Hey all, as a follow up to my earlier communication, it seemed that qcow might have the functionality I was looking for. I spent some time trying to get it up and going, but wasn''t making much progress. Given http://bugzilla.xensource.com/bugzilla/show_bug.cgi?id=1334 and https://bugzilla.redhat.com/show_bug.cgi?id=479315 Does this mean that CoW is broken on CentOS 5.3 with Xen 3.03? Thanks! _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
On Thu, Apr 30, 2009 at 11:18 AM, Joe Hammerman <jhammerman@videoegg.com> wrote:> Hey all, as a follow up to my earlier communication, it seemed that qcow > might have the functionality I was looking for. I spent some time trying to > get it up and going, but wasn’t making much progress.> Given> https://bugzilla.redhat.com/show_bug.cgi?id=479315> Does this mean that CoW is broken on CentOS 5.3 with Xen 3.03?Seems like it. What are your main goals? If it''s space savings, IMHO usually it''s not worthed. For example, once you do "yum update" on domU and update lots of packages (for example going from Centos 5.2 -> 5.3), it pretty much destroys whatever space-saving you may have while still having the performace penalty of qcow. This is part of the reason I like zfs volume, either directly on Opensolaris dom0 or by exporting it (via iscsi) to Linux dom0. zfs snapshot-clone feature is very efficient, and even in the event of domU''s data change a lot (like the above scenario) you can still have space savings by turning on compression and setting refreservation=0. Regards, Fajar _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
On Thu, Apr 30, 2009 at 2:02 AM, Fajar A. Nugraha <fajar@fajar.net> wrote:> This is part of the reason I like zfs volume, either directly on > Opensolaris dom0 or by exporting it (via iscsi) to Linux dom0. zfs > snapshot-clone feature is very efficient, and even in the event of > domU''s data change a lot (like the above scenario) you can still have > space savings by turning on compression and setting refreservation=0.does ZFS have block deduplication? -- Javier _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Hi Fajar,
The main goal is a to use a shared root image for a set of Virtual
Machines. Management thinks this will keep the machine more ''in
sync''. We cannot use NFS booting due to a bug in the kernel version
employed by CentOS 5.3, so that rules out UnionFS and ClusterNFS, etc.
Qcow images seemed like a pretty good way to satisfy my deliverable -
can I generate them using another utility?
Any other advice is appreciated!
Regards,
Joseph Hammerman
-----Original Message-----
From: xen-users-bounces@lists.xensource.com
[mailto:xen-users-bounces@lists.xensource.com] On Behalf Of Fajar A. Nugraha
Sent: Thursday, April 30, 2009 12:03 AM
To: Xen List
Subject: Re: [Xen-users] Qcow utilities
On Thu, Apr 30, 2009 at 11:18 AM, Joe Hammerman <jhammerman@videoegg.com>
wrote:> Hey all, as a follow up to my earlier communication, it seemed that qcow
> might have the functionality I was looking for. I spent some time trying to
> get it up and going, but wasn''t making much progress.
> Given
> https://bugzilla.redhat.com/show_bug.cgi?id=479315
> Does this mean that CoW is broken on CentOS 5.3 with Xen 3.03?
Seems like it.
What are your main goals?
If it''s space savings, IMHO usually it''s not worthed. For
example,
once you do "yum update" on domU and update lots of packages (for
example going from Centos 5.2 -> 5.3), it pretty much destroys
whatever space-saving you may have while still having the performace
penalty of qcow.
This is part of the reason I like zfs volume, either directly on
Opensolaris dom0 or by exporting it (via iscsi) to Linux dom0. zfs
snapshot-clone feature is very efficient, and even in the event of
domU''s data change a lot (like the above scenario) you can still have
space savings by turning on compression and setting refreservation=0.
Regards,
Fajar
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Joe Hammerman wrote:> The main goal is a to use a shared root image for a set of >Virtual Machines. Management thinks this will keep the machine more >''in sync''.It won''t, not unless you use it AS A SHARED FILESYSTEM If you use any form of COW image then each guest will diverge - update a file on each guest and each guest will have a separate copy of the file. You CANNOT update the base image as that would immediately corrupt ALL the images that rely on it. If you use a shared filesystem then you could stop the guests, update the shared filesystem, and restart the guests - though you may actually get away with guests running depending on what you are updating. -- Simon Hobson Visit http://www.magpiesnestpublishing.co.uk/ for books by acclaimed author Gladys Hobson. Novels - poetry - short stories - ideal as Christmas stocking fillers. Some available as e-books. _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
On 01/05/09 04:20, Javier Guerra wrote:> On Thu, Apr 30, 2009 at 2:02 AM, Fajar A. Nugraha <fajar@fajar.net> wrote: > >> This is part of the reason I like zfs volume, either directly on >> Opensolaris dom0 or by exporting it (via iscsi) to Linux dom0. zfs >> snapshot-clone feature is very efficient, and even in the event of >> domU''s data change a lot (like the above scenario) you can still have >> space savings by turning on compression and setting refreservation=0. >> > > does ZFS have block deduplication? > > > >The latest update seems integration this (northern) summer: http://mail.opensolaris.org/pipermail/zfs-code/2009-March/001058.html Jeff Williams wherethebitsroam.com _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
On Fri, May 1, 2009 at 3:20 AM, Javier Guerra <javier@guerrag.com> wrote:> does ZFS have block deduplication?Nothing usable yet. _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
On Fri, May 1, 2009 at 3:34 AM, Joe Hammerman <jhammerman@videoegg.com> wrote:> Hi Fajar, > The main goal is a to use a shared root image for a set of Virtual Machines. Management thinks this will keep the machine more ''in sync''. We cannot use NFS booting due to a bug in the kernel version employed by CentOS 5.3, so that rules out UnionFS and ClusterNFS, etc. > Qcow images seemed like a pretty good way to satisfy my deliverableIf you want "shared root image" to "keep domUs in sync", qcow is not usable. You can''t update the qcow base image. Updates will need to go to each domU, not on a centralized place. _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Granted. They actually said they want the machines to essentially have a shared filesystem, but write the differences between them to disk. The objective is not to save space but because they believe it will keep the machines more ''in sync'' (not true, as you pointed out). Is there any way to build Xen with a shared filesystem if CONFIG_NFS_ROOT cannot be enabled? There is a bug in the kernel version of CentOS 5.3, and the only work around is to compile in the functionality statically, which management has ruled out. -----Original Message----- From: xen-users-bounces@lists.xensource.com [mailto:xen-users-bounces@lists.xensource.com] On Behalf Of Simon Hobson Sent: Thursday, April 30, 2009 1:55 PM To: xen-users@lists.xensource.com Subject: RE: [Xen-users] Qcow utilities Joe Hammerman wrote:> The main goal is a to use a shared root image for a set of >Virtual Machines. Management thinks this will keep the machine more >''in sync''.It won''t, not unless you use it AS A SHARED FILESYSTEM If you use any form of COW image then each guest will diverge - update a file on each guest and each guest will have a separate copy of the file. You CANNOT update the base image as that would immediately corrupt ALL the images that rely on it. If you use a shared filesystem then you could stop the guests, update the shared filesystem, and restart the guests - though you may actually get away with guests running depending on what you are updating. -- Simon Hobson Visit http://www.magpiesnestpublishing.co.uk/ for books by acclaimed author Gladys Hobson. Novels - poetry - short stories - ideal as Christmas stocking fillers. Some available as e-books. _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
On Fri, May 1, 2009 at 11:34 AM, Joe Hammerman> Is there any way to build Xen with a shared filesystem if CONFIG_NFS_ROOT cannot be enabled? There is a bug in the kernel version of CentOS 5.3, and the only work around is to compile in the functionality statically, which management has ruled out.use a shared, minimal read-only root that nfs-mounts everything else -- Javier _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
OK what would you put in the minimal root image? Are there any use cases where this has succeeded? It seems that the minimal root file system would be just as susceptible to corruption... Thanks for taking the time to respond! -----Original Message----- From: Javier Guerra [mailto:javier@guerrag.com] Sent: Monday, May 04, 2009 7:35 AM To: Joe Hammerman Cc: Simon Hobson; xen-users@lists.xensource.com Subject: Re: [Xen-users] Qcow utilities On Fri, May 1, 2009 at 11:34 AM, Joe Hammerman> Is there any way to build Xen with a shared filesystem if CONFIG_NFS_ROOT cannot be enabled? There is a bug in the kernel version of CentOS 5.3, and the only work around is to compile in the functionality statically, which management has ruled out.use a shared, minimal read-only root that nfs-mounts everything else -- Javier _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
On Mon, May 4, 2009 at 11:50 AM, Joe Hammerman <jhammerman@videoegg.com> wrote:> OK what would you put in the minimal root image? Are there any use cases where this has succeeded? It seems that the minimal root file system would be just as susceptible to corruption...that''s why it has to be read only! :-) i''d contemplate two options: 1: (easier): do a full but small install of your preferred distro, use it as read-only, and add NFS for /etc, /var, /home... principal con: you can''t change anything on that root without taking down all DomU''s that use it. 2: (funnier): check busybox, it makes it easy to create a complete bootable root filesystem on less than 10MB. just add a few scripts to mount your NFS. principal con: the busybox shell environment is functional but not comfortable, you have to add most of the usual things via NFS, maybe bind-remount over ''startup'' directories, or using chroot to make most of your system beleive the NFS is the root. -- Javier _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users