Re: [Xen-users] Raid1 performance

[blub@xxxxxxxx]

> On Fri, Apr 09, 2010 at 11:05:40AM +0200, blub@xxxxxxxx wrote:
>> > On Thu, Apr 08, 2010 at 08:23:19PM +0200, blub@xxxxxxxx wrote:
>> >> > On Thu, Apr 08, 2010 at 07:00:11PM +0200, blub@xxxxxxxx wrote:
>> >> >> hello
>> >> >> i've been trying to achieve reasonable disk i/o performance on
>> xen.
>> >> >> on debian 5.0.4 (xen 3.2.1, kernel 2.6.26) the pv/hvm performance
>> is
>> >> >> alright with a raid1 inside the domU. unfortunately the qemu
>> version
>> >> >> (0.9.0) does not cover my needs.
>> >> >>
>> >> >> so i've been trying xen 3.4.2 & 4.0.0rc8 on gentoo (2.6.31)
>> >> >> on both versions, the disk i/o performance drops to zero when
>> copying
>> >> >> large files. initially the performance is ok (~30mbyte/s) but
>> drops
>> >> to
>> >> >> zero after ~300mb, i've tried it with wget/ftp/scp
>> >> >> this happens with both PV & HVM domU's. i've tried multiple nic
>> >> drivers
>> >> >>
>> >> >> the performance seems alright if no raid1 is running on the domU
>> >> >> i cannot run the domU raid1's on the dom0 since there are multiple
>> >> dom0s
>> >> >> connecting to multiple FC SAN's and the raid1's are done across
>> the
>> >> >> SAN's
>> >> >>
>> >> >> (btw, the performance with raid1's on the SAN's is excellent on
>> dom0)
>> >> >>
>> >> >> anyone else has experienced this issue?
>> >> >>
>> >> >
>> >> > Did you make sure dom0 has more weight than the domUs, so that it
>> is
>> >> able
>> >> > to process the IO requests?
>> >> >
>> >> > See: http://wiki.xensource.com/xenwiki/XenBestPractices
>> >> >
>> >> > -- Pasi
>> >> >
>> >> >
>> >>
>> >> yes, the box has 8 physical cores, and the domU test installation
>> only
>> >> uses two of them
>> >>
>> >
>> > How many cores does dom0 have?
>> > Did you set up the xen credit scheduler weights?
>> > Did you pin the vcpus to specific cores?
>> >
>> > What does "iostat 1" show in dom0 while you run the test?
>> > What does "xm top" show in dom0 while you run test?
>> >
>> > -- Pasi
>> >
>> >
>>
>>
>> here is the output: http://pastebin.com/c3JqU7e4
>>
>> everything looks normal in my opinion
>>
>
> Dom0 should have more weight than the domU!
>
> Was that dstat from domU or from dom0?
>
> -- Pasi
>
>
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>

dom0 hast weight 1024, domU 512

here is iostat within domU:
http://pastebin.com/0mHy8Fm1




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