On Wed, Mar 07, 2007 at 09:58:09AM -0600, Kenneth Berry wrote:
> Hello list,
> 
> I have been working on a performance problem for about a month and I am
> out of ideas.  I hope someone can help me.  What is happening is that
> backups of large DLE that start very early seem to dump at a very slow
> rate.  Where as dumps of DLE on the same host, physical drive, etc. that
> start hours latter dump at an expected rate.  The amstatus snapshot
> below was taken at 9:30:00.  The backups start at midnight and notice
> that the dump rate for mbthome:/home/public is about 830K/sec.  But DLE
> mbthome:/home_a_i which has been running for 21 mins. is at a dump rate
> of about 9500K/sec.
> 
> -------------------------------------------------
> mbthome:/                          0    51860k finished (0:32:54)
> mbthome:/boot                      0     8431k finished (0:29:27)
> mbthome:/home/public               0 46747710k dumping 26966780k
> ( 57.69%) (0:28:31)
> mbthome:/home_a_i                  0 20529050k dumping 11973280k
> ( 58.32%) (9:09:34)
> mbthome:/home_j_k                  0 39011140k writing to tape (9:09:34)
> mbthome:/home_l_o                  0 13542210k wait for dumping
> mbthome:/home_p                    0   781310k finished (1:01:03)
> mbthome:/home_q_z                  0 10639260k wait for dumping
> mbthome:/home_rest                 0       10k finished (0:28:59)
> mbthome:/usr                       0   606581k finished (0:58:04)
> mbthome:/var                       0   330491k finished (0:38:43)
> -------------------------------------------------
> 
> I have changed many things and not found the solution yet.  I have moved
> all the data from an hardware RAID5 to a single large drive on a
> different SCSI controller.  Played with maxdumps parameter it is set at
> two for the above snap shot, for the data below the maxdump was set 1
> (default).  Top utility shows very high CPU sys levels which settles
> when dumps are finished, are mine higher than expected when amdump is
> running?

Two things I'd look at,

- are you using spindle #'s on your DLE to avoid multiple dumps from
  the same disk drive (in order to reduce thrashing)

- /home/public is singled out among the /home group.  Is it a
  different file system mounted there?  Possibly a remote network
  mount?  Is it greatly different in the type of data (lots and lots
  of small files or visa versa).  Is it different in the dumptype
  from the other /home DLEs?


-- 
Jon H. LaBadie                  jon AT jgcomp DOT com
 JG Computing
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 Princeton, NJ  08540-4322      (609) 683-7220 (fax)