Re: INFORMIX-OnLine DSA and RAID: which level is the best?

cracraft@ix.netcom.com (Stuart Cracraft) writes: >We also had an Informix Raid 5 system (about 180GB) and >had nothing but trouble. >After changing to Raid 0+1, we have had nearly continuous >uptime and very few downtimes. >It is my opinion that Raid 5 and Informix do not mix. >--Stuart >scott@tiga.worldaccess.nl (S. Hanson) wrote: >>Melvin Perez Cedano wrote: >>> >>> Hello Informixers: >>> >>> I would like to get some opinions about your experiences using >>> INFORMIX-OnLine DSA version 7.x and RAID disks. I would like to get your >>> opinions concerning to performance and mirroring. >>> >>> This is for an OLTP application on IBM RS/6000 family. >>> >>> >>> Thanks in advance, >>> >>> >>> Melvin Perez Cedano >>> Technical Vicepresident >>> CAM Informatica, S. A. >>> >>This topic has been covered recently but here are my opinions. >>It really depends which level of RAID you are using. If you are using >>RAID 1 (mirroring) then it is no problem. >> >>If you are using RAID 5 (striping) then, in my experience, it is better >>not to use RAID 5 disks for Informix since you do not really know which >>spindle you are working with, so it is difficult to tune Informix. >> >>If you plan to use the RAID with other applications than Informix >>simultaneously, then forget it. Then heads of the disks will not stay in >>the Informix partition but will jump all over the place drastically >>reducing your performance. >> >>Another issue is that Informix can only handle chunks <= 2GB, so you >>would need to partition the RAID. Use 2GB disks for optimum performance. >>We threw out our 16GB RAID 5 box for 8x2GB mirrored disks and we now run >>about 10 times faster. >>Scott >>Scott Hanson Junior Consultant >>scott@worldaccess.nl NexTime B.V. office: (31) 10 207 5400 >>www.worldaccess.nl/~scott The Netherlands fax: (31) 10 456 9122 The above RAID 5 problems have been documented for quite a while now, and have been taken care of in the high performance RAID 7 level. M Willett Storage Computer http://www.storage.com/informix.html http://www.storage.com/uk.html http://www.storage.com/netherlands.html