I have been testing some of the fixes that Pranith incorporated into the 3.5.2-beta to see how they performed for moderate levels of i/o. All of the stability issues that I had seen in previous versions seem to have been fixed in 3.5.2; however, there still seem to be some significant performance issues. Pranith suggested that I send this to the gluster-devel email list, so here goes:
I am running an MPI job that saves a restart file to the gluster file system. When I use the following in my fstab to mount the gluster volume, the i/o time for the 2.5GB file is roughly 45-seconds.
gfsib01a.corvidtec.com:/homegfs /homegfs glusterfs transport=tcp,_netdev 0 0
When I switch this to use the NFS protocol (see below), the i/o time is 2.5-seconds.
gfsib01a.corvidtec.com:/homegfs /homegfs nfs vers=3,intr,bg,rsize=32768,wsize=32768 0 0
The read-times for gluster are 10-20% faster than NFS, but the write times are almost 20x slower.
I am running SL 6.4 and glusterfs-3.5.2-0.1.beta1.el6.x86_64...
[root@gfs01a glusterfs]# gluster volume info homegfs
Volume Name: homegfs
Type: Distributed-Replicate
Volume ID: 1e32672a-f1b7-4b58-ba94-58c085e59071
Status: Started
Number of Bricks: 2 x 2 = 4
Transport-type: tcp
Bricks:
Brick1: gfsib01a.corvidtec.com:/data/brick01a/homegfs
Brick2: gfsib01b.corvidtec.com:/data/brick01b/homegfs
Brick3: gfsib01a.corvidtec.com:/data/brick02a/homegfs
Brick4: gfsib01b.corvidtec.com:/data/brick02b/homegfs
David
------ Forwarded Message ------
Sent: 8/5/2014 2:25:38 AM
Subject: Re: Corvid gluster testing
gluster-devel@xxxxxxxxxxx is the email-id for the mailing list. We should probably start with the initial run numbers and the comparison for glusterfs mount and nfs mounts. May be something like
glusterfs mount: 90 minutes
nfs mount: 25 minutes
And profile outputs, volume config, number of mounts, hardware configuration should be a good start.
Pranith
On 08/05/2014 09:28 AM, David Robinson wrote:
Thanks pranith
===============================
David F. Robinson, Ph.D.
President - Corvid Technologies
704.799.6944 x101 [office]
704.252.1310 [cell]
704.799.7974 [fax]
On 08/05/2014 08:33 AM, Pranith Kumar Karampuri wrote:
On 08/05/2014 08:29 AM, David F. Robinson wrote:
On 08/05/2014 12:51 AM, David F. Robinson wrote:
No. I don't want to use nfs. It eliminates most of the benefits of why I want to use gluster. Failover redundancy of the pair, load balancing, etc.
What is the meaning of 'Failover redundancy of the pair, load balancing ' Could you elaborate more? smb/nfs/glusterfs are just access protocols that gluster supports functionality is almost same
Here is my understanding. Please correct me where I am wrong.
With gluster, if I am doing a write and one of the replicated pairs goes down, there is no interruption to the I/o. The failover is handled by gluster and the fuse client. This isn't done if I use an nfs mount unless the component of the pair that goes down isn't the one I used for the mount.
With nfs, I will have to mount one of the bricks. So, if I have gfs01a, gfs01b, gfs02a, gfs02b, gfs03a, gfs03b, etc and my fstab mounts gfs01a, it is my understanding that all of my I/o will go through gfs01a which then gets distributed to all of the other bricks. Gfs01a throughput becomes a bottleneck. Where if I do a gluster mount using fuse, the load balancing is handled at the client side , not the server side. If I have 1000-nodes accessing 20-gluster bricks, I need the load balancing aspect. I cannot have all traffic going through the network interface on a single brick.
If I am wrong with the above assumptions, I guess my question is why would one ever use the gluster mount instead of nfs and/or samba?
Tom: feel free to chime in if I have missed anything.
I see your point now. Yes the gluster server where you did the mount is kind of a bottle neck.
Now that we established the problem is in the clients/protocols, you should send out a detailed mail on gluster-devel and see if anyone can help with you on performance xlators that can improve it a bit more. My area of expertise is more on replication. I am sub-maintainer for replication,locks components. I also know connection management/io-threads related issues which lead to hangs as I worked on them before. Performance xlators are black box to me.
Performance xlators are enabled only on fuse gluster stack. On nfs server mounts we disable all the performance xlators except write-behind as nfs client does lots of things for improving performance. I suggest you guys follow up more on gluster-devel.
Appreciate all the help you did for improving the product :-). Thanks a ton!
Pranith
Pranith
David (Sent from mobile)
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David F. Robinson, Ph.D.
President - Corvid Technologies
704.799.6944 x101 [office]
704.252.1310 [cell]
704.799.7974 [fax]
