All of lore.kernel.org
 help / color / mirror / Atom feed
From: Sebastian Riemer <sebastian.riemer@profitbricks.com>
To: linux-raid@vger.kernel.org
Subject: Reason for md raid1 max_sectors_kb limited to 127?
Date: Mon, 07 May 2012 11:41:43 +0200	[thread overview]
Message-ID: <4FA798D7.4070506@profitbricks.com> (raw)

Hi list,

I'm wondering why max_sectors_kb is set to 127 with md raid1.
This value is at 512 on normal HDDs.

If I do a file copy on ext4 on a normal HDD then I can see with
blktrace/blkparse that 128 KiB chunks are read and 512 KiB chunks are
written.

With md raid it looks like this: 124 KiB, 4 KiB, 124 KiB, 4 KiB, ... .
This looks very inefficient.

So, is there a particular reason that max_sectors_kb is set to 127?

Cheers,
Sebastian

-- 
Sebastian Riemer
Linux Kernel Developer

ProfitBricks GmbH
Greifswalder Str. 207
10405 Berlin, Germany

Tel.:  +49 - 30 - 60 98 56 991 - 303
Fax:   +49 - 30 - 51 64 09 22
Email: sebastian.riemer@profitbricks.com
Web:   http://www.profitbricks.com/

Sitz der Gesellschaft: Berlin
Registergericht: Amtsgericht Charlottenburg, HRB 125506 B
Geschäftsführer: Andreas Gauger, Achim Weiss
--
To unsubscribe from this list: send the line "unsubscribe linux-raid" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html

             reply	other threads:[~2012-05-07  9:41 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-05-07  9:41 Sebastian Riemer [this message]
2012-05-07 11:18 ` Reason for md raid1 max_sectors_kb limited to 127? NeilBrown
2012-05-07 11:34   ` Sebastian Riemer
2012-05-07 14:04     ` Bernd Schubert
2012-05-07 14:14       ` Sebastian Riemer
     [not found]         ` <CABYL=ToyVwRGOkVs63iBgfWeTsjDQ=ofsYC4hgAVpABrWbHUjA@mail.gmail.com>
2012-05-07 14:47           ` Bernd Schubert
2012-05-07 15:33             ` Sebastian Riemer
2012-05-07 16:13               ` Bernd Schubert
  -- strict thread matches above, loose matches on Subject: below --
2012-05-08 16:07 Sebastian Riemer

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=4FA798D7.4070506@profitbricks.com \
    --to=sebastian.riemer@profitbricks.com \
    --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.