From: Roberto Spadim <roberto@spadim.com.br>
To: "Keld Jørn Simonsen" <keld@keldix.com>
Cc: "Mathias Burén" <mathias.buren@gmail.com>,
"Stan Hoeppner" <stan@hardwarefreak.com>,
"Roman Mamedov" <rm@romanrm.ru>, CoolCold <coolthecold@gmail.com>,
Linux-RAID <linux-raid@vger.kernel.org>
Subject: Re: Performance question, RAID5
Date: Mon, 31 Jan 2011 12:43:56 -0200 [thread overview]
Message-ID: <AANLkTikvRaeF449PxK0BG-fp-UJEa4WxdYRHqZH_G6CR@mail.gmail.com> (raw)
In-Reply-To: <20110131131131.GA26525@www2.open-std.org>
i think it's cpu wait i/o
2011/1/31 Keld Jørn Simonsen <keld@keldix.com>:
> On Mon, Jan 31, 2011 at 09:37:46AM +0000, Mathias Burén wrote:
>> On 31 January 2011 08:52, Keld Jørn Simonsen <keld@keldix.com> wrote:
>> > If your intallation is CPU bound, and you are
>> > using an Atom N270 processor or the like, well some ideas:
>> >
>> > The Atom CPU may have threading, so you could run 2 RAIDs
>> > which then probably would run in each thread.
>> > It would cost you 1 more disk if you run 2 RAID5's
>> > so you get 8 TB payload out of your 12 GB total (6 drives of 2 TB each).
>> >
>> > Another way to get better performance could be to use less
>> > CPU-intensitive RAID types. RAID5 is intensitive as it needs to
>> > calculate XOR information all the time. Maybe a mirrored
>> > raid type like RAID10,f2 would give you less CPU usage,
>> > and the run 2 RAIDS to have it running in both hyperthreads.
>> > Here you would then only get 6 TB payload of your 12 GB disks,
>> > but then also probably a faster system.
>> >
>> > Best regards
>> > keld
>> >
>>
>> Hi,
>>
>> It's interesting what you say about the XOR calculations. I thought
>> that it was only calculated on writes? The Atom (330) has HT, so Linux
>> sees 4 logical CPUs.
>
> Yes you are right, it only calculates XOR on writes with RAID5.
> But then I am puzzled what all these CPU cycles are used for.
> Also many cycles are used on mirrored raid types. Why?
> Maybe some is because of LVM? I have been puzzled for a long time why
> ordinary RAID without LVM need to use so much CPU. Maybe a lot of data
> sguffling between buffers? Neil?
>
> Best regards
> Keld
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--
Roberto Spadim
Spadim Technology / SPAEmpresarial
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next prev parent reply other threads:[~2011-01-31 14:43 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-01-29 22:48 Performance question, RAID5 Mathias Burén
2011-01-29 22:53 ` Roman Mamedov
2011-01-29 23:44 ` Mathias Burén
2011-01-29 23:57 ` Roman Mamedov
2011-01-30 0:15 ` Stan Hoeppner
2011-01-30 0:33 ` Mathias Burén
2011-01-30 0:27 ` Mathias Burén
2011-01-30 1:52 ` Keld Jørn Simonsen
2011-01-30 1:54 ` Mathias Burén
2011-01-30 5:56 ` Keld Jørn Simonsen
2011-01-30 12:12 ` Mathias Burén
2011-01-30 19:44 ` Stan Hoeppner
2011-01-30 19:46 ` Mathias Burén
2011-02-01 11:37 ` John Robinson
2011-02-01 13:53 ` Roberto Spadim
2011-02-01 14:02 ` Mathias Burén
2011-02-01 14:32 ` Roberto Spadim
2011-01-29 23:26 ` CoolCold
2011-01-30 0:18 ` Mathias Burén
2011-01-30 4:44 ` Roman Mamedov
2011-01-30 12:09 ` Mathias Burén
2011-01-30 12:15 ` Roman Mamedov
2011-01-30 19:41 ` Mathias Burén
2011-01-30 19:54 ` Roman Mamedov
2011-01-30 19:58 ` Mathias Burén
2011-01-30 20:03 ` Stan Hoeppner
2011-01-30 21:43 ` Mathias Burén
2011-01-31 3:39 ` Stan Hoeppner
2011-01-31 3:54 ` Roberto Spadim
2011-01-31 8:52 ` Keld Jørn Simonsen
2011-01-31 9:37 ` Mathias Burén
2011-01-31 13:11 ` Keld Jørn Simonsen
2011-01-31 14:43 ` Roberto Spadim [this message]
2011-01-31 18:44 ` Keld Jørn Simonsen
2011-01-31 20:42 ` NeilBrown
2011-01-31 21:41 ` Keld Jørn Simonsen
2011-01-31 21:43 ` Roberto Spadim
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