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Old 01-02-2008, 09:44 PM
Tom Lanyon
 
Default Xen, GFS, GNBD and DRBD?

Hi all,

We're looking at deploying a small Xen cluster to run some of our
smaller applications. I'm curious to get the lists opinions and advice
on what's needed.


The plan at the moment is to have two or three servers running as the
Xen dom0 hosts and two servers running as storage servers. As we're
trying to do this on a small scale, there is no means to hook the
system into our SAN, so the storage servers do not have a shared
storage subsystem.


Is it possible to run DRBD on the two storage servers and then export
the block devices over the network to the xen hosts? Ideally the goal
is to have the effect of shared storage on the xen hosts so that
domains can be migrated between them in case one server needs to go
offline. Do I run GFS on top of the DRBD mirrored device, exported via
GNBD to the xen hosts; or the other way around, using GNBD to export
the DRBD mirrored device and then GFS running on the xen hosts?


Is this possible; is there an easier/simpler/better way to do it?

Thanks,
Tom
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Old 01-02-2008, 10:25 PM
"Ross S. W. Walker"
 
Default Xen, GFS, GNBD and DRBD?

Title: Re: [CentOS] Xen, GFS, GNBD and DRBD?









Take a look at iSCSI for the storage servers. iSCSI Enterprise Target is what I use here and it works well for us.



You don't really need shared filesystems if you are doing direct block io to LVs or raw partitions as the Xen migration will handle the hand-off, but you will if you are using flat files, because of this I recommend using LVs or raw partitions as clustered filesystems will put a serious overhead on the Xen guest io.



-Ross











-----Original Message-----

From: centos-bounces@centos.org <centos-bounces@centos.org>

To: CentOS mailing list <centos@centos.org>

Sent: Wed Jan 02 17:44:19 2008

Subject: [CentOS] Xen, GFS, GNBD and DRBD?



Hi all,



We're looking at deploying a small Xen cluster to run some of our*

smaller applications. I'm curious to get the lists opinions and advice*

on what's needed.



The plan at the moment is to have two or three servers running as the*

Xen dom0 hosts and two servers running as storage servers. As we're*

trying to do this on a small scale, there is no means to hook the*

system into our SAN, so the storage servers do not have a shared*

storage subsystem.



Is it possible to run DRBD on the two storage servers and then export*

the block devices over the network to the xen hosts? Ideally the goal*

is to have the effect of shared storage on the xen hosts so that*

domains can be migrated between them in case one server needs to go*

offline. Do I run GFS on top of the DRBD mirrored device, exported via*

GNBD to the xen hosts; or the other way around, using GNBD to export*

the DRBD mirrored device and then GFS running on the xen hosts?



Is this possible; is there an easier/simpler/better way to do it?



Thanks,

Tom

_______________________________________________

CentOS mailing list

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http://lists.centos.org/mailman/listinfo/centos










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Old 01-03-2008, 12:15 AM
Tom Lanyon
 
Default Xen, GFS, GNBD and DRBD?

On 03/01/2008, at 9:55 AM, Ross S. W. Walker wrote:



Take a look at iSCSI for the storage servers. iSCSI Enterprise
Target is what I use here and it works well for us.


You don't really need shared filesystems if you are doing direct
block io to LVs or raw partitions as the Xen migration will handle
the hand-off, but you will if you are using flat files, because of
this I recommend using LVs or raw partitions as clustered
filesystems will put a serious overhead on the Xen guest io.


-Ross


Ross,

I can use DRBD to mirror data between the two storage servers and
iSCSI to export the block devices, but how will iSCSI cope with
failure of one storage server?


Can I use heartbeat and CRM to failover the host IP and iSCSI target
to the other storage server?


Regards,
Tom
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Old 01-03-2008, 12:56 AM
Ken Price
 
Default Xen, GFS, GNBD and DRBD?

Tom,

Check out the following URL. It should answer most [all?] of your
questions about creating an iSCSI target using two CentOS boxes,
Heartbeat, and DRBD.


http://www.pcpro.co.uk/realworld/82284/san-on-the-cheap.html

Hope this helps.
-Ken


Ross,

I can use DRBD to mirror data between the two storage servers and
iSCSI to export the block devices, but how will iSCSI cope with
failure of one storage server?


Can I use heartbeat and CRM to failover the host IP and iSCSI target
to the other storage server?


Regards,
Tom



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Old 01-03-2008, 07:53 AM
Marc Grimme
 
Default Xen, GFS, GNBD and DRBD?

Hi Tom,
On Wednesday 02 January 2008 23:44:19 Tom Lanyon wrote:
> Hi all,
>
> We're looking at deploying a small Xen cluster to run some of our
> smaller applications. I'm curious to get the lists opinions and advice
> on what's needed.
I'm not the biggest fan of DRBD with Xen and everything but it's for a "small"
Xen cluster isn't it ;-) . In my opinion it brings way to much complexity in
a concept that should always stay as simple as possible.
>
> The plan at the moment is to have two or three servers running as the
> Xen dom0 hosts and two servers running as storage servers. As we're
> trying to do this on a small scale, there is no means to hook the
> system into our SAN, so the storage servers do not have a shared
> storage subsystem.
>
> Is it possible to run DRBD on the two storage servers and then export
> the block devices over the network to the xen hosts? Ideally the goal
> is to have the effect of shared storage on the xen hosts so that
> domains can be migrated between them in case one server needs to go
> offline. Do I run GFS on top of the DRBD mirrored device, exported via
> GNBD to the xen hosts; or the other way around, using GNBD to export
> the DRBD mirrored device and then GFS running on the xen hosts?
>
> Is this possible; is there an easier/simpler/better way to do it?
For DRBD as base for GFS you might want to have a look at
http://gfs.wikidev.net/DRBD_Cookbook

I didn't test it but it might be what you are looking for.

When thinking about GNBD you could also think about iSCSI (as already stated)
as it is a standard. Make it highly available move it onto some other two
nodes and there you go. But still there you'll need shared storage. How about
extending your thoughts also onto NFS. Again you'll have to make it highly
available which results in shared storage or DRBD.

BTW: Don't make your *small* cluster to complex to manage. ;-)

Have fun
Marc.

--
Gruss / Regards,

Marc Grimme
http://www.atix.de/ http://www.open-sharedroot.org/

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Old 01-03-2008, 11:50 AM
"Ross S. W. Walker"
 
Default Xen, GFS, GNBD and DRBD?

Title: Re: [CentOS] Xen, GFS, GNBD and DRBD?









You can fail-over using iSCSI multi-pathing. Have the initiator log in to both targets and then setup dm-multipath to do fail-over. On the target side you could use drbd with multi primaries and there you have it, redundant storage with easy fail-over.



-Ross





-----Original Message-----

From: centos-bounces@centos.org <centos-bounces@centos.org>

To: CentOS mailing list <centos@centos.org>

Sent: Wed Jan 02 20:15:58 2008

Subject: Re: [CentOS] Xen, GFS, GNBD and DRBD?



On 03/01/2008, at 9:55 AM, Ross S. W. Walker wrote:



>

> Take a look at iSCSI for the storage servers. iSCSI Enterprise*

> Target is what I use here and it works well for us.

>

> You don't really need shared filesystems if you are doing direct*

> block io to LVs or raw partitions as the Xen migration will handle*

> the hand-off, but you will if you are using flat files, because of*

> this I recommend using LVs or raw partitions as clustered*

> filesystems will put a serious overhead on the Xen guest io.

>

> -Ross



Ross,



I can use DRBD to mirror data between the two storage servers and*

iSCSI to export the block devices, but how will iSCSI cope with*

failure of one storage server?



Can I use heartbeat and CRM to failover the host IP and iSCSI target*

to the other storage server?



Regards,

Tom

_______________________________________________

CentOS mailing list

CentOS@centos.org

http://lists.centos.org/mailman/listinfo/centos










This e-mail, and any attachments thereto, is intended only for use by
the addressee(s) named herein and may contain legally privileged
and/or confidential information. If you are not the intended recipient
of this e-mail, you are hereby notified that any dissemination,
distribution or copying of this e-mail, and any attachments thereto,
is strictly prohibited. If you have received this e-mail in error,
please immediately notify the sender and permanently delete the
original and any copy or printout thereof.


_______________________________________________
CentOS mailing list
CentOS@centos.org
http://lists.centos.org/mailman/listinfo/centos
 

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