The need to use multiple data systems

12. Feb, 2010 0 Comments

I’ve come across a number of customer sites that have only a single backup stream from each client running sequentially to a tape drive device. While there is a concern that the time to recover increases if you have multiplexed data on a tape, there is also a need to properly stream the tape drive. For the most part these nice little pieces of hardware do not have a slow speed and will be required to stop and restart as data is presented. This is known as “shoe shining” and can take a large toll on the device resulting in frequent repairs and even slower backups.

The following examples expand each step in multiplexing backups to illustrate how all tape drive devices should be used.

Each example shows 5 Clients, each client having 4 possible jobs streams
Each stream runs at 5 MB/Sec
Tape device can handle 80MB/Sec

Figure A
The example in Figure A shows the consecutive approach currently deployed causing a cascading slow down affect. There is simply not enough data being presented to the tape drive for it to stream effectively.

Figure B
The example in Figure B is an improvement as each client can send a backup to the tape drive, shortening the overall backup window, and utilizing the tape drive at 20MB/Sec.
clip_image005

Figure C
The examples in Figure C and D show the possible configuration should the specific client not be able to handle multiple data streams or if everything could be sent to the tape drive at the same time. The bottom right needs 100MB/Sec, but with only a slight compression ratio this scenario would keep clip_image007

Figure D
the tape drive streaming at an optimized rate. If the original example had each stream taking one hour, the backup window would need to be 20 hours to complete; where as the final example could finish all backups in only 1 hour.