[Gluster-users] [Users] Creation of preallocated disk with Gluster replication

[gregoire.leroy at retenodus.net]

Hello Darell,

Le 2014-01-08 18:47, Darrell Budic a écrit :
> Grégoire-
> 
> I think this is expected behavior. Well, at least the high glusterfsd
> CPU use during disk creation, anyway. I tried creating a 10 G disk on
> my test environment and observed similar high CPU usage by glusterfsd.
> Did the creation on the i5 system, it showed 95%-105% cpu for
> glusterfsd during creation, with the core2 system running ~35-65%
> glusterfsd utilization during the creation. Minor disk wait was
> observed on both systems, < 10% peak and generally < 5%. I imagine my
> ZFS cached backends helped a lot here. Took about 3 minutes, roughly
> what I’d expect for the i5’s disk system.

Does that mean that glusterfs + ovirt absolutely need to be separated so 
that changes on glusterfs have no negative impact on VM in production ? 
Here I got the problem with the creation of a preallocated disk but if 
tomorrow I want to change the way I replicate glusterfs bricks, I guess 
I'll have the same issue.

> Network usage was about 45%
> of the 1G link. No errors or messages logged to /var/log/messages.

If checked with iftop to be more accurate, and I can see it uses more 
than 95% with my setup.

> Depending on what your test setup looks like, I’d check my network for
> packet loss or errors first.

I did, I have 0 network error and 0% packet loss (for this latter, I 
just used ping with the ovirtmgmt interface, which showed 0% packet lost 
while my server was considered as down by Ovirt).

> Then look at my storage setup and test
> pure throughput on the disks to see what you’ve got, maybe see what
> else is running. Did you use an NFS cluster or a PosixFS cluster for
> this?

I use PosixFS cluster for this.
My detailed setup is :

Intel(R) Xeon(R) CPU E5-2420 0 @ 1.90GHz (*12), 65GB Ram
Disk (both boot and storage) : Perc H710 2To, hardware RAID 1
2 1G ethernet in bonding (failover)

Intel(R) Xeon(R) CPU E5-2609 0 @ 2.40GHz (*8), 64GB Ram
Disk (boot + storage) : Perc H310
1G ethernet

I'm pretty sure there isn't any problem with the switch between them.

To conclude :
1) About the network issue, I think it could be possible to use iptables 
with QoS rules on specific ports to limit GlusterFS throughput.
2) However, the CPU issue seems to be more difficult to avoid. I guess I 
just have to review my architecture...

Thank you,
Regards,
Grégoire Leroy