Hi, If you can afford to do what Joerg suggested, you'll get a very powerfull system but the price is nice too. If you have low budget there are some things to consider:
- It seems better to use Software RAID under Linux than to use a cheap hardware RAID controller. If you go the hardware way you have to spend some real money to get better performance. - There are different filesystems for linux available and you may get much better performance choosing the right filesystem (XFS comes to mind). I don't know about SAPDB but I know that people are using Oracle on XFS because of performance and stability. There was a good article in german linux magazin 11/2001 about tuning Oracle 8i. Of course it's for oracle but many things are the same for sapdb. -Simon "Mensing, Joerg" schrieb: > > Hi, > > -----Original Message----- > > From: Flemming Frandsen [mailto:[EMAIL PROTECTED]] > > Sent: Dienstag, 26. Februar 2002 08:07 > > To: [EMAIL PROTECTED] > > Subject: Multible disks and performance > > > > > > Right now I have SAP DB running along with a webserver on two hardware > > mirrored SCSI disks and the performance is ok, but I would > > like to know > > what the database would be happiest with in terms of disk setup, for > > when the time comes to tune the setup for speed. > > > > The box is running Linux on a dual P3 with 1 GB of RAM. > > > > Naturally all disks ought to be mirrored and the filesystem, data and > > log ought to be on seperate disks, this means a minimum config of 6 > > disks: > > > > Files: 1 + 1 > > data : 1 + 1 > > log : 1 + 1 > absolutely fine > > > > For the filesystem mirror I think the dedicated SCSI RAID controller > > will do nicely. > > > > Now, the question is: Who is better at doing the data and log > > mirroring, > > the hardware (or OS) or sapdb? > > > Every user level software solution (including SAPDB) has to fight the > overhead of an additional > system call and an additional copy action. This fight you cannot win. The > operating system has an > advantage since the extra copy action is not needed and the system call > overhead is no problem. But > if the OS kernel has to setup two SCSI controllers, it will block the system > bus twice. Depending on > the I/O bus architecture (doubled memory transfer due to separate > controllers) and the delays during > programming SCSI controllers there is some time spend in the kernel, which > could be used otherwise... > Since mirroring is done on page based, there is no ace to play like caching > on user level. My answer > is therefore, if you can afford you should choose a hardware solution! > > The highest performance you will get from a storage array with a big cache. > This will promise you > security and performance. If it is well protected against power fail, you > can reach I/O times comparable > with a solid state disk. Some of our customers use a SAN solution > (EMC,NetApp) with up to 16GByte Cache memory > redundant power supplies and dedicated I/O processors, that do mirroring as > background jobs... Or look for > smart disk arrays (i.e. compaq), that allow to remove disks on the fly > without any reconfiguration needed. This > solution is more cost effective and just puts an extra tower into your > machine room... > > But if you do not like to spend the money on a disk array, dedicated RAID > controller cards are next > choice, as you suggested. Rule of thumb: Each devspace its own disk. As more > disks as better your > throughput. > > CU > jrg > _______________________________________________ > sapdb.general mailing list > [EMAIL PROTECTED] > http://listserv.sap.com/mailman/listinfo/sapdb.general _______________________________________________ sapdb.general mailing list [EMAIL PROTECTED] http://listserv.sap.com/mailman/listinfo/sapdb.general
