How do I use raw devices?

I am running ORACLE 7.0.15.4 on a SparcServer 1000, running Solaris 2.3. I am beginning to look into using raw devices, and wondered if anyone has any advice for me.

The two reasons why I'd like to use them are:

1. To decrease the annoying 20% space overhead that seems to come with formating a drive and putting a file system on it.
2. To increase I/O performance.

My questions are:

1. Do you make all partitions the same size?

   One of the things that worries be about raw partitions is how difficult it    seems that it will be to balance I/O. So, I'd like use partitions that are    all the same size, as recommended in the ORACLE installation guide.

   However, the tablespace files will vary in size, so the partitions will need    to accomodate that. What does it do to performance, etc., if you allocate    400m to a tablespace using 8 50m files?

2. How many partitions can you have on a disk?

   We can have many instances on our machines, and many applications, which    we typically put into separate tablespaces. This means a reasonable number    of files, and an even larger number of partitions, assuming that I have    created relatively small partitions. However, my disks are 1 or 2 gigabytes    in size, so if I could only create a small number of partitions, say, 10,    each partition would be 100 or 200 megabytes, which would be way too much    for some files.

3. Do you mix raw partitions and regular file systems?

   If there is a limititation on the number of partitions on a disk, one    way to deal with that is to only use raw partitions for the really big    stuff.

4. What utilities do you use to copy, backup, and restore the data files on

   the raw partitions? We have a large amount of data, so I'd like to find    a utility to do the backup that supports writing to multiple tapes.

Thanks,

Bob

-- 
Bob Swisshelm                | swisshelm_at_Lilly.com     | 317 276 5472
Eli Lilly and Company        | Lilly Corporate Center  | Indianapolis, IN 46285