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Date: Tue, 15 Jan 2013 16:05:18 -0600
From: "Matthew D. Fuller" <fullermd@over-yonder.net>
To: Dieter BSD <dieterbsd@gmail.com>
Subject: Re: IBM blade server abysmal disk write performances
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On Tue, Jan 15, 2013 at 12:03:33PM -0800 I heard the voice of
Dieter BSD, and lo! it spake thus:
> 
> But dmesg claims "Command Queueing enabled", so you should be
> getting more than one op per rev, and writes should be fast.

Queueing would only help if your load threw multiple ops at the drive
before waiting for any of them to complete.  I'd expect a dd to a raw
device to throw a single, wait for it to return complete, then throw
the next, leading to no more than 1 op per rev.

(possibly less, with sufficiently fast revs and a sufficiently slow
system, but that's a pretty unlikely combo with platter drives and
remotely modern hardware unless it's under serious load otherwise)


-- 
Matthew Fuller     (MF4839)   |  fullermd@over-yonder.net
Systems/Network Administrator |  http://www.over-yonder.net/~fullermd/
           On the Internet, nobody can hear you scream.