Both, Raid levels 5 and 10 (striping after mirroring), have pretty good read-performance. Raid 5 read performance is better than raid 10 read performance.
However, typically most of the data you access is cached in memory, especially if you have huge amounts of memory and do OLTP instead of Data Warehousing. In this scenario write performance of disks becomes important (Transaction Log etc.). Write performance of Raid 10 is better than write performance of Raid 5. The problem with Raid 10 is that it has high cost in terms of money, since you can use only half of the capacity of the HDs. Another point is: use as many disks as possible to parallelize the I/O. Oracle (v. 8) for example uses 22 (!) Harddisks in an optimal Installation scenario confirming to OFA (Oracle Flexible Architecture for a growing database). There are cases where read performance is the only thing you care about: Data Warehousing for example. Complex Querys that nearly don't do much inserts or updates but have to read many tables/indexes that are probably not all in the in-memory cache. I also would consider to buy Sun Hardware and use Solaris instead of Intel/Linux if you have the budget, since that architecture scales much better than Intel. cheers, Detlef ----- Original Message ----- From: "D�hr, Markus Hermeskeil" <[EMAIL PROTECTED]> To: "'Detlef Schulze'" <[EMAIL PROTECTED]>; <[EMAIL PROTECTED]> Sent: Thursday, March 27, 2003 11:42 AM Subject: RE: Can SAPDB handle databases up to 500 GB and which hardware is required? > > Never use Raid Level 5 for a database server. Level 5 gives you bad > performance. Use Level 10 instead (striped mirror) if you want to use a > Raid. > > Can you clear up why you think that RAID-5 gives bad performance? > > > Thanx! > > -- > Markus Doehr SIEGENIA-AUBI KG > CCC - SAP R/3 Basis, SAPDB-DBA Zum Grafenwald > fon: +49 6503 917 152 D-54411 Hermeskeil > fax: +49 6503 917 190 http://www.siegenia-aubi.com > _______________________________________________ sapdb.general mailing list [EMAIL PROTECTED] http://listserv.sap.com/mailman/listinfo/sapdb.general
