Hi Ravi,
Thanks for the reply. And yes, we are using the gluster native (fuse)
mount. Since this is not my area of expertise I have a few questions
(mostly clarifications)
Is a factor of 20 slow-down typical when compare a fuse-mounted
filesytem versus an NFS-mounted filesystem or should we also be looking
for additional issues? (Note the first dd test described below was run
on the server that hosts the file-systems so no network communication
was involved).
You also mention tweaking " write-behind xlator settings". Would you
expect better speed improvements from switching the mounting from fuse
to gnfs or from tweaking the settings? Also are these mutually
exclusive or would the be additional benefits from both switching to
gfns and tweaking?
My next question is to make sure I'm clear on the comment " if the
gluster node containing the gnfs server goes down, all mounts done using
that node will fail". If you have 2 servers, each 1 brick in the
over-all gluster FS, and one server fails, then for gnfs nothing on
either server is visible to other nodes while under fuse only the files
on the dead server are not visible. Is this what you meant?
Finally, you mention "even for gnfs mounts, you can achieve fail-over by
using CTDB". Do you know if CTDB would have any performance impact
(i.e. in a worst cast scenario could adding CTDB to gnfs erase the speed
benefits of going to gnfs in the first place)?
Thanks
Pat
On 04/08/2017 12:58 AM, Ravishankar N wrote:
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:
* on NFS disk (/home): 9.5 Gb/s
* on gluster disk (/gdata): 508 Mb/s
The gluser disk is 2 bricks joined together, no replication or
anything else. The hardware is (literally) the same:
* 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:pha...@mit.edu
Center for Ocean Engineering Phone: (617) 253-6824
Dept. of Mechanical Engineering Fax: (617) 253-8125
MIT, Room 5-213http://web.mit.edu/phaley/www/
77 Massachusetts Avenue
Cambridge, MA 02139-4301
_______________________________________________
Gluster-users mailing list
Gluster-users@gluster.org
http://lists.gluster.org/mailman/listinfo/gluster-users
--
-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
Pat Haley Email: pha...@mit.edu
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
_______________________________________________
Gluster-users mailing list
Gluster-users@gluster.org
http://lists.gluster.org/mailman/listinfo/gluster-users