linux-kernel - Re: Slow disks.

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Date:	Sun, 26 Dec 2010 18:17:40 -0500
From:	Greg Freemyer <greg.freemyer@...il.com>
To:	Rogier Wolff <R.E.Wolff@...wizard.nl>
Cc:	Michael Tokarev <mjt@....msk.ru>, Krzysztof Halasa <khc@...waw.pl>,
	Bruno Prémont <bonbons@...ux-vserver.org>,
	linux-kernel@...r.kernel.org, linux-ide@...r.kernel.org
Subject: Re: Slow disks.

On Sun, Dec 26, 2010 at 4:40 PM, Rogier Wolff <R.E.Wolff@...wizard.nl> wrote:
> On Sat, Dec 25, 2010 at 01:14:07PM +0100, Rogier Wolff wrote:
>> Out of four partitions on the drive, two are aligned, two are not.
>
> Ooops. I looked wrong. Sorry. All four partitions are mis aligned.
>
>        Roger.

It sounds like you have 3 or 4 separate issues that are each costing
you a factor of 3 or so of pain.

3 * 3 * 3 *3 = 81  ( I don't recall how bad your overall problem was).

I can remember:

Raid 5 - poor choice for 4KB random writes - a factor of 2-4
Misaligned 4KB physical sectors - a factor of 2+
Excessive Head Parking  (You show 100K plus head parks in your smart
data) - (who knows.  It takes a while to un-park the heads and your
heads are parking way too often.)

I think you said it was a 8TB, I know its a pain, but I'd rebuild.  I
don't know how reliable various large drives are currently.  in
2008/2009 they seemed to be horrible and the advice was to use drives
from different vendors, etc so you would be less likely to have a
batch of drives go bad all at once.

Good Luck
Greg
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