Re: RAID

Brian Yan wrote in message <36198879.2E53_at_gpu.srv.ualberta.ca>...
>Hi there,
>
>I am new on DBA stuff. I read DBA Handbook by Kevin Loney. It says that
>some database file should be at the different disks. My questions are:
>
>1). Does the 'different disks' here mean the different PHYSICAL disks?

It means different *physical disks*.

>or just different logical volumes? Our company's old database put
>different database file in different logical volumes (not necessarily
>the different physical disks), I am wondering if that violates the OFA
>rules?

Well, OFA really deals with 'mount points', but of course the assumption is that those mount points (/u01, /u01, etc) are pointing to different disks. If they are not and you lose a disk, it could be Goodbye Database. :-) And of course you also have to think about performance.

>
>2). My first thought of above question was 'physical disks'. It makes
>sense to me that if the two different tablespaces are at two different
>physical disks, the RW heads of two disks won't interfere each other, so
>the performance is improved. However, is this still true for RAID disks?

Which RAID level? You need to read up a bit on RAID.

>
>For example, I have five RAID5 hard disks u1~u5. I create DATA
>tablespace in u1, INDEX tablespace in u2. However, when data in DATA are
>stored into hard drive, it will be striped into different drives
>according to RAID. Same thing happens to INDEX data. In this case, won't
>the data in DATA and data in INDEX be mixed up? How can we dedicate the
>whole disk to DATA tablespace under RAID environment?

Set up multiple RAID sets. And then make sure the mount points are pointing to these sets (i.e., mapped to different hdisks (logical disks - which is how the RAIDed drives will appear to the OS)). Same thing is true if you use raw devices - make sure the raw partitions (lv's) sit on different RAID sets. Depending on your RAID controller and the RAID levels you choose, you may or may not be able to set up multiple RAID sets with it. If not, you'll have to buy multiple adapters - which you might want anyway to balance I/O.

>
>Thank you in advance! Have a nice day (night).

You too. :-)

>
>Brian Yan

MotoX. Received on Tue Oct 06 1998 - 00:00:00 CDT