[Gluster-users] Slow write times to gluster disk
Pat Haley
phaley at mit.edu
Wed May 10 21:18:26 UTC 2017
Hi Pranith,
Since we are mounting the partitions as the bricks, I tried the dd test
writing to <brick-path>/.glusterfs/<file-to-be-removed-after-test>. The
results without oflag=sync were 1.6 Gb/s (faster than gluster but not as
fast as I was expecting given the 1.2 Gb/s to the no-gluster area w/
fewer disks).
Pat
On 05/10/2017 01:27 PM, Pranith Kumar Karampuri wrote:
>
>
> On Wed, May 10, 2017 at 10:15 PM, Pat Haley <phaley at mit.edu
> <mailto:phaley at mit.edu>> wrote:
>
>
> Hi Pranith,
>
> Not entirely sure (this isn't my area of expertise). I'll run your
> answer by some other people who are more familiar with this.
>
> I am also uncertain about how to interpret the results when we
> also add the dd tests writing to the /home area (no gluster, still
> on the same machine)
>
> * dd test without oflag=sync (rough average of multiple tests)
> o gluster w/ fuse mount : 570 Mb/s
> o gluster w/ nfs mount: 390 Mb/s
> o nfs (no gluster): 1.2 Gb/s
> * dd test with oflag=sync (rough average of multiple tests)
> o gluster w/ fuse mount: 5 Mb/s
> o gluster w/ nfs mount: 200 Mb/s
> o nfs (no gluster): 20 Mb/s
>
> Given that the non-gluster area is a RAID-6 of 4 disks while each
> brick of the gluster area is a RAID-6 of 32 disks, I would naively
> expect the writes to the gluster area to be roughly 8x faster than
> to the non-gluster.
>
>
> I think a better test is to try and write to a file using nfs without
> any gluster to a location that is not inside the brick but someother
> location that is on same disk(s). If you are mounting the partition as
> the brick, then we can write to a file inside .glusterfs directory,
> something like <brick-path>/.glusterfs/<file-to-be-removed-after-test>.
>
>
> I still think we have a speed issue, I can't tell if fuse vs nfs
> is part of the problem.
>
>
> I got interested in the post because I read that fuse speed is lesser
> than nfs speed which is counter-intuitive to my understanding. So
> wanted clarifications. Now that I got my clarifications where fuse
> outperformed nfs without sync, we can resume testing as described
> above and try to find what it is. Based on your email-id I am guessing
> you are from Boston and I am from Bangalore so if you are okay with
> doing this debugging for multiple days because of timezones, I will be
> happy to help. Please be a bit patient with me, I am under a release
> crunch but I am very curious with the problem you posted.
>
> Was there anything useful in the profiles?
>
>
> Unfortunately profiles didn't help me much, I think we are collecting
> the profiles from an active volume, so it has a lot of information
> that is not pertaining to dd so it is difficult to find the
> contributions of dd. So I went through your post again and found
> something I didn't pay much attention to earlier i.e. oflag=sync, so
> did my own tests on my setup with FUSE so sent that reply.
>
>
> Pat
>
>
>
> On 05/10/2017 12:15 PM, Pranith Kumar Karampuri wrote:
>> Okay good. At least this validates my doubts. Handling O_SYNC in
>> gluster NFS and fuse is a bit different.
>> When application opens a file with O_SYNC on fuse mount then each
>> write syscall has to be written to disk as part of the syscall
>> where as in case of NFS, there is no concept of open. NFS
>> performs write though a handle saying it needs to be a
>> synchronous write, so write() syscall is performed first then it
>> performs fsync(). so an write on an fd with O_SYNC becomes
>> write+fsync. I am suspecting that when multiple threads do this
>> write+fsync() operation on the same file, multiple writes are
>> batched together to be written do disk so the throughput on the
>> disk is increasing is my guess.
>>
>> Does it answer your doubts?
>>
>> On Wed, May 10, 2017 at 9:35 PM, Pat Haley <phaley at mit.edu
>> <mailto:phaley at mit.edu>> wrote:
>>
>>
>> Without the oflag=sync and only a single test of each, the
>> FUSE is going faster than NFS:
>>
>> FUSE:
>> mseas-data2(dri_nascar)% dd if=/dev/zero count=4096
>> bs=1048576 of=zeros.txt conv=sync
>> 4096+0 records in
>> 4096+0 records out
>> 4294967296 bytes (4.3 GB) copied, 7.46961 s, 575 MB/s
>>
>>
>> NFS
>> mseas-data2(HYCOM)% dd if=/dev/zero count=4096 bs=1048576
>> of=zeros.txt conv=sync
>> 4096+0 records in
>> 4096+0 records out
>> 4294967296 bytes (4.3 GB) copied, 11.4264 s, 376 MB/s
>>
>>
>>
>> On 05/10/2017 11:53 AM, Pranith Kumar Karampuri wrote:
>>> Could you let me know the speed without oflag=sync on both
>>> the mounts? No need to collect profiles.
>>>
>>> On Wed, May 10, 2017 at 9:17 PM, Pat Haley <phaley at mit.edu
>>> <mailto:phaley at mit.edu>> wrote:
>>>
>>>
>>> Here is what I see now:
>>>
>>> [root at mseas-data2 ~]# gluster volume info
>>>
>>> Volume Name: data-volume
>>> Type: Distribute
>>> Volume ID: c162161e-2a2d-4dac-b015-f31fd89ceb18
>>> Status: Started
>>> Number of Bricks: 2
>>> Transport-type: tcp
>>> Bricks:
>>> Brick1: mseas-data2:/mnt/brick1
>>> Brick2: mseas-data2:/mnt/brick2
>>> Options Reconfigured:
>>> diagnostics.count-fop-hits: on
>>> diagnostics.latency-measurement: on
>>> nfs.exports-auth-enable: on
>>> diagnostics.brick-sys-log-level: WARNING
>>> performance.readdir-ahead: on
>>> nfs.disable: on
>>> nfs.export-volumes: off
>>>
>>>
>>>
>>> On 05/10/2017 11:44 AM, Pranith Kumar Karampuri wrote:
>>>> Is this the volume info you have?
>>>>
>>>> >/[root at mseas-data2
>>>> <http://www.gluster.org/mailman/listinfo/gluster-users>
>>>> ~]# gluster volume info />//>/Volume Name: data-volume />/Type: Distribute />/Volume ID: c162161e-2a2d-4dac-b015-f31fd89ceb18 />/Status: Started />/Number of Bricks: 2 />/Transport-type: tcp />/Bricks: />/Brick1: mseas-data2:/mnt/brick1 />/Brick2: mseas-data2:/mnt/brick2 />/Options Reconfigured: />/performance.readdir-ahead: on />/nfs.disable: on />/nfs.export-volumes: off /
>>>> I copied this from old thread from 2016. This is
>>>> distribute volume. Did you change any of the options in
>>>> between?
>>>
>>> --
>>>
>>> -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
>>> Pat Haley Email:phaley at mit.edu <mailto:phaley at 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
>>>
>>> --
>>> Pranith
>> --
>>
>> -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
>> Pat Haley Email:phaley at mit.edu <mailto:phaley at 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
>>
>> --
>> Pranith
> --
>
> -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
> Pat Haley Email:phaley at mit.edu <mailto:phaley at 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
>
> --
> Pranith
--
-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
Pat Haley Email: phaley at 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
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