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

Paul Hieromnimon paul.hieromnimon at gmail.com
Tue Mar 3 18:30:35 UTC 2009


>> 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.
>
This is a reason I'm interested in Solaris.  In many situations, the
software raid on Solaris (RAID-Z) is faster/cheaper/more reliable than
hardware RAID because it understands the filesystem.

>> 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. : (
I'll search the list or post a message about this one.

Thanks again.




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