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Re: [Qemu-devel] Re: [RFC] Disk integrity in QEMU

Subject: Re: [Qemu-devel] Re: [RFC] Disk integrity in QEMU
From: Ryan Harper
Date: Mon, 13 Oct 2008 14:15:28 -0500
* Mark Wagner <mwagner@xxxxxxxxxx> [2008-10-13 14:06]:
> Ryan Harper wrote:
> 
> Can you please post the details of the guest and host configurations. 

http://lists.gnu.org/archive/html/qemu-devel/2008-09/msg01115.html


> From seeing kvm write data that is greater than that of bare metal,
> I would think that your test dataset is too small and not
> exceeding that of the host cache size.

The size was chosen so it would fit in to demonstrate the crazy #'s seen
on cached writes without O_DSYNC.

> 
> Our previous testing has shown that once you exceed the host cache
> and cause the cache to flush, performance will drop to a point lower
> than if you didn't use the cache in the first place.
> 
> Can you repeat the tests using a data set that is 2X the size of your
> hosts memory and post the results for the community to see?

Yeah, I can generate those numbers as well.  Seeing your note about tons
of ESA and storage, feel free to generate your own #'s and post them for
the community as well; the more the merrier.

-- 
Ryan Harper
Software Engineer; Linux Technology Center
IBM Corp., Austin, Tx
(512) 838-9253   T/L: 678-9253
ryanh@xxxxxxxxxx


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