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

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.

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)?


-----Original Message-----
From: xen-devel-bounces@xxxxxxxxxxxxx [mailto:xen-devel-bounces@xxxxxxxxxxxxx] 
On Behalf Of Steven Haigh
Sent: 03 April 2013 03:06
To: Xen-devel@xxxxxxxxxxxxxxxxxxx; linux-raid@xxxxxxxxxxxxxxx
Subject: [Xen-devel] Xen disk write slowness in kernel 3.8.x

# iostat -m 5
avg-cpu:  %user   %nice %system %iowait  %steal   %idle
            0.11    0.00    9.23   44.64    0.21   45.81

Device:            tps    MB_read/s    MB_wrtn/s    MB_read    MB_wrtn
sdc             286.20        17.22        34.15         86        170
sdf             284.20        17.45        34.43         87        172
sdd             217.40        17.25        34.15         86        170
sde             211.00        17.25        34.38         86        171
md3            1095.40        69.20        67.18        346        335

This is with the RAID6 mounted on /mnt/fileshare from within the Dom0. 
Speeds are about what I would expect for the task that is going on.

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