From: Stan Hoeppner <stan@hardwarefreak.com>
To: stan@hardwarefreak.com
Cc: Jason Newton <nevion@gmail.com>, xfs@oss.sgi.com
Subject: Re: realtime section bugs still around
Date: Fri, 03 Aug 2012 06:28:29 -0500 [thread overview]
Message-ID: <501BB5DD.1000302@hardwarefreak.com> (raw)
In-Reply-To: <501A58DB.7070801@hardwarefreak.com>
On 8/2/2012 5:39 AM, Stan Hoeppner wrote:
> We already gave you the biggest cause of your latency, which is garbage
> collection/wear leveling. You can't see inside the SSDs, but you can
> see the latency jump with either top (%wa) or iostat (await,
> milliseconds). Run
>
> iostat -x -d 1 20
>
> and you get 20 reports 1 second apart. 1s is minimum granularity. This
> should clearly show the latency spikes caused by the SSDs. Maybe even
> execute it for 60 seconds and pipe to a file.
The above assumes Linux can see the individual devices. I've never used
Intel's fakeraid. If its driver presents a single device to the kernel
instead of both SSD devices, iostat won't show which SSD's garbage
collection is kicking in and/or when. It would be most beneficial if
you could see the iostat data for both SSD devices as it would tell you
exactly when each drive's GC/leveling kicks in. If the Intel fakeraid
doesn't allow you to see both devices, you'll need to switch to md/RAID.
I'm sure that will be problematic as you're very likely booting from
the Intel RAIDed SSD device.
--
Stan
_______________________________________________
xfs mailing list
xfs@oss.sgi.com
http://oss.sgi.com/mailman/listinfo/xfs
prev parent reply other threads:[~2012-08-03 11:28 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-07-27 8:14 realtime section bugs still around Jason Newton
2012-07-27 9:56 ` Stan Hoeppner
2012-07-30 3:03 ` Dave Chinner
[not found] ` <CAGou9MheeBWxajd65szNfDB2L+VVoZ7SypEdUKj7np3L0H8fHA@mail.gmail.com>
2012-07-31 23:01 ` Jason Newton
2012-07-31 23:46 ` Stan Hoeppner
[not found] ` <CAGou9MhneejOuhX4c8G06c3Zh7dxF-OtZ+=mT-7fho_u1Q3zWw@mail.gmail.com>
2012-08-01 3:55 ` Stan Hoeppner
2012-08-01 5:55 ` Jason Newton
2012-08-02 0:39 ` Stan Hoeppner
2012-08-02 2:38 ` Jason Newton
2012-08-02 10:39 ` Stan Hoeppner
2012-08-03 11:28 ` Stan Hoeppner [this message]
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=501BB5DD.1000302@hardwarefreak.com \
--to=stan@hardwarefreak.com \
--cc=nevion@gmail.com \
--cc=xfs@oss.sgi.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.