[DRBD-user] high load average

Poyner, Brandon bpoyner at ccac.edu
Fri Oct 10 15:41:26 CEST 2008

Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.


As Maciej says, you might be hitting the limit of the disk.  In your circumstance where the disk accesses are slow and the load average is going up I'd take a direct look at the IO wait.  You could be spending much of your cpu cycles waiting on the disk(s).  IO wait is found in the CPU section as the 'wa' field when you run vmstat or top.  

This systemtap is useful in letting you know exactly which processes are utilizing the disk(s) the most if you're trying to figure out which process is causing the problem.  

http://sourceware.org/systemtap/wiki/ScriptsTools?action=AttachFile&do=view&target=disktop.txt

I had to install the kernel debugging packages and systemtap to get it to work.  It gives output like this...

Fri Oct 10 13:29:47 2008 , Average: 353Kb/sec, Read:    1764Kb, Write:      2Kb

     UID      PID     PPID                       CMD   DEVICE    T        BYTES
     500     3425     3424                      bash     dm-1    R      1492302
       0     3422     2037                      sshd     dm-1    R       260286
     500     3428     3427                        id     dm-1    R         6944
     500     3447     3446                        id     dm-1    R         6944
     500     3445     3444                        id     dm-1    R         5717
     500     3426     3425                     xauth     dm-1    R         3910
       0     3424     3422                      sshd     dm-1    R         3846
     500     3433     3425                     egrep     dm-1    R         3636
     500     3432     3431                 dircolors     dm-1    R         3124
     500     3430     3429                  hostname     dm-1    R         2751

Brandon Poyner
Network Engineer III
CCAC - College Office
412-237-3086

> -----Original Message-----
> From: drbd-user-bounces at lists.linbit.com [mailto:drbd-user-
> bounces at lists.linbit.com] On Behalf Of Maciej Bogucki
> Sent: Friday, October 10, 2008 2:06 AM
> To: Lorenzo Milesi
> Cc: drbd-user at lists.linbit.com
> Subject: Re: [DRBD-user] high load average
> 
> Lorenzo Milesi wrote:
> > hi
> >
> > after 6 months of usage I'm running in this problem: high load
> average!
> > When accessing the drbd device the load flies to >1, even to 2 or 5,
> > disk access is very slow, and when drbd sync is in progress it's
> almost
> > impossible to use.
> > I've been using this configuration for many months so far, without
> big
> > problems (at least like this). Now i'm running into this issue... how
> > can i debug it?
> >
> > thanks!
> >
> Hello,
> 
> Check disk utilisation. Use /iostat/ command which provides information
> about /IOPS/ and the amount of data processed during each IO. /Maybe/
> You’ve /reached Your disks barrier and You would need to add more one.
> 
> Best Regards
> Maciej Bogucki
> /
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> http://lists.linbit.com/mailman/listinfo/drbd-user


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