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Re: Disk performance hit with Dom0 vs native?



On Thu, 17 Nov 2005, Florian Heigl wrote:
Using "dd if=/dev/zero of=/dev/rwd1d bs=1m", I get about 11MB/s under Xen,
but 59MB/s with GENERIC. Is such a difference to be expected?

this is far more than I'd expect from my experience:

NetBSD xen-host-2 3.0_BETA NetBSD 3.0_BETA (XEN0) #0: Sat Aug 13 13:50:25 UTC 
2005  
builds%works.netbsd.org@localhost:/home/builds/ab/netbsd-3/i386/200508120000Z-obj/home/builds/ab/netbsd-3/src/sys/arch/i386/compile/XEN0
 i386

xen-host-2# dd if=/dev/zero of=lala bs=1024k count=1024
1024+0 records in
1024+0 records out
1073741824 bytes transferred in 19.658 secs (54621112 bytes/sec)

This might be just noise actually. I've noticed the performance plummets at around 20G through the disk (80G) to around 11MB/s from much highers speeds at either end. I think it could well be down to a duff disk (but there are no errors in dmesg).

Once again, sorry for the noise.

On an on-thread note, installed xen with 3.0_BETA for the first time this morning and it works brilliantly! Thanks to all concerned!

Can someone clarify the state of Xen 2.0 vs NetBSD 2.x and 3.0? I thought that NetBSD 2.x supported Xen 1.2 and support for 2.0 was added in 3.0 and -current (with support for 1.2 being dropped).

However, there's xentools20-2.0.7 available as a binary package for 2.0, so I'm confused. Perhaps some explanation should be added to the (excellent) HOW-TO?

--
Stephen




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