| |
|
 |
|
 |
|
|
|
| |
|
|
xen-users
Re: [Xen-users] max loop xen 3.0.4
On Tue, Jan 16, 2007 at 10:50:31PM +0100, pcu-m@xxxxxxxxx wrote:
> On Tuesday 16 January 2007 17:56, Itamar Reis Peixoto wrote:
> > why you don't use tap:aio ?
>
> Why don't you tell us what it is?
>
> The Xen User's manual tells me (section A.2, disk parameter) to use
> phy:UNAME,ioemu:DEV,MODE.
>
> Somewhere else (section 6.2) it tells me to use something like
> tap:aio:/full/path/to/vm1disk,sda1,w
>
> Is the first deprecated and the second prefered?
You can use either.
However the tap:aio performs a lot better and more reliably in my
experience.
The loop version has a nasty tendency to run the kernel out of memory
when the block devices are busy. This is to do with (as I understand
it) a lack of back pressure from output file side of the loop device
back to the block device.
The tap:aio is driven by a userspace program (tapdisk) which you can
set nice levels and thus IO priority levels on.
The one downside of tap:aio is that the block devices don't appear in
xm top so you can't see at a glance how much disk IO a domain is
doing.
I don't think you can use tap:aio with an HVM domain either. At least
it didn't work when I tried it!
--
Nick Craig-Wood <nick@xxxxxxxxxxxxxx> -- http://www.craig-wood.com/nick
_______________________________________________
Xen-users mailing list
Xen-users@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-users
|
|
|
| |
|
Home