Re: Very slow performance on Sharded GlusterFS

Krutika Dhananjay <kdhananj@xxxxxxxxxx> · Tue, 4 Jul 2017 12:09:20 +0530

Hi Gencer,

I just checked the volume-profile attachments.

Things that seem really odd to me as far as the sharded volume is concerned:

1. Only the replica pair having bricks 5 and 6 on both nodes 09 and 10 seems to have witnessed all the IO. No other bricks witnessed any write operations. This is unacceptable for a volume that has 8 other replica sets. Why didn't the shards get distributed across all of these sets?

2. For replica set consisting of bricks 5 and 6 of node 09, I see that the brick 5 is spending 99% of its time in FINODELK fop, when the fop that should have dominated its profile should have been in fact WRITE.

Could you throw some more light on your setup from gluster standpoint?
*
 For instance, are you using two different gluster volumes to gather 
these numbers - one distributed-replicated-striped and another 
distributed-replicated-sharded? Or are you merely converting a single 
volume from one type to another?

* And if there are indeed two volumes, could you share both their `volume info` outputs to eliminate any confusion?

* If there's just one volume, are you taking care to remove all data from the mount point of this volume before converting it?

* What is the size the test file grew to?

* These attached profiles are against dd runs? Or the file download test?

-Krutika

On Mon, Jul 3, 2017 at 8:42 PM,  <gencer@xxxxxxxxxxxxx> wrote:
Hi Krutika,

Have you be able to look out my profiles? Do you have any clue, idea or suggestion?

Thanks,
-Gencer

From: Krutika Dhananjay [mailto:kdhananj@xxxxxxxxxx] 
Sent: Friday, June 30, 2017 3:50 PM

To: gencer@xxxxxxxxxxxxx
Cc: gluster-user <gluster-users@xxxxxxxxxxx>
Subject: Re:  Very slow performance on Sharded GlusterFS

Just noticed that the way you have configured your brick order during volume-create makes both replicas of every set reside on the same machine.
That apart, do you see any difference if you change shard-block-size to 512MB? Could you try that?
If it doesn't help, could you share the volume-profile output for both the tests (separate)?
Here's what you do:
1. Start profile before starting your test - it could be dd or it could be file download.
# gluster volume profile <VOL> start
2. Run your test - again either dd or file-download.
3. Once the test has completed, run `gluster volume profile <VOL> info` and redirect its output to a tmp file.
4. Stop profile
# gluster volume profile <VOL> stop
And attach the volume-profile output file that you saved at a temporary location in step 3.
-Krutika

On Fri, Jun 30, 2017 at 5:33 PM, <gencer@xxxxxxxxxxxxx> wrote:
Hi Krutika,

Sure, here is volume info:

root@sr-09-loc-50-14-18:/# gluster volume info testvol

Volume Name: testvol
Type: Distributed-Replicate
Volume ID: 30426017-59d5-4091-b6bc-279a905b704a
Status: Started
Snapshot Count: 0
Number of Bricks: 10 x 2 = 20
Transport-type: tcp
Bricks:
Brick1: sr-09-loc-50-14-18:/bricks/brick1
Brick2: sr-09-loc-50-14-18:/bricks/brick2
Brick3: sr-09-loc-50-14-18:/bricks/brick3
Brick4: sr-09-loc-50-14-18:/bricks/brick4
Brick5: sr-09-loc-50-14-18:/bricks/brick5
Brick6: sr-09-loc-50-14-18:/bricks/brick6
Brick7: sr-09-loc-50-14-18:/bricks/brick7
Brick8: sr-09-loc-50-14-18:/bricks/brick8
Brick9: sr-09-loc-50-14-18:/bricks/brick9
Brick10: sr-09-loc-50-14-18:/bricks/brick10
Brick11: sr-10-loc-50-14-18:/bricks/brick1
Brick12: sr-10-loc-50-14-18:/bricks/brick2
Brick13: sr-10-loc-50-14-18:/bricks/brick3
Brick14: sr-10-loc-50-14-18:/bricks/brick4
Brick15: sr-10-loc-50-14-18:/bricks/brick5
Brick16: sr-10-loc-50-14-18:/bricks/brick6
Brick17: sr-10-loc-50-14-18:/bricks/brick7
Brick18: sr-10-loc-50-14-18:/bricks/brick8
Brick19: sr-10-loc-50-14-18:/bricks/brick9
Brick20: sr-10-loc-50-14-18:/bricks/brick10
Options Reconfigured:
features.shard-block-size: 32MB
features.shard: on
transport.address-family: inet
nfs.disable: on

-Gencer.

From: Krutika Dhananjay [mailto:kdhananj@xxxxxxxxxx] 
Sent: Friday, June 30, 2017 2:50 PM
To: gencer@xxxxxxxxxxxxx
Cc: gluster-user <gluster-users@xxxxxxxxxxx>
Subject: Re:  Very slow performance on Sharded GlusterFS

Could you please provide the volume-info output?
-Krutika

On Fri, Jun 30, 2017 at 4:23 PM, <gencer@xxxxxxxxxxxxx> wrote:
Hi,

I have an 2 nodes with 20 bricks in total (10+10).

First test: 

2 Nodes with Distributed – Striped – Replicated (2 x 2)
10GbE Speed between nodes

“dd” performance: 400mb/s and higher
Downloading a large file from internet and directly to the gluster: 250-300mb/s

Now same test without Stripe but with sharding. This results are same when I set shard size 4MB or 32MB. (Again 2x Replica here)

Dd performance: 70mb/s
Download directly to the gluster performance : 60mb/s

Now, If we do this test twice at the same time (two dd or two doewnload at the same time) it goes below 25/mb each or slower.

I thought sharding is at least equal or a little slower (maybe?) but these results are terribly slow.

I tried tuning (cache, window-size etc..). Nothing helps.

GlusterFS 3.11 and Debian 9 used. Kernel also tuned. Disks are “xfs” and 4TB each.

Is there any tweak/tuning out there to make it fast?

Or is this an expected behavior? If its, It is unacceptable. So slow. I cannot use this on production as it is terribly slow. 

The reason behind I use shard instead of stripe is i would like to eleminate files that bigger than brick size.

Thanks,
Gencer.

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