Re: [Xen-users] Optimizing I/O

[Rudi Ahlers <rudiahlers@xxxxxxxxx>]

If possible, add as many disks to the machine as it can take, and
spread the VM's out across the disks / partitions.

Or, if you can, setup RAID 10 to help load the IO of different data
onto different disks / controllers. Don't use IDE, and try and get the
fastest disks for your budget. SATA II isn't that much more expensive
than IDE. Or if you can afford it, and the mobo can handle it, get
SCSI or SAS drives.

On Fri, Jan 23, 2009 at 7:03 AM, Craig Herring <craigeherring@xxxxxxxxx> wrote:
> I've found the biggest issue with virtualization is disk I/O. NIC I/O I have
> not seen much of an issue especially if you are using a GB nic. If you are
> having issues with NIC IO this would indicate you are possibly approaching
> 120MB/sec. Although use separate NICs for your different networks or bond
> them with ALB can help. If you are using NFS or iSCSI storage use different
> NICs than your guest networks. Also a good quality switch can assist as
> well, even sometimes overlooked. A good quality HP 1800 series switch isn't
> expensive at all. I've seen some tests that suggest Intel NICs have less
> latency, almost half, than most others.
>
> In most situations I find running a RAID 1 / RAID 10 and using less than 5
> VMs per partition is a good rule of thumb to stay away from disk contention
> issues. Also using iSCSI and DRBD can assist in speed as this would dedicate
> a server to handling disk IO. These services can also use much of the ram as
> cache. Stay away from the *fake* RAID stuff or even the cheap RAID
> controllers. Buy the better later gen 3WARE, LSI, Areca controllers or just
> use software RAID. Also format the partition XFS and set the noatime flag.
> The WD RE3/2/Raptor drives are incredibly fast especially in a RAID 1.
>
> -Craig
>
> lists@xxxxxxxxxxxx wrote:
>>
>> My question was really meant to ask about I/O, in as far as file
>> transferring between main host and network for host and guests but anything
>> is good.
>> Just trying to pull all my questions and notes together so that I can get
>> on this in a week or two and it's good to see folks sharing their ideas,
>> methods etc.
>>
>> So for example, on a system that's pretty much RPM based, what tweaks can
>> someone make to the various configurations files which would greatly help
>> overall network I/O.
>>
>> Mike
>>
>>
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>
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-- 

Kind Regards
Rudi Ahlers

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