Re: Informix and RAID?
Test IT wrote: > > The folks from Informix told me that running Informix on a box in a > RAID configuration is not the best idea. They say that performance > drops. Is anyone running Informix 7.11 or > on a RAID box? We're > talking less than 100 tps and less than 20GB of data. If you > converted from not RAID to RAID, did you see a big performance drop? > > If people aren't using RAID how do they deal with fault tolerance? > Morroring? I'm about ready to go production and I'm at the point > where I need to buy a production server. I don't want to screw up > Informix, but I sure like the warm and fuzzy feeling of RAID. > > Thanks for any comments/suggestions > > Jason Fry > Washington State Legislative Service Center > fry_ja@leg.wa.gov RAID Performance 1993 vs. 1996 I've measured the speed of several RAID Systems ( AT&T, HP,... ). RAID Level 5 Systems offered in 1993 had a performance of about 1MB / 14 Seconds to 1MB / 19 Seconds. This poor performance has improved to 1MB / 1 Second to 1MB / 0.5 seconds in 1996. If the RAID 5 System uses a separate cache controller with 32-64MB cache, it would result in a very high performance. But the cache controller must have a separate battery power supply to ensure that the data in the cache can be written to disk even when the system goes down. If you know the average number of bytes that you write to disk, you could determine wether you can use a RAID 5 System or not. Simply run the following test. time dd if=/dev/l_unit of=/dev/null bs=2048 count=5000 This would read about 10MB from a logical unit of your disks. The speed for writing the same amount of data would take about 1.5 times longer. Run the above "time dd ..." command twice and compare the real time. If it's both times approximatly the same real time, than you have no cache. If the speed differs, than increase the value for the "count" parameter to find out, how many cache you have. I believe there is no need to avoid RAID 5 Systems today. Stefan. stefan@weideneder.de Fax: +49 89 3617015