Rajesh,

It's not clear to me from Your email how long it takes
to make the level-0 backup of Your QAS.
I suppose it is about the same as Your Level-1 backup.

Is Your question why You see such a significant difference between
level-1 and level-0 on PRD and no difference on QA?

During Level-1 backup, Informix is reading from the database
EXACTLY THE SAME amount of data as during level-0 backup.
For each page IDS makes timestamp comparison to decide, whether
to put that page into L1 backup or not. The only difference
between L1 and L2 is how much data the engine is sending to tape.

It means, that in Your case, on QAS backup performance
is limited by the T3 array throughput rather then by DLT limitations.
More powerful (I suppose) production disk array can ship data
much faster to IDS for analysis, and backup performance is constrained
by the DLT limitations...


------------------------------------------
Alexey Sonkin

*
-----Original Message-----
From: Rajasekaran, Rajesh [mailto:RRajasekaran@forestpharm.com]
Sent: Thursday, April 08, 2004 4:56 PM
To: 'sapmix@iiug.org'
Cc: 'informix-list@iiug.org'
Subject: Incremental Archive performance issue......

Hi,
*** Our QAS system is a Sun E450 box with a sun storedge T/3 array attached.
Its a solaris o/s with IDS 7.31 database. The DB size is around 400 GB. Its
backup is directed over the network to a tape library attached to a master
server which is another host. Our Master server is also the* PRD box. Its a
Sun Fire V880 with Sun L40 tape libary attached. We have the Veritas
Netbackup Data center 4.5 for our backups & restores.
The QAS DB backup is going over the network to the master server's DLT tape
library that gives 35 GB/HR performance. We got that throughput for our QAS
level-0 bkup even though its over the T3 network. But the Level-1 backup has
severe performance degradation and it takes almost 5-7 hrs to complete. Our
PRD level-1's are taking anywhere btw 1.5 - 2 hrs.
We are only running the onbar whole system serial bkup. It should not put
much I/O bottlenecks since only one dbspace bkup is running at one time and
not parallel.
*I can see the iostat shows 10000-25000 Kb/sec for the T3 storedge array
continously during the level-1 bkups. The informix "onstat -g stq" shows
Full queue 0, Empty queue with Cnt 100 all the time. I dont see the I/O
bottleneck here and i dont see the problem with the Veritas Netbackup side
since our level-0 works as expected. I dont see any "arc_very_old_pages()"
running during the level-1 bkups.
Questions
1) What could be the reason for level-1 backup degradation in performance
when level-0 is performing well ?
2) What better way to monitor btw the onbar and the engine ? Will the
bar_dbug = 9 lvl trace shows* more detail towards my problem ?
Any suggestions/comments is greatly appreciated.
*
Regards
Rajesh Rajasekaran
Informix Database Administrator
Forest Pharmaceuticals Inc.
(314) 493-7073



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