Re: Please recommend a disk configuration for the server

> The server has two FAST+WIDE SCSI adaptec controllers (bus
> mastering). Controller #1 has two 9GB disks attached to it.

The Adaptec controllers themselves are good and probably do not need to be replaced (in other words, don't rush out and buy a 2940UW just because you think you're going to get better performance -- you won't).

> Disk 1 is logically partitioned into drive C+D, disk 2 is
> drive E. Controller #2 also has two 9GB disks attached to it
> which are mirrors of drive C,D & E. The mirroring is taken care
> of by Windows NT. There is also a CD-ROM driver attached to
> controller #1 but the CD is rarely used---only when installing.

Mirroring done by NT is a bad idea. Stuff like that ought to be done in hardware.  

> 1. Add two more controllers to the system (we will end up with total
> of four controllers then---we don't even know if it's possible) and
> move two main drives to controller 1&2 and the mirroring disks to
> controller 3&4. This way each disk has it's own controller and,
> hopefully, the peformance will go up.

The bandwidth to each disk is not the issue here; each drive probably only puts out no more than 5-7mb/sec at the best of times, 3-4mb/sec on average, and maybe even less with the database you are running.

Even a fast wide PCI controller is adequate bandwidth wise, and there is no need to be adding additional controllers.

9 gigabyte drives really are too large for a database system though if it is heavily used; I would suggest that you not buy drives which are so large in the future, and use more drives to achieve the same capacity.

 > 2. Leave the current controllers and add a RAID controller to the
> server. Move existing drives to the new RAID controller. Say good
> bye to mirroring and let RAID worry about parallelism and distribution
> of files accross different drives.

A RAID controlelr is your best option; you really shouldn't be getting the OS (NT) to be doing what should be a function of the hardware (mirroring). That just imposes additional load on the system.

My hunch is that 9 gig drives might be too large for your specific configuration as well. However, without knowing specifics about the loading/size/usage patterns of your database, I really can't comment further. All I know is that I would never configure an moderately to heavily used oracle machine with 9 gig drives.  

> The question: which of the above will yield in maximum performance
> gain? The cost is an issue as well. If one solution only has about
> 10-15% advantage on the other, we will rather go with the cheaper
> one. As it stands right now, #1 (adding two more controllers) is
> about one third the cost of #2 (RAID).

You are going to need RAID one of these days; by procastinating now, you are just looking for more problems in the future. RAID controllers, properly configured, have a dramatic effect on the performance. Adding additional non-RAID SCSI controllers is an almost useless move since your present controllers aren't even being used to anything near their full capacity.

You might also want to look into replacing those 9 gig drives with pairs of 4.5gig drives as well, in addition to the RAID controller. This does come at a significant expense though (why 9 gig drives were used in the first place in a performance-sensitive application is a mystery to me though). Received on Sun Oct 04 1998 - 00:00:00 CDT