Greetings,
I am talking big performance problems here, as in 1.5MB/sec per
drive, as opposed to the stated 9MB/sec we would expect. Something has
gone awry, and I can't see what.
I have a customer with 6 DLT drives in a STK9714 attached to a
RS/6000 S7A. The S7A is running AIX 4.3.2 with fairly recent
maintenance and microcode updates (I believe). It has 10GB of memory and
8 processors. It is running ADSM 3.1.2.42. Specifically, it is
running:
adsm.afs.client.aix42 3.1.20.5 C ADSM Client - AFS File
Backup
adsm.api.client.aix42 3.1.20.7 C ADSM Client - Application
adsm.butaafs.client.aix42
adsm.butadfs.client.aix42
adsm.client.aix42.base 3.1.20.7 C ADSM Client -
Backup/Archive
adsm.client.aix42.common 3.1.20.7 C ADSM Client - Common Files
adsm.client.aix42.hsm 3.1.20.7 C ADSM Client - Hierarchical
adsm.devices.NetTAPE-tlc 3.1.2.0 C ADSM Device Support for
NetTAPE
adsm.devices.acsls 3.1.2.20 C ADSM Device Support for ACS
adsm.devices.rte 3.1.2.42 A ADSM Device Support runtime
adsm.dfs.client.aix42 3.1.20.5 C ADSM Client - DFS File
Backup
adsm.html.en_US.clients.data
adsm.html.en_US.server.data
adsm.html.en_US.unix.data 3.1.0.6 C ADSM Online Library, UNIX
Client
adsm.license.rte 3.1.2.0 C ADSM Server License
Registration
adsm.msg.en_US.emhelp 3.1.2.0 C ADSM EM Panel Help - US
English
adsm.pdf.en_US.clients.data
adsm.pdf.en_US.server.data
adsm.pdf.en_US.unix.data 3.1.0.6 C ADSM Online Library, UNIX
Client
adsm.server.gif 3.1.2.20 C ADSM Server Web
Administrator
adsm.server.rte 3.1.2.42 A ADSM Server Runtime
adsm.server.util 3.1.2.20 C ADSM Server Utilities
adsm.web.client.aix42 3.1.20.5 C ADSM Client - WebClient
adsm.webcli.client.aix42 3.1.20.7 C ADSM Client -
Backup/Archive WEB
For some time now, we have been getting only about 1.5MB/sec to each of
the DLT drives. Each is on it's own differential SCSI bus. They are
defined as /dev/mtX, using the smit devices/ADSM devices, so they are
using the ADSM drivers for the DLTs. According STK, the tape drives and
the library all have the most recent microcode updates.
The performance of the network or clients is not involved in this
problem, since the rate of 1.5MB/sec holds true even for things like
'backup stgpool' commands. Yesterday, for instance, we did a backup
stgpool maxpr=2, so there were two drives being read, and two being
written to. We copied 72GB in about 7 hours. That works out to 5.14 GB
per hour per drive being written to, or 1.46MB/sec per drive. That is
just ridiculously slow. There was a time (4-6 months ago) when the
performance was about 4.5-5.5MB/sec on the same drives, but they can't
see anything that changed drastically to account for it. However, they
were at ADSM 3.1.2.20 back then, and upgraded to .42 in an attempt to
solve a problem with occasional error in the tape library. I don't
think this change can be implicated all by itself, otherwise they would
have noticed it right away. I am not out there on a daily basis.
The S7A is fairly CPU constrained, but not memory constrained. Paging
is almost never. The performance seems to be about the same no matter
what time of day or night, so I have trouble believing the S7A is the
culprit, otherwise performance for all other processing would be very
slow, and that is not the case.
In the dsmserv.opt file, we have set:
BUFPoolsize 131072
LOGPoolsize 8192
MIRRORRead DB Normal
MIRRORWrite DB Sequential
MIRRORRead LOG Normal
MIRRORWrite LOG Parallel
which it seems like to me are the only ones that should affect
performance of a 'backup stgpool', since the network isn't involved at
that point. Bufpool is set high because the system has plenty of
memory.
The ADSM database about (4GB) is on it's own pair of disks (mirroring
at the ADSM level), and so is the ADSM log (about 1.5GB), so there
doesn't seem to be much contention at the ADSM database level or log
level.
Thanks in advance for any advice,
John Schneider
***********************************************************************
* John D. Schneider Email: jdschn AT attglobal DOT net * Phone: 636-349-4556
* Lowery Systems, Inc.
* 1329 Horan Disclaimer: Opinions expressed here are
* Fenton, MO 63026 mine and mine alone.
***********************************************************************
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