[Linux-cluster] GFS performance problem

[FM]

Thank you for the answers.

Another bottleneck that I could have is the way I connect to the SAN : 
device mapper multipath instead of the HP officiel module.

I do not not if the performance can we increase with the official module  ?




Riaan van Niekerk wrote:
> 
> 
> FM wrote:
>> Hello,
>>
>> Here is my setup :
>> RedHat Enterprise 4 (update 3).
>> 5 web servers connected to a 600 GB  GFS (noatime) on a SAN.
>> On the GFS : all web sites ROOTS and httpd logs files
>> All web servers are writing to the same log. No problem here.
>>
>> The prob is with rsync. When writing on the GSF it is very very slow !
>> (40 % slower when we are lucky :) )
>>
>> lots of question :
>> *) could it be because if I have 1 GFS for the heavy write on the log
>> and another GFS for the websites' files ?
>> *) expect for the noatime, is there other technic to speed up GFS ?
> 
> a) we have increased the number of GFS locks cached to bring them closer 
> in line with the number of locks in use:
> echo "200000" > /proc/cluster/lock_dlm/drop_count
> (not sure how much of a performance increase this got us)
> 
> b) We have disabled quotas
> gfs_tool settune /mnt/san quota_account 0
> We saw a 3 - 5 increase in performance
> 
> c) if you are using lots of small files, look into section 5.8 in the 
> GFS manual, Data Journaling. However,
> - I dont know how to change this for existing data on a GFS
> - I have asked on the mailing list, and no-one seems to be using it.
> 
>> *) Can several webserver access EXT3 FS (read only) when only on other
>> server have RW access to it ?
> 
> no. the RO server will get confused when things change from under it, 
> since it is not expecting things to change
> 
>> *) is there a options to tune rsync when using GFS ?
>> *) we are using DLM as the locking system. All servers are connected
>> with Gb RJ45. Is DLM using the network to manage the lock. And if it is
>> the case, could my problem come from the network latency ?
> 
> DLM is using the network, yes. not sure about latency. We use GB 
> ethernet with RJ45/CAT5+ and have not had any problems related to DLM 
> and the network (that we are aware of). As it was explained to me by Red 
> Hat Support, DLM is extremely efficient, being able to master/distribute 
> thousands of locks per second between nodes.
> 
>>
>> As I said, lots of questions here :)
>>
> 
> and some answers. Wish I had answers to all your questions.
> 
> greetings
> Riaan
> 
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