Hi Pat,
I'm assuming you are using gluster native (fuse mount). If it helps, you could try mounting it via gluster NFS (gnfs) and then see if there is an improvement in speed. Fuse mounts are slower than gnfs mounts but you get the benefit of avoiding a single point of failure. Unlike fuse mounts, if the gluster node containing the gnfs server goes down, all mounts done using that node will fail). For fuse mounts, you could try tweaking the write-behind xlator settings to see if it helps. See the performance.write-behind and performance.write-behind-window-size options in `gluster volume set help`. Of course, even for gnfs mounts, you can achieve fail-over by using CTDB.
Thanks,
Ravi
On 04/08/2017 12:07 AM, Pat Haley wrote:
Hi,
We noticed a dramatic slowness when writing to a gluster disk when compared to writing to an NFS disk. Specifically when using dd (data duplicator) to write a 4.3 GB file of zeros:
The gluser disk is 2 bricks joined together, no replication or anything else. The hardware is (literally) the same:
- on NFS disk (/home): 9.5 Gb/s
- on gluster disk (/gdata): 508 Mb/s
- one server with 70 hard disks and a hardware RAID card.
- 4 disks in a RAID-6 group (the NFS disk)
- 32 disks in a RAID-6 group (the max allowed by the card, /mnt/brick1)
- 32 disks in another RAID-6 group (/mnt/brick2)
- 2 hot spare
Some additional information and more tests results (after changing the log level):
glusterfs 3.7.11 built on Apr 27 2016 14:09:22
CentOS release 6.8 (Final)
RAID bus controller: LSI Logic / Symbios Logic MegaRAID SAS-3 3108 [Invader] (rev 02)
Create the file to /gdata (gluster)
[root@mseas-data2 gdata]# dd if=/dev/zero of=/gdata/zero1 bs=1M count=1000
1000+0 records in
1000+0 records out
1048576000 bytes (1.0 GB) copied, 1.91876 s, 546 MB/s
Create the file to /home (ext4)
[root@mseas-data2 gdata]# dd if=/dev/zero of=/home/zero1 bs=1M count=1000
1000+0 records in
1000+0 records out
1048576000 bytes (1.0 GB) copied, 0.686021 s, 1.5 GB/s - 3 times as fast
Copy from /gdata to /gdata (gluster to gluster)
[root@mseas-data2 gdata]# dd if=/gdata/zero1 of=/gdata/zero2
2048000+0 records in
2048000+0 records out
1048576000 bytes (1.0 GB) copied, 101.052 s, 10.4 MB/s - realllyyy slooowww
Copy from /gdata to /gdata 2nd time (gluster to gluster)
[root@mseas-data2 gdata]# dd if=/gdata/zero1 of=/gdata/zero2
2048000+0 records in
2048000+0 records out
1048576000 bytes (1.0 GB) copied, 92.4904 s, 11.3 MB/s - realllyyy slooowww again
Copy from /home to /home (ext4 to ext4)
[root@mseas-data2 gdata]# dd if=/home/zero1 of=/home/zero2
2048000+0 records in
2048000+0 records out
1048576000 bytes (1.0 GB) copied, 3.53263 s, 297 MB/s 30 times as fast
Copy from /home to /home (ext4 to ext4)
[root@mseas-data2 gdata]# dd if=/home/zero1 of=/home/zero3
2048000+0 records in
2048000+0 records out
1048576000 bytes (1.0 GB) copied, 4.1737 s, 251 MB/s - 30 times as fast
As a test, can we copy data directly to the xfs mountpoint (/mnt/brick1) and bypass gluster?
Any help you could give us would be appreciated.
Thanks
-- -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= -=-=- Pat Haley Email: phaley@xxxxxxx Center for Ocean Engineering Phone: (617) 253-6824 Dept. of Mechanical Engineering Fax: (617) 253-8125 MIT, Room 5-213 http://web.mit.edu/phaley/www/ 77 Massachusetts Avenue Cambridge, MA 02139-4301
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