[Gluster-users] ls performance on directories with small number of items

[Joe Julian]

Also note, Sam's example is comparing apples and orchards. Feeding one person from an orchard is not as efficient as feeding one person an apple, but if you're feeding 10000 people... 

Also in question with the NFS example, how long until that chown was flushed? How long until another client could see those changes? That is ignoring the biggie, what happens when the NFS server goes down?

On November 27, 2017 2:49:23 PM PST, Sam McLeod <mailinglists at smcleod.net> wrote:
>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 at domicilium.com>
>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 at 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 at 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 at 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
><git://git.gluster.com/glusterfs.git>
>> Copyright (c) 2006-2011 Gluster Inc. <http://www.gluster.com
><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 at 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 <http://performance.io/>-thread-count: 32
>> performance.cache-size: 512MB
>>  
>>  
>> Any insight would be gratefully received.
>>  
>> Thanks,
>>                Aaron
>>  
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-- 
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