High Load average no CPU utilization

Steve Alligood steve at bluehost.com
Wed Mar 28 14:42:01 MDT 2007


it may be HOW you are mounting it, and how fedora versus BSD defaults to 
mount it.

nfs v2 will be really quick, but not as reliable for data writes (aka, udp)

nfs v3 will be more reliable (tcp) but slower

nfs v4 will be reliable (tcp) and secure (encrypted) but a lot slower

Fedora may default to v4 while your BSD does v3 or v2.


I have some mounts I use nfs v2 because I am not as worried about writes 
and I need the speed.  I also change the read and write window sizes, 
and turn off atime checking:

async,soft,noatime,intr,nfsvers=2,rsize=8192,wsize=8192

Of course, the server must support the v2 nfs as well (obvious, but 
worth mentioning)

-Steve

adam fisher wrote:
> I appreciate everybody's thoughts on this.
> 
> I agree that the NFS looks to be the bottle neck however we have 5 other load balanced web servers that are pulling the web data from our NFS server.  We mount the partition and then created sym links to those mounts.  The other 5 web boxes are up and running fine.  It is the sixth alone that is having this issue.
> 
> The first 5 are BSD this is a Fedora installation as we want to get away from BSD.  
> 
> Any other ideas?
> 
> thanks,
> Adam
> 
> 
> ----- Ryan Simpkins <plug at ryansimpkins.com> wrote:
>> On Wed, March 28, 2007 11:44, adam fisher wrote:
>>> apache   17268  0.7  0.6  29552 12868 ?        D    04:27   0:04
>> /usr/sbin/httpd
>>> apache   17456  1.1  0.6  29728 13168 ?        S    04:27   0:06
>> /usr/sbin/httpd
>>> apache   17890  0.5  0.6  29928 12588 ?        D    04:28   0:02
>> /usr/sbin/httpd
>>> apache   17893  0.0  0.5  29032 11548 ?        D    04:28   0:00
>> /usr/sbin/httpd
>>> apache   17895  0.0  0.5  29184 11716 ?        D    04:28   0:00
>> /usr/sbin/httpd
>>> apache   17896  0.0  0.5  28740 11256 ?        D    04:28   0:00
>> /usr/sbin/httpd
>>> apache   17897  0.0  0.5  28912 11452 ?        D    04:28   0:00
>> /usr/sbin/httpd
>>> apache   17904  0.3  0.5  29288 11876 ?        D    04:28   0:01
>> /usr/sbin/httpd
>>> apache   17913  0.5  0.5  29316 11892 ?        D    04:29   0:02
>> /usr/sbin/httpd
>>> apache   17923  0.1  0.5  29364 12052 ?        D    04:29   0:00
>> /usr/sbin/httpd
>>
>>> Device:         rrqm/s   wrqm/s   r/s   w/s   rsec/s   wsec/s
>> avgrq-sz avgqu-sz
>>> await  svctm  %util
>>> sda               0.00    11.00  0.00  6.00     0.00   136.00   
>> 22.67     0.00
>>> 0.50   0.17   0.10
>>> The web root is located on an NFS share.  I restarted NFS on this
>> box just to make
>>> sure.  When I restart httpd and the load average drops to around 10
>> or 11 I can
>>> browse the webpage just fine.  It is when it gets to around 150 that
>> I can't.
>> Bingo. Your web root is running over NFS. NFS is pure evil for this
>> type of work.
>> You may be able to improve performance playing around with the various
>> NFS mount
>> options.
>>
>> -Ryan
>>
>> /*
>> PLUG: http://plug.org, #utah on irc.freenode.net
>> Unsubscribe: http://plug.org/mailman/options/plug
>> Don't fear the penguin.
>> */
> 
> 
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