RAID10 config...

Hi!
I'd like to collect some thoughts on raid10 io configuration for a write-heavy system.
I've got 8 discs hanging off one controller which controls 2 SCSI buses. (9.2.0.4, RH linux) I can't have more disks nor more controllers. The controller has 64MB of battery powered cache.

I'd like to do mirroring on all files.

So, I can imagine several setups, the simplest being (IMHO)

    1 pair for OS, SW (+ 1 controlfile)
    1 pair for redos
    1 pair for archivelogs (+ 1 controlfile)     1 pair for datafiles

My current one is

    1 pair for OS, SW (+ 2 controlfiles)     1 pair for redos and archivelogs
    2 pairs for datafiles
    which I don't really like because all controlfiles     are on the same disk and ideally I'd have 3 controlfiles.

However, since the OS+SW won't create much load, I could in theory put the archivelogs there too:

    1 pair OS,SW,archivelogs (+ 2 controlfile)     1 pair redos
    2 pairs or 1 quadruple for datafiles     

Am I right in assuming that during writes, controlfiles become bottlenecks?
Would it more sense to spread out the datafiles or the redos? The lamps on my redo disks are almost constantly on during our load runs but I imagine that only small portions are written each time. The statspack says 1,804.45 per transaction, 124,352.33 per second, I suppose it's bytes. Also log file sync and log file parallel write together take up 55% of the % total elapsed time in the top 5 timed events of my statspack report. (db file parallel write are another 13%)

The problems I see are basically, how to distribute the controlfiles and how to make redo writes faster, given 8 disks.

Sorry, I forgot. Right now we've got each disk of a pair on another SCSI bus so that every access goes over two buses. I am thinking of reserving one bus for the redo disks and one bus for all the other disks. Would that make sense?

Lots of Greetings and Thanks!
Volker Received on Tue Oct 21 2003 - 11:43:32 CDT