On Thu, Jul 31, 2008 at 12:00 PM, Chris Edwards <cedwards@xxxxxxxxxxxxxxxx>
wrote:
Hello,
I have been playing around with Xen for a few months now and I have not been
able to find any information on the differences between storing a Xen guest OS
as a image file or as a LVM. Is there performance differences? What
are the pros and cons?
Thanks for any help.
---
Chris Edwards
Chris,
Following are two tests I did to check this very thing.
Test 1 - Disk File
The disk image /dev/xvdb1 was mounted as /media/test1. The images itself was
stored on a 500 GB SATA drive. The relevent numbers are highlighted in blue.
/dev/xvdb1 10317828 154236 9639476 2% /media/test1
[root@localhost ~]# bonnie++ -s 2048 -d /media/test1 -u root
Version 1.03
------Sequential Output------ --Sequential Input- --Random-
-Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks--
Machine Size K/sec %CP K/sec %CP
K/sec %CP K/sec %CP K/sec %CP /sec %CP
localhost.locald 2G 6065
15 70595 37 20649 2 26878
53 57270 0 135.8 0
------Sequential Create------ --------Random Create--------
-Create-- --Read--- -Delete-- -Create-- --Read--- -Delete--
files /sec %CP /sec %CP /sec %CP /sec %CP /sec
%CP /sec %CP
16 17008 99 +++++ +++ 26079 90 16002
94 +++++ +++ 29094 99
localhost.localdomain,2G,6065,15,70595,37,20649,2,26878,53,57270,0,135.8,0,16,17008,99,+++++,+++,26079,90,16002,94,+++++,+++,29094,99
Test 2 - LVM
The LVM Logical Volume was created on the same 500 GB SATA drive and mounted
in the domU as /media/test2
/dev/xvdc 10321208 154236 9642684 2% /media/test2
[root@localhost ~]# bonnie++ -s 2048 -d /media/test2 -u root
Version 1.03 ------Sequential
Output------ --Sequential Input- --Random-
-Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks--
Machine Size K/sec %CP K/sec %CP K/sec
%CP K/sec %CP K/sec %CP /sec %CP
localhost.locald 2G 34825 92 50898 26 24833
4 35920 69 77594 1 137.9
0
------Sequential Create------ --------Random Create--------
-Create-- --Read--- -Delete-- -Create-- --Read--- -Delete--
files /sec %CP /sec %CP /sec %CP /sec %CP /sec
%CP /sec %CP
16 15556 92 +++++ +++ 26198 96 16281
98 +++++ +++ 28508 100
localhost.localdomain,2G,34825,92,50898,26,24833,4,35920,69,77594,1,137.9,0,16,15556,92,+++++,+++,26198,96,16281,98,+++++,+++,28508,100
INIT: version 2.86 reloading
LVM soundly trounced the disk image in Sequential Output - Per Chr by about
600% and bettered it by about 20-30% in the other tests. The one interesting
thing though was Sequential Output - Block where the disk image pulled ahead of
LVM by about 20%. This I can't account for and will need to retest because it
doesn't make a lot of sense. All of the Sequential Create/Delete stats were
within 10% of each other.
The advantage of files are you can use standard Linux copy and delete
commands to manipulate them. The advantage of LVM is it's faster and you can
benefit from LVMs ability to resize as well as create snapshots. You could of
course do this with your disk file being on the Dom0's LVM setup too by
utilizing the hosts LVM features.
Grant McWilliams
