Re: How to Allocate Disk Bandwidth among VMs?

[Tom Creck <tom-xen@hotmail.com>]

Thank you a lot for your reply. I will try dm-ioband for Xen disk I/O QoS
ASAP.

Actually, I'm also surveying ways of Xen disk I/O QoS. There are two kinds
of solution as I see.
One is at the frontend/backend driver level. It avoids replying on any
specific guest OS.
There are two patches for this same purpose.
The first is Xen I/O manager.  
(http://lists.xensource.com/archives/html/xen-devel/2007-07/msg00863.html)

The second is a token-based resource limitation in backend driver 
(http://www.nabble.com/-PATCH-0-2--blkback:-Token-based-QoS-resource-limiting-for-VBD-I-O.-td22808160.html)

However, my lastest Xen 3.3.0 doesn't include either. I wonder does Xen
3.3.0 incorporate any disk I/O QoS mechanism inside?

The second kind of solution, as the one you suggest, bases on Domain0 OS
kernel's scheduling of backend driver's kernel thread, such as dm-ioband and
ionice for per-process scheduling.

I tried ionice, but got no effect. I don't know why.

Is there any other idea or implementation for disk I/O QoS in Xen?



Ryo Tsuruta wrote:
> 
> Hi Tom,
> 
> # I'm sorry, I sent an empty e-mail a while ago.
> 
>>       I want to do disk I/O rate control over VMs. Therefore, I want to
>> allocate different disk I/O bandwidth for different Xen VMs on my host
>> machine. All domainUs use file-backed VBDs stored in domain0's file
>> system.
>>       Do you have any idea to do that? Hopefully it can be done by
>> modifying
>> Xend in domain0.
> 
> You can use dm-ioband for this purpose. dm-ioband is an I/O bandwidth
> controller implemented as a device-mapper driver and can control
> bandwidth on per partition, per user, per process basis.
> 
> In this case, install dm-ioband to the host OS, create a
> dm-ioband device on the disk which stores domainU's VBD files,
> and then assign bandwidth(determined proportional to the weight of
> each disk) to each virtual machine.
> 
> There is an example configuration available at:
> "Example #5: Bandwidth control for Xen blktap devices"
> http://sourceforge.net/apps/trac/ioband/wiki/dm-ioband/man/examples
> 
> Please see the following URL for more information, kernel patch files
> and binary packages for RHEL5 and CentOS5 are availble.
> http://sourceforge.net/apps/trac/ioband/wiki/dm-ioband
> 
> Please feel free to ask me if you have any questions.
> 
> Thanks,
> Ryo Tsuruta
> 
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@lists.xensource.com
> http://lists.xensource.com/xen-devel
> 
> 

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