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Why is informix onbar backup so slow?

Byron Myers
Trusted Contributor

Why is informix onbar backup so slow?

When I run onbar with "-b" option, the backup completes in about 6 hours. When I run onbar with "-b -w" option, the backup completes in about 16 hours. What is going on?
N4000
HP-UX 11.0
Direct SCSI tape connect to STK 9490 drive
OmniBack V3.0 cell server on HP-UX 10.20 system
OmniBack V3.0 agents on client host (slow backups).
Informix Version: 7.31.UC7AX4
DB size: 137 GB
raw informix data disk: Symemtrix 3430
If you can focus your eyes far and straight enough ahead of yourself, you can see the back of your head.
14 REPLIES
harry d brown jr
Honored Contributor

Re: Why is informix onbar backup so slow?

-w option to the command, which causes it to do a "whole system" backup, which backs up all storage spaces serially

http://www.oreilly.com/catalog/unixbr/chapter/ch14.html#51700

also:

http://www.geocities.com/Heartland/Acres/4927/backup.html

Live Free or Die
Tommy Brown
Respected Contributor

Re: Why is informix onbar backup so slow?

Byron, The "advantage" is, that the Whole backup is a better recovery mechanism and must be used if the rootdbs is damaged. As you have experienced, the disadvantage is the time it takes to back up. One option is to do a "weekly" whole backup and then make certain that you back up your logical logs routinely. This would provide a recoverable procedure with a lesser time impact. I am not an expert on this, but we use the Whole backup nightly (db size < 20GB).
Tommy
I may be slow, but I get there !
Byron Myers
Trusted Contributor

Re: Why is informix onbar backup so slow?

Thanks for the responses. Here is more info. When I run the "onbar -b" the tape throughput is about 20 GB/hour, but with the "onbar -b -w" the throughput is about 9 GB/hour. Why is the throughput so much slower with the "-w" option.
If you can focus your eyes far and straight enough ahead of yourself, you can see the back of your head.
Alexander M. Ermes
Honored Contributor

Re: Why is informix onbar backup so slow?

Hi there.
I am not really sure, but can it depend on the compression ? Backup going that slow i have only seen, when i switched on software compression on a drive with hardware compression ( sample DLT 7000 ).
Rgds
Alexander M. Ermes
.. and all these memories are going to vanish like tears in the rain! final words from Rutger Hauer in "Blade Runner"
Tommy Brown
Respected Contributor

Re: Why is informix onbar backup so slow?

I think, Byron, that the DLT is not in streaming mode. Since it is a single threaded serial backup the DLT is just not being fully utilized. It would be nice if it could be incorporated with a file-system backup that would allow the multi-thread to be utilized..
Tommy
I may be slow, but I get there !

Re: Why is informix onbar backup so slow?

Hi Myers,
Can you give the detail information of Storage Manager Parameters from onconfig. I too have the same problem like the whole system backup it took me 16-18 hours and now after tunning the parameters I got the same into less than 4 hours.
If you can provide the Informix configuration file then we can look and set some speed on onbar.
Thanks
Zafar
Win/Win
Byron Myers
Trusted Contributor

Re: Why is informix onbar backup so slow?

Okay, here are the onbar parameters in the onconfig:
BAR_ACT_LOG /informix/PRD/etc/bar_act.log
BAR_BSALIB_PATH /opt/omni/lib/ob2informix.sl
BAR_MAX_BACKUP 0
BAR_NB_XPORT_COUNT 10
BAR_PROGRESS_REQ
BAR_RETRY 1
BAR_XFER_BUF_SIZE 31
RESTARTABLE_RESTORE 0
ISM_DATA_POOL ISMData
ISM_LOG_POOL ISMLogs

here are the "Tape Parameters" in onconfig
TAPDEV /dev/null
TAPEBLK 65536
TAPESIZE 7950000
LTAPEDEV /dev/null
LTAPEBLK 16384
LTAPESIZE 9300000
If you can focus your eyes far and straight enough ahead of yourself, you can see the back of your head.
Tim D Fulford
Honored Contributor

Re: Why is informix onbar backup so slow?

Hi

I'm pritty sure onbar can allow multi threading (i.e backing up more than one thing at a time). However, the -w option, as mentioned before, causes it to backup the whole database/instance serially, i.e. a single thread. This would explain the difference in the time taken & throughput.

Also there was an "OLD PAGES" bug/feature in informix 7.3? which meant that when backing up large instances it would read the pages to be backed up find out they were old & write them back to the database (updating a time index). This certainly effected the speed of ontape & I assume onbar.

Tim
-

Re: Why is informix onbar backup so slow?

Hi Myer,
You have 2K page size. I hope there is some limitations with the XBSA transport buffers for only 64Kb. I don't remember correctly but check the manual for Onbar for 7.3.
Will you try to increase the BAR_MAX_BACKUP parameter and see the result.
If you have 2 Tapes then OmniBackII can be Parallely backed-up.
But try to increase the parameter and let us know. I think you don't have to shutdown the engine also.

Thanks
Zafar
Win/Win
Byron Myers
Trusted Contributor

Re: Why is informix onbar backup so slow?

Iv'e tried various "BAR" parameters with no improvement. My SAP QA system's backups take about 6 hours with the "onbar -w" whereas, my SAP production box takes 16 hours. The DB sizes are about the same, same tape hardware, same network connections, etc.. The only difference is that my PRD system is an N4000 connected to a Symmetrix, whereas my QA system is an L2000 with JBOD.
If you can focus your eyes far and straight enough ahead of yourself, you can see the back of your head.
daniel m_1
Advisor

Re: Why is informix onbar backup so slow?

one thing to check is that you are reading from and writing to the Character device and not the Block device.
If unsure, do a ls -l on the device and look at the first character, it should be a 'c'.
-Daniel

Re: Why is informix onbar backup so slow?

Hi Myers,
OK; can you check the OmniBack Backup Specifications on both the systems and compare it. Sorry, I didn't understand about JOBD; but I know Symmetrix.

Thanks
Zafar
Win/Win
Byron Myers
Trusted Contributor

Re: Why is informix onbar backup so slow?

The OBII specifications for the "CLIENT" are similar for the informix backups. Of course, the "DEVICE", "BARLIST", etc are different.
If you can focus your eyes far and straight enough ahead of yourself, you can see the back of your head.
Dan_242
Occasional Advisor

Re: Why is informix onbar backup so slow?

slow? I can't even get mine to work correctly. From the logs I get:
# cat informix.bar_act.log
2007-02-13 14:48:51 687 686 /informix/bin/onbar_d -b -w
2007-02-13 14:48:53 687 686 ERROR: An unexpected error occurred: .
2007-02-13 14:48:53 687 686 ERROR: Could not open XBSA library /usr/lib/ibsad001.sl.
2007-02-13 14:48:53 687 686 ERROR: An unexpected error occurred: .
2007-02-13 14:48:53 687 686 ERROR: Could not open XBSA library /usr/lib/ibsad001.sl.
2007-02-13 14:48:53 687 686 ERROR: Unable to open file /informix/etc/sm_versions

What gets me is this XBSA library /usr/lib/ibsad001.sl..
Why is it looking for this? Does DLT7000 use XBSA and how can I get onbar to talk to DTL7000?

-onbar