Re: ls performance on directories with small number of items

Sam McLeod <mailinglists@xxxxxxxxxxx> · Tue, 28 Nov 2017 09:49:23 +1100

Hi Aaron,
We also find that Gluster is perhaps, not the most performant when performing actions on directories containing large numbers of files.
For example, with a single NFS server on the client side a recursive chown on (many!) files took about 18 seconds, our simple two replica gluster servers took over 15 minutes.
Having said that, while I'm new to the gluster world, things seem to be progressing quite quickly in regards to attempts to improve performance.

I noticed you're running a _very_ old version of Gluster, I'd first suggest upgrading to the latest stable (3.12.x) and FYI 3.13 is to be release shortly.

I'd also recommend ensuring the following setting is enabled:

performance.stat-prefetch

Further to this, additional information about the cluster / volume typology and configuration would help others assist you (but I still think you should upgrade!).

--
Sam McLeod
https://smcleod.net
https://twitter.com/s_mcleod

On 28 Nov 2017, at 12:18 am, Aaron Roberts <aroberts@xxxxxxxxxxxxxx> wrote:

Hi,
               I have a situation where an apache web server is trying to locate the IndexDocument for a directory on a gluster volume.  This URL is being hit roughly 20 times per second.  There is only 1 file in this directory.  However, the parent directory does have a large number of items (+123,000 files and dirs) and we are performing operations to move these files into 2 levels of subdirs.

We are seeing very slow response times (around 8 seconds) in apache and also when trying to ls on this dir.  Before we started the migrations to move files on the large parent dir into 2 sub levels, we weren’t aware of a problem.

[root@web-02 images]# time ls -l dir1/get/ | wc -l
2

real    0m8.114s
user    0m0.002s
sys     0m0.014s

Other directories with only 1 item return very quickly (<1 sec).

[root@Web-01 images]# time ls -l dir1/tmp1/ | wc -l
2

real    0m0.014s
user    0m0.003s
sys     0m0.006s

I’m just trying to understand what would slow down this operation so much.  Is it the high frequency of attempts to read the directory (apache hits to dir1/get/) ?  Do the move operations on items in the parent directory have any impact?

Some background info:

[root@web-02 images]# gluster --version
glusterfs 3.7.20 built on Jan 30 2017 15:39:29
Repository revision: git://git.gluster.com/glusterfs.git
Copyright (c) 2006-2011 Gluster Inc. <http://www.gluster.com>
GlusterFS comes with ABSOLUTELY NO WARRANTY.
You may redistribute copies of GlusterFS under the terms of the GNU General Public License.

[root@web-02 images]# gluster vol info

Volume Name: web_vol1
Type: Replicate
Volume ID: 0d63de20-c9c2-4931-b4a3-6aed5ae28057
Status: Started
Number of Bricks: 1 x 2 = 2
Transport-type: tcp
Bricks:
Brick1: web-01:/export/brick1/web_vol1_brick1
Brick2: web-02:/export/brick1/web_vol1_brick1
Options Reconfigured:
performance.readdir-ahead: on
performance.io-thread-count: 32
performance.cache-size: 512MB

Any insight would be gratefully received.

Thanks,
               Aaron

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