[Gluster-users] Slow performance of gluster volume

Tue Sep 5 09:48:54 UTC 2017

OK my understanding is that with preallocated disks the performance with
and without shard will be the same.

In any case, please attach the volume profile[1], so we can see what else
is slowing things down.

-Krutika

[1] -
https://gluster.readthedocs.io/en/latest/Administrator%20Guide/Monitoring%20Workload/#running-glusterfs-volume-profile-command

On Tue, Sep 5, 2017 at 2:32 PM, Abi Askushi <rightkicktech at gmail.com> wrote:

> Hi Krutika,
>
> I already have a preallocated disk on VM.
> Now I am checking performance with dd on the hypervisors which have the
> gluster volume configured.
>
> I tried also several values of shard-block-size and I keep getting the
> same low values on write performance.
> Enabling client-io-threads also did not have any affect.
>
> The version of gluster I am using is glusterfs 3.8.12 built on May 11 2017
> 18:46:20.
> The setup is a set of 3 Centos 7.3 servers and ovirt 4.1, using gluster as
> storage.
>
> Below are the current settings:
>
>
> Volume Name: vms
> Type: Replicate
> Volume ID: 4513340d-7919-498b-bfe0-d836b5cea40b
> Status: Started
> Snapshot Count: 0
> Number of Bricks: 1 x (2 + 1) = 3
> Transport-type: tcp
> Bricks:
> Brick1: gluster0:/gluster/vms/brick
> Brick2: gluster1:/gluster/vms/brick
> Brick3: gluster2:/gluster/vms/brick (arbiter)
> Options Reconfigured:
> server.event-threads: 4
> client.event-threads: 4
> performance.client-io-threads: on
> features.shard-block-size: 512MB
> cluster.granular-entry-heal: enable
> performance.strict-o-direct: on
> network.ping-timeout: 30
> storage.owner-gid: 36
> storage.owner-uid: 36
> user.cifs: off
> features.shard: on
> cluster.shd-wait-qlength: 10000
> cluster.shd-max-threads: 8
> cluster.locking-scheme: granular
> cluster.data-self-heal-algorithm: full
> cluster.server-quorum-type: server
> cluster.quorum-type: auto
> cluster.eager-lock: enable
> network.remote-dio: off
> performance.low-prio-threads: 32
> performance.stat-prefetch: on
> performance.io-cache: off
> performance.read-ahead: off
> performance.quick-read: off
> transport.address-family: inet
> performance.readdir-ahead: on
> nfs.disable: on
> nfs.export-volumes: on
>
>
> I observed that when testing with dd if=/dev/zero of=testfile bs=1G
> count=1 I get 65MB/s on the vms gluster volume (and the network traffic
> between the servers reaches ~ 500Mbps), while when testing with dd
> if=/dev/zero of=testfile bs=1G count=1 *oflag=direct *I get a consistent
> 10MB/s and the network traffic hardly reaching 100Mbps.
>
> Any other things one can do?
>
> On Tue, Sep 5, 2017 at 5:57 AM, Krutika Dhananjay <kdhananj at redhat.com>
> wrote:
>
>> I'm assuming you are using this volume to store vm images, because I see
>> shard in the options list.
>>
>> Speaking from shard translator's POV, one thing you can do to improve
>> performance is to use preallocated images.
>> This will at least eliminate the need for shard to perform multiple steps
>> as part of the writes - such as creating the shard and then writing to it
>> and then updating the aggregated file size - all of which require one
>> network call each, which further get blown up once they reach AFR
>> (replicate) into many more network calls.
>>
>> Second, I'm assuming you're using the default shard block size of 4MB
>> (you can confirm this using `gluster volume get <VOL> shard-block-size`).
>> In our tests, we've found that larger shard sizes perform better. So maybe
>> change the shard-block-size to 64MB (`gluster volume set <VOL>
>> shard-block-size 64MB`).
>>
>> Third, keep stat-prefetch enabled. We've found that qemu sends quite a
>> lot of [f]stats which can be served from the (md)cache to improve
>> performance. So enable that.
>>
>> Also, could you also enable client-io-threads and see if that improves
>> performance?
>>
>> Which version of gluster are you using BTW?
>>
>> -Krutika
>>
>>
>> On Tue, Sep 5, 2017 at 4:32 AM, Abi Askushi <rightkicktech at gmail.com>
>> wrote:
>>
>>> Hi all,
>>>
>>> I have a gluster volume used to host several VMs (managed through
>>> oVirt).
>>> The volume is a replica 3 with arbiter and the 3 servers use 1 Gbit
>>> network for the storage.
>>>
>>> When testing with dd (dd if=/dev/zero of=testfile bs=1G count=1
>>> oflag=direct) out of the volume (e.g. writing at /root/) the performance of
>>> the dd is reported to be ~ 700MB/s, which is quite decent. When testing the
>>> dd on the gluster volume I get ~ 43 MB/s which way lower from the previous.
>>> When testing with dd the gluster volume, the network traffic was not
>>> exceeding 450 Mbps on the network interface. I would expect to reach near
>>> 900 Mbps considering that there is 1 Gbit of bandwidth available. This
>>> results having VMs with very slow performance (especially on their write
>>> operations).
>>>
>>> The full details of the volume are below. Any advise on what can be
>>> tweaked will be highly appreciated.
>>>
>>> Volume Name: vms
>>> Type: Replicate
>>> Volume ID: 4513340d-7919-498b-bfe0-d836b5cea40b
>>> Status: Started
>>> Snapshot Count: 0
>>> Number of Bricks: 1 x (2 + 1) = 3
>>> Transport-type: tcp
>>> Bricks:
>>> Brick1: gluster0:/gluster/vms/brick
>>> Brick2: gluster1:/gluster/vms/brick
>>> Brick3: gluster2:/gluster/vms/brick (arbiter)
>>> Options Reconfigured:
>>> cluster.granular-entry-heal: enable
>>> performance.strict-o-direct: on
>>> network.ping-timeout: 30
>>> storage.owner-gid: 36
>>> storage.owner-uid: 36
>>> user.cifs: off
>>> features.shard: on
>>> cluster.shd-wait-qlength: 10000
>>> cluster.shd-max-threads: 8
>>> cluster.locking-scheme: granular
>>> cluster.data-self-heal-algorithm: full
>>> cluster.server-quorum-type: server
>>> cluster.quorum-type: auto
>>> cluster.eager-lock: enable
>>> network.remote-dio: off
>>> performance.low-prio-threads: 32
>>> performance.stat-prefetch: off
>>> performance.io-cache: off
>>> performance.read-ahead: off
>>> performance.quick-read: off
>>> transport.address-family: inet
>>> performance.readdir-ahead: on
>>> nfs.disable: on
>>> nfs.export-volumes: on
>>>
>>>
>>> Thanx,
>>> Alex
>>>
>>> _______________________________________________
>>> Gluster-users mailing list
>>> Gluster-users at gluster.org
>>> http://lists.gluster.org/mailman/listinfo/gluster-users
>>>
>>
>>
>
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