From: Stan Hoeppner <stan@hardwarefreak.com>
To: Phillip Susi <psusi@ubuntu.com>, Marc MERLIN <marc@merlins.org>
Cc: linux-raid@vger.kernel.org
Subject: Re: Very long raid5 init/rebuild times
Date: Mon, 03 Feb 2014 00:34:13 -0600 [thread overview]
Message-ID: <52EF3865.4000106@hardwarefreak.com> (raw)
In-Reply-To: <52EE9445.2020202@ubuntu.com>
On 2/2/2014 12:53 PM, Phillip Susi wrote:
> On 02/01/2014 05:39 PM, Stan Hoeppner wrote:
>> It's not possible
>> to accurately measure IO throughput doing buffered writes. Thus
>> O_DIRECT is needed.
> No, you can get there just fine with buffered IO as well, unless you
> have an obscenely fast array and very slow ram, the overhead of
> buffering won't really matter for IO throughput ( just the extra cpu ).
Please reread my statement above. Now let me restate that as:
Measuring disk throughput when writing through the buffer cache isn't a
measurement of disk throughput as much as it is a measurement of cache
throughput. Thus, such measurements do not demonstrate actual disk
throughput.
Do you disagree?
--
Stan
next prev parent reply other threads:[~2014-02-03 6:34 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-01-21 7:35 Very long raid5 init/rebuild times Marc MERLIN
2014-01-21 16:37 ` Marc MERLIN
2014-01-21 17:08 ` Mark Knecht
2014-01-21 18:42 ` Chris Murphy
2014-01-22 7:55 ` Stan Hoeppner
2014-01-22 17:48 ` Marc MERLIN
2014-01-22 23:17 ` Stan Hoeppner
2014-01-23 14:28 ` John Stoffel
2014-01-24 1:02 ` Stan Hoeppner
2014-01-24 3:07 ` NeilBrown
2014-01-24 8:24 ` Stan Hoeppner
2014-01-23 2:37 ` Stan Hoeppner
2014-01-23 9:13 ` Marc MERLIN
2014-01-23 12:24 ` Stan Hoeppner
2014-01-23 21:01 ` Marc MERLIN
2014-01-24 5:13 ` Stan Hoeppner
2014-01-25 8:36 ` Marc MERLIN
2014-01-28 7:46 ` Stan Hoeppner
2014-01-28 16:50 ` Marc MERLIN
2014-01-29 0:56 ` Stan Hoeppner
2014-01-29 1:01 ` Marc MERLIN
2014-01-30 20:47 ` Phillip Susi
2014-02-01 22:39 ` Stan Hoeppner
2014-02-02 18:53 ` Phillip Susi
2014-02-03 6:34 ` Stan Hoeppner [this message]
2014-02-03 14:42 ` Phillip Susi
2014-02-04 3:30 ` Stan Hoeppner
2014-02-04 17:59 ` Larry Fenske
2014-02-04 18:08 ` Phillip Susi
2014-02-04 18:43 ` Stan Hoeppner
2014-02-04 18:55 ` Phillip Susi
2014-02-04 19:15 ` Stan Hoeppner
2014-02-04 20:16 ` Phillip Susi
2014-02-04 21:58 ` Stan Hoeppner
2014-02-05 1:19 ` Phillip Susi
2014-02-05 1:42 ` Stan Hoeppner
2014-01-30 20:36 ` Phillip Susi
2014-01-30 20:18 ` Phillip Susi
2014-01-22 19:38 ` Opal 2.0 SEDs on linux, was: " Chris Murphy
2014-01-21 18:31 ` Chris Murphy
2014-01-22 13:46 ` Ethan Wilson
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=52EF3865.4000106@hardwarefreak.com \
--to=stan@hardwarefreak.com \
--cc=linux-raid@vger.kernel.org \
--cc=marc@merlins.org \
--cc=psusi@ubuntu.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 an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.