[Gluster-users] Slow write times to gluster disk
Pranith Kumar Karampuri
pkarampu at redhat.com
Thu May 11 16:06:14 UTC 2017
On Thu, May 11, 2017 at 9:32 PM, Pat Haley <phaley at mit.edu> wrote:
>
> Hi Pranith,
>
> The /home partition is mounted as ext4
> /home ext4 defaults,usrquota,grpquota 1 2
>
> The brick partitions are mounted ax xfs
> /mnt/brick1 xfs defaults 0 0
> /mnt/brick2 xfs defaults 0 0
>
> Will this cause a problem with creating a volume under /home?
>
I don't think the bottleneck is disk. You can do the same tests you did on
your new volume to confirm?
>
> Pat
>
>
>
> On 05/11/2017 11:32 AM, Pranith Kumar Karampuri wrote:
>
>
>
> On Thu, May 11, 2017 at 8:57 PM, Pat Haley <phaley at mit.edu> wrote:
>
>>
>> Hi Pranith,
>>
>> Unfortunately, we don't have similar hardware for a small scale test.
>> All we have is our production hardware.
>>
>
> You said something about /home partition which has lesser disks, we can
> create plain distribute volume inside one of those directories. After we
> are done, we can remove the setup. What do you say?
>
>
>>
>> Pat
>>
>>
>>
>>
>> On 05/11/2017 07:05 AM, Pranith Kumar Karampuri wrote:
>>
>>
>>
>> On Thu, May 11, 2017 at 2:48 AM, Pat Haley <phaley at mit.edu> wrote:
>>
>>>
>>> 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).
>>>
>>
>> Okay, then 1.6Gb/s is what we need to target for, considering your volume
>> is just distribute. Is there any way you can do tests on similar hardware
>> but at a small scale? Just so we can run the workload to learn more about
>> the bottlenecks in the system? We can probably try to get the speed to
>> 1.2Gb/s on your /home partition you were telling me yesterday. Let me know
>> if that is something you are okay to do.
>>
>>
>>>
>>> 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> 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)
>>>> - gluster w/ fuse mount : 570 Mb/s
>>>> - gluster w/ nfs mount: 390 Mb/s
>>>> - nfs (no gluster): 1.2 Gb/s
>>>> - dd test with oflag=sync (rough average of multiple tests)
>>>> - gluster w/ fuse mount: 5 Mb/s
>>>> - gluster w/ nfs mount: 200 Mb/s
>>>> - 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> 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> 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
>>>>>> 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
>>>>>>
>>>>>> --
>>>>> 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
>>>>>
>>>>> --
>>>> 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
>>>>
>>>> --
>>> 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
>>>
>>> --
>> 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
>>
>> --
> 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
>
>
--
Pranith
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