[Dovecot] Best Cluster Storage

[Jonathan Tripathy]

On 15/01/11 01:14, Brad Davidson wrote:
>> -----Original Message-----
>>> I'm sorry I don't follow this. It would be appreciated if you could
>>> include a simpler example. The way I see it, a VM disk is just a
> small
>>> chunck "LVM LV in my case" of a real disk.
>> Perhaps if you were to compare and contrast a virtual disk to a raw
>> disk, that would help. If you wanted to use drbd with a raw disk being
>> accessed via a VM guest, that would probably be all right. Might not
> be
>> "supported" though.
> Depending on your virtualization method, raw device passthrough would
> probably be OK. Otherwise, think about what you're doing - putting a
> filesystem - on a replicated block device - that's presented through a
> virtualization layer -  that's on a filesystem - that's on a block
> device. If you're running GFS/GlusterFS/etc on the DRBD disk, and the VM
> is on VMFS, then you're actually using two clustered filesystems!
>
> Each layer adds a bit of overhead, and each block-on-filesystem layering
> adds the potential for block misalignments and other issues that will
> affect your overall performance and throughput. It's just hard to do
> right.
>
> -Brad
Generally, I would give an LVM LV to each of my Xen guests, which 
according to the DRBD site, is ok:

http://www.drbd.org/users-guide/s-lvm-lv-as-drbd-backing-dev.html

I do not use img files with loopback devices

Is this a bit better now?