Re: [Xen-devel] Xen disk write slowness in kernel 3.8.x

[Steven Haigh <netwiz@xxxxxxxxx>]

On 03/04/13 22:36, Felipe Franciosi wrote:
> Based on what you said later, your raid stripe size is 128KB. When you plug 
> /dev/md3 to your guest, you will be going through blkback/blkfront which only 
> support 44KB per request.
This is interesting. The default size for a RAID5/6 via mdadm these days 
is 512Kb.
> So can I ask what is the "task that is going on"?
> I mean, what is your workload and how does it look like (in terms of 
> reads/writes, (a)sync and size)?
The load is mostly sequential writes. Samba + NFS shares mainly. Files 
are usually 300Mb -> 10Gb. Its mostly writes, with occasional reads. 
Interestingly, I get 220Mb/sec+ reads - but only ~50Mb/sec writes via 
the DomU.
--
Steven Haigh

Email: netwiz@xxxxxxxxx
Web: https://www.crc.id.au
Phone: (03) 9001 6090 - 0412 935 897
Fax: (03) 8338 0299

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