Vinum RAID5 speed question

[Martin Brecher]

Hi, -

I plan on setting up a vinum RAID5 array of three 120GB IDE disks. The 
disks will be attached to two Promise 100 TX2 controllers, on which two 
other disks are residing, too.

The following questions have come to my mind:

1. I thought about getting disks with 8MB cache. Does the bigger cache 
size affect performance in a RAID5 scenario?

2. Currently I'm running a RAID5 with 4 older 5400rpm disks in that 
machine, and write speeds are around 3MB/s. I guess that several people 
here are running vinum RAID5 with current IDE disks, so what throughput 
can I expect from the new planned setup?

3. The volume is meant for storing all kinds of files with all kinds of 
sizes. My current setup has a blocksize of 489kb. From other people's 
experience, what blocksize might bring the best results for such general 
purpose?

4. Any other advice would be welcome, of course. :-)

Thanks,
Martin