[Gluster-users] Gluster on a Xen cloud - Questions

Nathan Stratton nathan at robotics.net
Mon Mar 2 23:00:52 UTC 2009

On Mon, 2 Mar 2009, Paul Hieromnimon wrote:

> If you replicate pairs of servers, how come you're still using RAID 6?

This is actually a very good question. So I guess their are 3 ways of 
doing this.

1) use JBOD and put a filesystem on each of the 16 drives and mount them 
on 16 points. However since gluster does not support RAID, to get 
redundancy I would need to unify 8 of the drives and distribute across the 
two sets. This would in my opinion waste a lot of disks.

2) use software RAID... the first issue is that hardware is now faster (at 
least with 3ware 9650SE cards). The second is that since my motherboard 
does not support 16 drives I would need a controller anyway, so why not 
use the free RAID?

3) Hardware RAID, the option I selected. The next question was RAID 5 or 
6. With 16 drives I found that it makes a lot of sense to use RAID 6 since 
it is very easy to run into another error before I fix a disk.

> I saw the note in the technical faq about --disable-direct-io-mode.  What
> does this do, and why is it needed to perform Xen migration?

Not sure, would need to ask someone else, all I know is it takes me from 
over 100 MB/s to 22 MB/s. : (

Nathan Stratton                                CTO, BlinkMind, Inc.
nathan at robotics.net                         nathan at blinkmind.com
http://www.robotics.net                        http://www.blinkmind.com

More information about the Gluster-users mailing list