Sorry for asking again for an easy way for redundant xen images. After reading some threads and numerous howtos i''m a bit confused. I have two xen hosts, each of them has one disk and should be the host for several domU''s. Live migration should be supported. If one host fails, it should be possible to boot the affected virtual machines on the other host, having the last written data available. It seems to be the best way to mount the mirrored/replicated disks in both dom0''s, create virtual groups using lvm and export logical devices to the domU''s, one logical device for each virtual machine. Maybe it''s a good idea then to use clvm to make changes of the virtual groups possible at runtime. Is there any easy to install and configure alternative to clvm? What is an easy way of mirror and mount both disks in dom0? As far as i could see, the best ways are: A) DRBD / GNBD / Some kind of shared FS OR B) Export all drives using ISCSI / Create software raid of the same disks in both dom0''s TO A): Can DRBD handle and replicate simultaneous writes to both drives in primay/primary mode? Does the use of any shared FS always needs a server/client structure? Defining one of the hosts as the filesystem server creates a single point of failure... Is this the reason for using heartbeat (to switch the server in case of failure)? Sound''s not like an easy setup... How are writes to images handled at a client of the shared fs? Are they sent to the server and then mirrored back by DRDB? Sound''s a bit like waste of ressources, doesn''t it? Can You recommend a howto for such a setup? TO B) Is it possible to have independent software raids of the same both disks in both dom0''s? Raid on host A doesn''t recognizes writes to the disks from host B, doe''s it? Maybe i misunderstood the setup... Can a software raid be configured to read only from the local disk and write to all disks (to improve performance)? Can You recommend a howto for such a setup? Can You recommend any other setup? Thank You, Marc _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Sorry for asking again for an easy way for redundant xen images. After reading some threads and numerous howtos i''m a bit confused. I have two xen hosts, each of them has one disk and should be the host for several domU''s. Live migration should be supported. If one host fails, it should be possible to boot the affected virtual machines on the other host, having the last written data available. It seems to be the best way to mount the mirrored/replicated disks in both dom0''s, create virtual groups using lvm and export logical devices to the domU''s, one logical device for each virtual machine. Maybe it''s a good idea then to use clvm to make changes of the virtual groups possible at runtime. Is there any easy to install and configure alternative to clvm? What is an easy way of mirror and mount both disks in dom0? As far as i could see, the best ways are: A) DRBD / GNBD / Some kind of shared FS OR B) Export all drives using ISCSI / Create software raid of the same disks in both dom0''s TO A): Can DRBD handle and replicate simultaneous writes to both drives in primay/primary mode? Does the use of any shared FS always needs a server/client structure? Defining one of the hosts as the filesystem server creates a single point of failure... Is this the reason for using heartbeat (to switch the server in case of failure)? Doesn''t sound like an easy setup... How are writes to images handled at a client of the shared fs? Are they sent to the server and then mirrored back by DRDB? Sound''s a bit like waste of ressources, doesn''t it? Can You recommend a good howto for such a setup? TO B) Is it possible to have independent software raids of the same both disks in both dom0''s? Raid on host A doesn''t recognizes writes to the disks from host B, doe''s it? Maybe i misunderstood the setup... Can a software raid be configured to read only from the local disk and write to all disks (to improve performance)? Can You recommend a good howto for such a setup? Can You recommend any other setup? Thank You, Marc _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
On Thu, 2008-09-25 at 09:56 +0200, Marc A. Müller wrote:> Can You recommend any other setup? >I host domU''s images on my storage network, which uses ATA-over-Ethernet. The storage nodes are basically retired servers which are recycled to work as storage nodes... Anyway, we export the LVM PVs over AoE. This has the benefit of "just working." However if you go that route, you''ll want a separate network for AoE as it eats a lot of bandwidth. But most servers have dual NICs these days. William _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Marc A. Müller <Marc.Mueller@kompetenztest.de> writes:> I have two xen hosts, each of them has one disk and should be the host > for several domU''s. Live migration should be supported. If one host > fails, it should be possible to boot the affected virtual machines on > the other host, having the last written data available.You''d better use SAN (FC, AoE, iSCSI) instead of local disks for the VM images. However, if you can''t...> It seems to be the best way to mount the mirrored/replicated disks in > both dom0''s, create virtual groups using lvm and export logical devices > to the domU''s, one logical device for each virtual machine.You don''t mount the mirrored/replicated disks but use them as PVs.> Maybe it''s a good idea then to use clvm to make changes of the virtual > groups possible at runtime. Is there any easy to install and configure > alternative to clvm?Clvm requires some setup, but really has this advantage.> What is an easy way of mirror and mount both disks in dom0?No need to mount them, run your VMs on LVs.> A) DRBD / GNBD / Some kind of shared FSNo need of shared FS is you run your VMs on LVs.> B) Export all drives using ISCSI / Create software raid of the same > disks in both dom0''sLinux software RAID isn''n cluster aware, this would result is serious data corruption. -- Feri. _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Typically, you would have a third box which acts as a SAN. It''s probably possible to use a local DRBD device between the two hosts, but I don''t like that idea. =) Thank You, Atlas Networks is an Atlas Accelerator Company From: xen-users-bounces@lists.xensource.com [mailto:xen-users-bounces@lists.xensource.com] On Behalf Of Marc A. Müller Sent: Wednesday, September 24, 2008 12:41 AM To: xen-users@lists.xensource.com Subject: [Xen-users] Best way to redundant images? Sorry for asking again for an easy way for redundant xen images. After reading some threads and numerous howtos i''m a bit confused. I have two xen hosts, each of them has one disk and should be the host for several domU''s. Live migration should be supported. If one host fails, it should be possible to boot the affected virtual machines on the other host, having the last written data available. It seems to be the best way to mount the mirrored/replicated disks in both dom0''s, create virtual groups using lvm and export logical devices to the domU''s, one logical device for each virtual machine. Maybe it''s a good idea then to use clvm to make changes of the virtual groups possible at runtime. Is there any easy to install and configure alternative to clvm? What is an easy way of mirror and mount both disks in dom0? As far as i could see, the best ways are: A) DRBD / GNBD / Some kind of shared FS OR B) Export all drives using ISCSI / Create software raid of the same disks in both dom0''s TO A): Can DRBD handle and replicate simultaneous writes to both drives in primay/primary mode? Does the use of any shared FS always needs a server/client structure? Defining one of the hosts as the filesystem server creates a single point of failure... Is this the reason for using heartbeat (to switch the server in case of failure)? Sound''s not like an easy setup... How are writes to images handled at a client of the shared fs? Are they sent to the server and then mirrored back by DRDB? Sound''s a bit like waste of ressources, doesn''t it? Can You recommend a howto for such a setup? TO B) Is it possible to have independent software raids of the same both disks in both dom0''s? Raid on host A doesn''t recognizes writes to the disks from host B, doe''s it? Maybe i misunderstood the setup... Can a software raid be configured to read only from the local disk and write to all disks (to improve performance)? Can You recommend a howto for such a setup? Can You recommend any other setup? Thank You, Marc _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users