Re: [Xen-users] Xen Image File vs LVM

[Nuno Fernandes <npf-mlists@xxxxxxxxxxx>]

On Monday 04 August 2008 20:46:17 Chris Edwards wrote:
> Thanks for the tip.  So can I ask a few questions on setting up Xen with
> LV's?
>
>
>
> 1.        Do I need to create a separate LV for each xen guest os?
Yeap.

>
> 2.        Can you point me in the right direction for doing LV snap shots?

Not possible in current clvmd implementation.

>
> 3.        If I have a xen guest os in a LV how would I migrate the guest os
> from one machine to the other?  Create identical LV on new machine?
Using clvmd.

Best regards,

./npf


>
>
>
>
> Again, Thanks for the info.   I have been having a hard time finding the
> answers to these questions.
>
>
>
> ---
>
> Chris Edwards
> Smartech Corp.
> Div. of AirNet Group
>
> http://www.airnetgroup.com <http://www.airnetgroup.com/>
>
> http://www.smartechcorp.net <http://www.smartechcorp.net/>
>
> cedwards@xxxxxxxxxxxxxxxx <mailto:agarrison@xxxxxxxxxxxxxxxx>
> P:  423-664-7678 x114
>
> C:  423-593-6964
>
> F:  423-664-7680
>
>
>
> From: xen-users-bounces@xxxxxxxxxxxxxxxxxxx
> [mailto:xen-users-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Grant
> McWilliams Sent: Thursday, July 31, 2008 3:35 PM
> To: Chris Edwards
> Cc: xen-users@xxxxxxxxxxxxxxxxxxx
> Subject: Re: [Xen-users] Xen Image File vs LVM
>
>
>
>
>
> 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,
>1 6,17008,99,+++++,+++,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



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