WARNING - OLD ARCHIVES

This is an archived copy of the Xen.org mailing list, which we have preserved to ensure that existing links to archives are not broken. The live archive, which contains the latest emails, can be found at http://lists.xen.org/
   
 
 
Xen 
 
Home Products Support Community News
 
   
 

xen-users

RE: [Xen-users] Xen SAN Questions

Thanks again for the reply.

>> The reason for this was so that I could have two Xen hosts using  
>> their local storage but to also have it replicating between servers  
>> for backup purposes. Maybe I was going about this the wrong way, but  
>> I wanted to have the ability to use the large storage pool (created  
>> by the cluster) as a platform for storing VMs as well as have it  
>> back everything up on two separate locations of disk.

>I think DRDB will work here (never used it personally), but I think  
>I'd create a DRDB device for each VM and replicate each one separately  
>so you could have a primary on the remote side running a vm that can  
>be started locally if the remote site blows up and vice-versa.  You  
>don't need the added overhead of a cluster filesystem for this.  DRDB  
>will certainly add overhead for replicating writes, but this is highly  
>tweakable (consider you're replication write rate, for example, where  
>maybe you're writing to the disk at 100MB/s but only replicating at  
>10KB/s, thus saving a ton of i/o).

Alright, however we do already have the images set as raw files and converting 
some of the systems (which are running in production) to a DRBD devices might 
prove difficult. It's not a question of whether we can do that, but it is a 
good idea (for eliminating the need for clustering). I will definitely have a 
look in the replication write rate, but wouldn't a lower rate mean that some of 
the more I/O intensive VMs will lose data in the event of something going wrong?

I am kind of a newb when it comes to replication :)

And since everything is in image files, what do you think about exporting the 
DRBD'd storage as NFS for both machines to read and write? Risky? Inefficient? 

>> To clarify, the disks themselves will be a RAID-5 local to each  
>> machine (1 array per machine, 2 in total) with DRBD running between  
>> to sort of RAID-1 them over the network. Does that help? I want to  
>> take the local RAID from both machines and turn it into a SAN.

>Cool, that's fine, but don't say "SAN" here, they're different.

My mistake, sometimes I confuse terms.

Best,
Tait


_______________________________________________
Xen-users mailing list
Xen-users@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-users