From: Andreas Klauer <Andreas.Klauer@metamorpher.de>
To: "Jens-U. Mozdzen" <jmozdzen@nde.ag>
Cc: Adam Goryachev <adam@websitemanagers.com.au>, linux-raid@vger.kernel.org
Subject: Re: unbalanced RAID5 / performance issues
Date: Mon, 20 Jun 2016 11:26:00 +0200 [thread overview]
Message-ID: <20160620092600.GA3549@metamorpher.de> (raw)
In-Reply-To: <20160620104455.Horde.Cu9WNhgOSFjDC3hgl4ZCm01@www3.nde.ag>
On Mon, Jun 20, 2016 at 10:44:55AM +0200, Jens-U. Mozdzen wrote:
> Zitat von Adam Goryachev <adam@websitemanagers.com.au>:
> > As you can see, sdc (and sda) has a much higher utilisation compared
> > to all the other drives, but we can see the actual reads/writes are
> > similar across all drives.
>
> looking at those numbers, it might not be the (effective) utilization
> that's higher, but the time the SSDs spend handling the requests.
sdc also happens to be the last drive in your array.
When creating raid5, the initial sync will overwrite this drive completely.
Are you using fstrim / discard? Without TRIM this SSD might consider itself
completely full and take longer for new writes.
Also there might be an issue with SF-2281 controller used by these SSDs:
http://www.anandtech.com/show/5508/intel-ssd-520-review-cherryville-brings-reliability-to-sandforce/7
They state that even after TRIM the SSD does not return to
its prime condition...
Apart from that, double check that your partitions are aligned.
This is usually the case but may be a huge problem if overlooked.
Regards
Andreas Klauer
next prev parent reply other threads:[~2016-06-20 9:26 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-20 6:33 unbalanced RAID5 / performance issues Adam Goryachev
2016-06-20 8:44 ` Jens-U. Mozdzen
2016-06-20 9:26 ` Andreas Klauer [this message]
2016-06-20 23:41 ` Adam Goryachev
2016-06-21 2:29 ` Adam Goryachev
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=20160620092600.GA3549@metamorpher.de \
--to=andreas.klauer@metamorpher.de \
--cc=adam@websitemanagers.com.au \
--cc=jmozdzen@nde.ag \
--cc=linux-raid@vger.kernel.org \
/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.