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From: Brad Campbell <lists2009@fnarfbargle.com>
To: Drew <drew.kay@gmail.com>
Cc: NeilBrown <neilb@suse.de>, Liam Kurmos <quantum.leaf@gmail.com>,
	linux-raid@vger.kernel.org
Subject: Re: mdadm raid1 read performance
Date: Wed, 04 May 2011 14:31:18 +0800	[thread overview]
Message-ID: <4DC0F2B6.9050708@fnarfbargle.com> (raw)
In-Reply-To: <BANLkTimzqu1C+_Z2t5m1bjduXFeRwbgssQ@mail.gmail.com>

On 04/05/11 13:30, Drew wrote:

> 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..
>
>

I would have thought as you'd be skipping alternate "stripes" on each 
disk you minimise the benefit of a readahead buffer and get subjected to 
seek and rotational latency on both disks. Overall you're benefit would 
be slim to immeasurable. Now on SSD's I could see it providing some 
extra oomph as you suffer none of the mechanical latency penalties.


  reply	other threads:[~2011-05-04  6:31 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 [this message]
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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