Hi,
I'm planning to migrate my current server configuration:
AMD Athlon/X2 FreeBSD 62-Release 2 x 250GB HW RAID1 (all partitions RAIDed, incl. swap)
to a Xen/CentOS config:
AMD Athlon/X2 Dom0 CentOS 51 Xen 31 Dom1/1 FreeBSD 7 Dom1/2 CentOS 51 ...
To "best preserve" RAID1 mirroring protections of OS, Data, etc
*AND*
optimize performance, how should I setup RAID for the "new" configurations?
Should DOM0 be RAIDed?
Each DOM1, as well?
Should I continue to use HW RAID or switch to SW? A mix?
I understand I can do any/all ... choosing the "right" option is the goal, here.
Advice is appreciated.
Regards,
Bob Tompkins
On Dec 7, 2007 1:04 PM, Bob Tomkins bob.r350@gmail.com wrote:
To "best preserve" RAID1 mirroring protections of OS, Data, etc
*AND*optimize performance, how should I setup RAID for the "new" configurations?
The entire system I would install on HW RAID, and use LVM for flexibility in domU configurations. You can do things like take LVM snapshots and have a clone of your system available for testing, for instance.
In a recent Red Hat class that I took (RH436 - clustering and storage) we had a dom0 and several domU's - all of the domU's were actually snapshots of one "gold master" if you will, so that:
1) The amount of storage required is reduced 2) The ability to quickly rebuild one of the domU's to a "known-good" configuration.
Let me know if you have any further question!
-Jon
Hi Jon,
On Dec 7, 2007 10:57 AM, Jon Stanley jonstanley@gmail.com wrote:
The entire system I would install on HW RAID, and use LVM for flexibility in domU configurations. You can do things like take LVM snapshots and have a clone of your system available for testing, for instance.
In a recent Red Hat class that I took (RH436 - clustering and storage) we had a dom0 and several domU's - all of the domU's were actually snapshots of one "gold master" if you will, so that:
- The amount of storage required is reduced
- The ability to quickly rebuild one of the domU's to a "known-good"
configuration.
Let me know if you have any further question!
Thanks for the reply!
Generally, I've been slowly coming to the same conclusion.
Am I correct in my understanding that each DomU contains an instance of OS/kernel + app binaries in it's own virtual volume/file space, but that *data* (effectively, *any* dynamic content) is written by the DomU processes to/from the Dom0 hypervisor's volume/file space?
How about swap? Dom0 of course has its swap -- and could/should be RAIDed, but what about GuestOS' swap? I honestly haven't gotten that far yet ....
Regards,
Bob Tompkins
On Dec 7, 2007 2:33 PM, Bob Tomkins bob.r350@gmail.com wrote:
Am I correct in my understanding that each DomU contains an instance of OS/kernel + app binaries in it's own virtual volume/file space, but that *data* (effectively, *any* dynamic content) is written by the DomU processes to/from the Dom0 hypervisor's volume/file space?
Not really. Each domU has it's own storage space - which can either be a file or an LVM volume. In the instance that I described, we "fooled" the domU by actually using LVM snapshots (let me know if you're not familiar with the concept) thereby only physically having one copy of the binaries. Anything that was written to those domU's was written into the snapshot space.
How about swap? Dom0 of course has its swap -- and could/should be RAIDed, but what about GuestOS' swap? I honestly haven't gotten that far yet ....
The domU's would each have their own swap, written to whatever diskspace the domU occupies.
Hi Jon,
Not really. Each domU has it's own storage space - which can either
be a file or an LVM volume. In the instance that I described, we "fooled" the domU by actually using LVM snapshots (let me know if you're not familiar with the concept) thereby only physically having one copy of the binaries. Anything that was written to those domU's was written into the snapshot space.
How about swap? Dom0 of course has its swap -- and could/should be
RAIDed,
but what about GuestOS' swap? I honestly haven't gotten that far yet
....
The domU's would each have their own swap, written to whatever diskspace the domU occupies.
Yes, I'm familiar with LVM. But not well-versed at all in its application in a virtualized scenario.
Given the RAID-1 goal of failover & backup, and a performance goal of not bunncessarily bogging down I/O, at the moment, I'm confused by "how many copies of each object" (binay, data, swap for Dom0 and each DomU) exist in the scenario you've proposed.
I suspect much of this will be come clearer once I actually start "doing" (Hardware arriving in pieces over the next week ...).
In the meantime, I need to skectch this out on paper and stare at it for awhile -- and hope for an "aha!" moment.
Do you, perchance, have a good reference to a write-up of deploying your proposed scenario?
Regards,
Bob
-
Bob Tomkins -
Jon Stanley