail.com> wrote:
>> Thanks guys!
>>
>>
>>
>>>> raid10: 220MB/s
>>>
>>> Assuming the default 'n2' layout, I would expect 2*140 or 280, so this is a
>>> little slow. Try "--layout=f2" and see what you get (should be more like
>>> RAID0).
>>
>>
>> mdadm -C /dev/md0 --level=raid10 --layout=f2 --raid-devices=4
>> /dev/sda1 /dev/sdc1 /dev/sdd1 /dev/sde1
>>
>> dd if=/dev/md0 of=/dev/null bs=1M count=1000
>> 1000+0 records in
>> 1000+0 records out
>> 1048576000 bytes (1.0 GB) copied, 2.23352 s, 469 MB/s
>>
>> :D
>>
>> awesome!!
>>
>>>
>>>> raid5: ~165MB/s
>>>
>>> I would expect 3*140 or 420, so this is very slow. I wonder if read-ahead is
>>> set badly.
>>
>>> Can you:
>>> blockdev --getra /dev/md0
>>> multiply the number it gives you by 8 and give it back with
>>> blockdev --setra NUMBER /dev/md0
>>>
>>
>> genius.
>>
>> im not really sure what this did but it totally fixed the problem.
>>
>> look ahead was 768, set it 6144 and immediately got 400MB/s
>>>
>>>> raid1: ~140MB/s (single disk speed)
>>>
>>> as expected.
>>>
>>>>
>>>> for 4 disks raid0 seems like suicide, but for my system drive the
>>>> speed advantage is so great im tempted to try it anyway and try and
>>>> use rsync to keep constant back up.
>>>
>>> If you have somewhere to rsync to, then you have more disks so RAID10 might
>>> be an answer... but I suspect you cannot move disks around that freely :-)
>>>
>>
>> no need now! f2 layout is awesome.
>>
>> many thanks,
>>
>> Liam
>>
>>
>>
>>> NeilBrown
>>>
>>>
>>>
>>>>
>>>> cheers for you responses,
>>>>
>>>> Liam
>>>
>>
> --
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--
Roberto Spadim
Spadim Technology / SPAEmpresarial
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next prev parent reply other threads:[~2011-05-05 0:25 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-05-04 0:07 mdadm raid1 read performance Liam Kurmos
2011-05-04 0:57 ` John Robinson
2011-05-06 20:44 ` Leslie Rhorer
2011-05-06 21:56 ` Keld Jørn Simonsen
2011-05-04 0:58 ` NeilBrown
2011-05-04 5:30 ` Drew
2011-05-04 6:31 ` Brad Campbell
2011-05-04 7:42 ` Roberto Spadim
2011-05-04 23:08 ` Liam Kurmos
2011-05-04 23:35 ` Roberto Spadim
2011-05-04 23:36 ` Brad Campbell
2011-05-04 23:45 ` NeilBrown
2011-05-04 23:57 ` Roberto Spadim
2011-05-05 0:14 ` Liam Kurmos
2011-05-05 0:20 ` Liam Kurmos
2011-05-05 0:25 ` Roberto Spadim [this message]
2011-05-05 0:40 ` Liam Kurmos
2011-05-05 7:26 ` David Brown
2011-05-05 10:41 ` Keld Jørn Simonsen
2011-05-05 11:38 ` David Brown
2011-05-06 4:14 ` CoolCold
2011-05-06 7:29 ` David Brown
2011-05-06 21:05 ` Leslie Rhorer
2011-05-07 10:37 ` David Brown
2011-05-07 10:58 ` Keld Jørn Simonsen
2011-05-05 0:24 ` Roberto Spadim
2011-05-05 11:10 ` Keld Jørn Simonsen
2011-05-06 21:20 ` Leslie Rhorer
2011-05-06 21:53 ` Keld Jørn Simonsen
2011-05-07 3:17 ` Leslie Rhorer
2011-05-05 4:06 ` Roman Mamedov
2011-05-05 8:06 ` Nikolay Kichukov
2011-05-05 8:39 ` Liam Kurmos
2011-05-05 8:49 ` Liam Kurmos
2011-05-05 9:30 ` NeilBrown
2011-05-04 7:48 ` David Brown
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