[Gluster-devel] [Gluster-users] Regarding the write performance in replica 1 volume in 1Gbps Ethernet, get about 50MB/s while writing single file.

Ramon Selga ramon.selga at gmail.com
Wed Sep 3 12:31:41 UTC 2014

Hi Jaden,

May I ask some more info about your setup?

Are you using NFS client or gluster FUSE client?

If you are using NFS Client write data goes to one of nodes of replica pair and 
that node sends write replica data to the other node. If you are using one 
switch for client and server connections and one 1GbE port on each device, data 
received in the first node is re-sended to the other node simultaneously and, in 
theory, you may reach speeds closer to 100MBps.

In case of gluster FUSE Client, write data goes simultaneously to both server 
nodes using half bandwidth for each of the client's 1GbE port because replica is 
done by client side, that results on a writing speed around 50MBps(<60MBps).

I hope this helps.

El 03/09/14 a les 07:02, Jaden Liang ha escrit:
> Hi all,
> We did some more tests and analysis yesterday. It looks like 50MB/s is the top 
> theoretical speed in replica 1 volume over 1Gbps network. GlusterFS write 
> 128KB data once a block, then wait for return. The 128KB data would cost about 
> 1ms in 1Gbps network. And in the server-side, it took about 800us to 1000us to 
> write 128KB to the HDD and return. Plus some other 100us to 200us time 
> elapsed. GlusterFS would take about 2ms-2.2ms to finish a 128KB block data 
> writing, which is about 50MB/s.
> The question is that why don't glusterfs use pipeline writting or reading to 
> speed up this chatty process?
> On Tuesday, September 2, 2014, Jaden Liang <jaden1q84 at gmail.com 
> <mailto:jaden1q84 at gmail.com>> wrote:
>     Hello, gluster-devel and gluster-users team,
>     We are running a performance test in a replica 1 volume and find out the
>     single file sequence writing performance only get about 50MB/s in a 1Gbps
>     Ethernet. However, if we test multiple files sequence writing, the writing
>     performance can go up to 120MB/s which is the top speed of network.
>     We also tried to use the stat xlator to find out where is the bottleneck
>     of single file write performance. Here is the stat data:
>     Client-side:
>     ......
>     vs_vol_rep1-client-8.latency.WRITE=total:21834371.000000us,
>     mean:2665.328491us, count:8192, max:4063475, min:1849
>     ......
>     Server-side:
>     ......
>     /data/sdb1/brick1.latency.WRITE=total:6156857.000000us, mean:751.569458us,
>     count:8192, max:230864, min:611
>     ......
>     Note that the test is write a 1GB single file sequentially to a replica 1
>     volume through 1Gbps Ethernet network.
>     On the client-side, we can see there are 8192 write requests totally.
>     Every request will write 128KB data. Total eclipsed time is 21834371us,
>     about 21 seconds. The mean time of request is 2665us, about 2.6ms which
>     means it could only serves about 380 requests in 1 seconds. Plus there are
>     other time consuming like statfs, lookup, but those are not major reasons.
>     On the server-side, the mean time of request is 751us include write data
>     to HDD disk. So we think that is not the major reason.
>     And we also modify some codes to do the statistic of system epoll elapsed
>     time. It only took about 20us from enqueue data to finish sent-out.
>     Now we are heading to the rpc mechanism in glusterfs. Still, we think this
>     issue maybe encountered in gluster-devel or gluster-users teams. Therefor,
>     any suggestions would be grateful. Or have anyone know such issue?
>     Best regards,
>     Jaden Liang
>     9/2/2014
>     -- 
>     Best regards,
>     Jaden Liang
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