[Gluster-devel] Fw: Re: Corvid gluster testing

Tue Aug 5 18:41:34 UTC 2014

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 at 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 ------
From: "Pranith Kumar Karampuri" <pkarampu at redhat.com>
To: "David Robinson" <david.robinson at corvidtec.com>
Cc: "Young Thomas" <tom.young at corvidtec.com>
Sent: 8/5/2014 2:25:38 AM
Subject: Re: Corvid gluster testing

gluster-devel at gluster.org 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]
>David.Robinson at corvidtec.com
>http://www.corvidtechnologies.com
>
>>On Aug 4, 2014, at 11:22 PM, Pranith Kumar Karampuri 
>><pkarampu at redhat.com> wrote:
>>
>>
>>>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)
>>>>
>>>>===============================
>>>>David F. Robinson, Ph.D.
>>>>President - Corvid Technologies
>>>>704.799.6944 x101 [office]
>>>>704.252.1310 [cell]
>>>>704.799.7974 [fax]
>>>>David.Robinson at corvidtec.com
>>>>http://www.corvidtechnologies.com
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