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Re: RAID

From: Jason Williams <williamj_at_mincom.com>
Date: 1998/10/06
Message-ID: <01bdf0e9$0f119a60$3b3e11ac@williamj.mincom.oz.au>#1/1

Hi,

I know a little about databases and RAID. But I not up on all the techo lingo.

> 1). Does the 'different disks' here mean the 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?

Different Physical Disks would be my likely conclusion. The reason as you have probably guessed is speed. If two different databases have to fight for the same disk heads then it is going to reduce 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?

It depends on the type of RAID you are talking about......

>
> 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?
>

You can't that's the point to RAID 5 - Redundancy not performance. On some systems you can increase access time by putting the "tablespace" on the inner tracks of the disk.

If your looking for performance above what you already have with RAID 5 - use a lower level of RAID like 0.

> Thank you in advance! Have a nice day (night).
>
> Brian Yan
>
  Received on Tue Oct 06 1998 - 00:00:00 CDT

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