Hey David,
Can you provide the qemu command to run each of them? What's your gluster/disk/network layout look like?
Depending on your disk and network setup you may be hitting a bottleneck there that would prevent gfapi from performing at capacity. Lots of options here that could impact things.
From: "Dave Christianson" <davidchristianson3@xxxxxxxxx>
To: gluster-users@xxxxxxxxxxx
Sent: Thursday, April 3, 2014 6:05:51 AM
Subject: [Gluster-users] No performance difference using libgfapi?
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To: gluster-users@xxxxxxxxxxx
Sent: Thursday, April 3, 2014 6:05:51 AM
Subject: [Gluster-users] No performance difference using libgfapi?
Good Morning,
In my earlier experience invoking a VM using qemu/libgfapi, I reported that it was noticeably faster than the same VM invoked from libvirt using a FUSE mount; however, this was erroneous as the qemu/libgfapi-invoked image was created using 2x the RAM and cpu's...
So, invoking the image using both methods using consistent specs of 2GB RAM and 2 cpu's, I attempted to check drive performance using the following commands:
(For regular FUSE mount I have the gluster volume mounted at /var/lib/libvirt/images.)
(For libgfapi I specify -disk file=gluster://gfs-00/gfsvol/tester1/img.)
Using libvirt/FUSE mount:
[root@tester1 ~]# hdparm -Tt /dev/vda1
/dev/vda1:
Timing cached reads: 11346 MB in 2.00 seconds = 5681.63 MB/sec
Timing buffered disk reads: 36 MB in 3.05 seconds = 11.80 MB/sec
[root@tester1 ~]# dd if=/dev/zero of=/tmp/output bs=8k count=10k; rm -f /tmp/output
10240+0 records in
10240+0 records out
41943040 bytes (42MB) copied, 0.0646241 s, 649 MB/sec
Using qemu/libgfapi:
[root@tester1 ~]# hdparm -Tt /dev/vda1
/dev/vda1:
Timing cached reads: 11998 MB in 2.00 seconds = 6008.57 MB/sec
Timing buffered disk reads: 36 MB in 3.03 seconds = 11.89 MB/sec
[root@tester1 ~]# dd if=/dev/zero of=/tmp/output bs=8k count=10k; rm -f /tmp/output
10240+0 records in
10240+0 records out
41943040 bytes (42MB) copied, 0.0621412 s, 675 MB/sec
Should I be seeing a bigger difference, or am I doing something wrong?
I'm also curious whether people have found that the performance difference is greater as the size of the gluster cluster scales up.
Thanks,
David
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