From: keld@keldix.com
To: Matt Garman <matthew.garman@gmail.com>
Cc: George Spelvin <linux@horizon.com>, Mdadm <linux-raid@vger.kernel.org>
Subject: Re: Why are reads not balanced across my RAID-1?
Date: Fri, 24 Jan 2014 18:49:04 +0100 [thread overview]
Message-ID: <20140124174904.GA6884@www5.open-std.org> (raw)
In-Reply-To: <CAJvUf-BfK-CeLFZ3WmRFbSpjr_x8x1FO7pDX5gmAJyw2RpekxA@mail.gmail.com>
On Fri, Jan 24, 2014 at 08:56:02AM -0600, Matt Garman wrote:
> On Fri, Jan 24, 2014 at 6:04 AM, <keld@keldix.com> wrote:
> > The reading is not balanced because it does not make sense to do balanced
> > reads for sequential reading. In RAID-1 the disk sectors are consequitive.
> > So if you would read one sector from one disk, and the following sector from the other disk,
> > then the next read from disk 1 would need to skip a full resolvation of the disk,
> > which may cost something like 8 ms. So better read contigously from the same disk, and hope
> > for some other IO request that can use disk 2.
>
>
> Does that rationale hold for SSDs?
No, this is not relevant for SSDs as access time is almost zero.
best regards
keld
next prev parent reply other threads:[~2014-01-24 17:49 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-01-24 10:47 Why are reads not balanced across my RAID-1? George Spelvin
2014-01-24 12:04 ` keld
2014-01-24 13:33 ` George Spelvin
2014-01-25 1:48 ` keld
2014-01-24 14:56 ` Matt Garman
2014-01-24 16:50 ` Mathias Burén
2014-01-24 17:49 ` keld [this message]
2014-01-24 18:22 ` Roberto Spadim
2014-01-25 1:18 ` George Spelvin
2014-01-30 20:05 ` Phillip Susi
2014-01-25 17:52 ` Robert L Mathews
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20140124174904.GA6884@www5.open-std.org \
--to=keld@keldix.com \
--cc=linux-raid@vger.kernel.org \
--cc=linux@horizon.com \
--cc=matthew.garman@gmail.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).