[DRBD-user] Using DRBD for Backup and Cheap SAN ?

Christoph Adomeit Christoph.Adomeit at gatworks.de
Sat Sep 8 02:37:04 CEST 2007

Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.

> >So I played around with AOE, ISCSI, GNBD and such stuff but they
> >are all not fast enough and not reliable enough for me. So my
> >conclusion is, that ethernet-storage is not an option (except drbd
> >which is fast and reliable).
> >  
> Where were your bottleneck?
Hmm, reading performance is the bottleneck. In general I think
we can assume that on an average Server (in my setup) 90% of the
i/o is  reading and 10% is writing. Thats why I have chosen local
disks (for reading), so i take away 90% of the network load.

> >-Replicate each logical volume via drbd to one or 2 storage hosts
> >so that we have a current-copy in case of a crash.
> >-In case of a crash of a xen host I could copy the logical volumes
> >(xen vms) from the storage host to another host with another cheap 
> >harddisk or just mount the drbd partition from the storage host 
> >and continue running the server.
> >
> >  
> This could fly, but I believe you will have to maintain the same info 
> twice, the LV and the drbd resource, twice the work.
Yeah, but both, lvm and drbd are known to be performant and to "fly".

> >Maybe I could even run the drbd in master-master mode and backup a 
> >snapshot of the drbd partition instead of the drbd partition.
> >
> >  
> That one is odd, I am not sure I understand. Can you clarify?

This was an error from me, I thought I could only reliably backup
a snapshot of the drbd-slave device if it is in master-mode, but
that was nonsense, of course I can backup the snapshot of the
drbd-slave device.

The Backup of the snapshots e.g. to a local scsi-streamer on the
storage-host should be much faster than backup each and every vm 
via network.

It all should rock, I just read that I even can live-migrate my
xen-domains from one server to the other with drbd 8.0.6..

I have just decided to even get rid of the drbd-storage server.

Instead I will have 3 xen-dom0 Servers and each of them drbd-
replicates their vms to another xen-server and so I should
be able to migrate or boot a xen-vm on another server, regardless
of which server just has a problem, should be raplaced and so on. 

Christoph Adomeit
Reststrauch 191
41199 Moenchengladbach
Sitz: Moenchengladbach
Amtsgericht Moenchengladbach, HRB 6303
Christoph Adomeit, Hans Wilhelm Terstappen

Christoph.Adomeit at gatworks.de     Internetloesungen vom Feinsten
Fon. +49 2166 9149-32                      Fax. +49 2166 9149-10

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