TESTING INFORMIX BACKUPS WITH ONBAR


Fig 1
A backup is when the Informix Engine gets data, sends it to OnBar and then OnBar sends it to the storage manager. This process will repeat itself until the engine signals there is no more data left to send. With this in mind a bottleneck can exist in only a few places.

Steps to find where the slow-down is (backup):
  1. Reduce the backup process to managable size which still exposes the throughput problem
  2. Ideally you would want to initally test backing up BAR_MAX_BACKUP number of dbspaces.
  3. Time an initial archive to act as a baseline for future timings.
  4. Time the archive using the BSALIBSUB library. You should notice that nothing is happening on the Storage manager side. That is because this library is not sending anything there. it is just throwing it away. This is important because it is measuring the maximum speed onbar can run with out any interference with the storage manager. If the storage manager is running then the library was not installed correctly.
    If there is a considerable difference between the times on #2 an #3 then the bottleneck is with the storage manager. If they are pretty close then proceed to #4.
  5. Using the READER program we will measure the speed in which the OS can read the disk(s) associated with the dbspace which is being tested. Remember to use the same block size that informix uses (8 * BUFFSIZE). If the throughput numbers are withing 10% of the same throughput numbers you got from #2 then the system is I/O bound. If there is greater than ~10% differenct in time between #2 and #3 then then problem lies somewhere with Onbar or the Informix Engine.
  6. Using the XBSAWriter Utility, Measure how fast the storage manager can receive data through the XBSA interface.
Run each of the 4 tests a few times so you can gain an average time. Your results should look like the following:

	REGULAR BACKUP			XBSAWriter
	tabdbs1	tabdbs2	tabdbs3		tabdbs1	tabdbs2	tabdbs3
Time#1	67	69	69		79	79	76	
Time#2	68	69	70		63	65	65
Time#3	66	67	68		63	66	67

	BSALibstub			Diskreader
	tabdbs1	tabdbs2	tabdbs3		tabdbs1	tabdbs2	tabdbs3
Time#1	29	29	29		26	26	26	
Time#2	29	30	29		25	26	26
Time#3	29	29	28		25	25	26
From the results above (taken from a sample test) you can see that the bottleneck lies in the Storage manager. Informix/ON-Bar can extract the data at a rate of approximately 29 Secs per dbspace. The storage manager can only receive the data at a rate of approximately 66 secs per dbspace.

Once again knowing what to tune is the most important part of effectively increasing ON-Bars performance



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