From: Drew <drew.kay@gmail.com>
To: NeilBrown <neilb@suse.de>
Cc: Liam Kurmos <quantum.leaf@gmail.com>, linux-raid@vger.kernel.org
Subject: Re: mdadm raid1 read performance
Date: Tue, 3 May 2011 22:30:24 -0700 [thread overview]
Message-ID: <BANLkTimzqu1C+_Z2t5m1bjduXFeRwbgssQ@mail.gmail.com> (raw)
In-Reply-To: <20110504105822.21e23bc3@notabene.brown>
>> I've been testing mdadm (great piece of software btw) however all my
>> test show that reading from raid1 is only the same speed as reading
>> from a single drive.
>
> Why do you expect RAID1 to be faster? On a single threaded sequential read
> there is not much it can do to go faster than a single device. Maybe on some
> multi-thread random IOs it might.
> What sort of tests were you running?
It wouldn't surprise me if the OP had the same idea I had when I first
started reading about RAID many moons ago.
It seemed logical to me that if two disks had the same data and we
were reading an arbitrary amount of data, why couldn't we split the
read across both disks? That way we get the benefits of pulling from
multiple disks in the read case while accepting the penalty of a write
being as slow as the slowest disk..
--
Drew
"Nothing in life is to be feared. It is only to be understood."
--Marie Curie
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next prev parent reply other threads:[~2011-05-04 5:30 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 [this message]
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
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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