Re: Mail to Dusan Bolek

Samuel Tran <stran_at_immostreet.com> wrote in message news:<3B86206F.B3B1933C_at_immostreet.com>...
> Hello Dusan,
>
> Thank you for your answer to my post in comp.database.oracle.server.
>
> Please may I ask you a few questions about Oracle file placement as you
> are a real Oracle GURU ?

Wov, a good joke. :-)

> If you have to build a new Oracle 8i server, what would be exactly the
> hardware specifications of your machine (number of disks, RAID 1, 5
> or 10, ... ?) and what would be your file placement ?

It's very difficult to tell, because it depends on lot factors.

First factor is of course money. If you know how many can you spend, then you can choice a platform. Unix or NT. Then you should buy the biggest box available for that prize. I think that is a good idea to buy not fully equipped box. For example, If you know that you need two CPUs, then you should buy a box which can be upgrade to four CPU, because you never know what you will need in future and is better to buy two CPUs than new server. Your server should has as many drive bays as possible, because with Oracle you can easily run out of them. Of course another way is an external disk storage, but that's usually more expensive solution. When you know your server, you can count drive slots and start to plan your Oracle storage.

Example - smaller database:
If you have 7+ drives, then you should use mirroring. With seven disk you can use this configuration:

Disk 1+2    System + ORA INST 18 gigs drives are usually enough
Disk 3+4    SYSTEM tablespace, USER_DATA tbl, RBS
Disk 4+6    INDEX, TEMP tbls
Disk 7      redologs

With this layout you can have pretty good perfomance and availability. Oracle datafiles and system should be on mirrored disks, because if you must recover database from tapes when one of your disks malfunctioned, then your availability will be without mirroring poor. If you have mirrored disks and one became unusable, then you just call your HW vendor and within few hours you have a spare one, you can plug this new disk and your users didn't notice that something went wrong. Of course you can tell them, what disaster you encounter and solve to improve your image. :-)
Without mirroring your users can't work for several hours and they will blame you.

> You said that RAID 5 is not a good choice because of slow performance.
> Actually RAID 5 is slow for write access.
> Yet some people recommend it for database installation ...

Personally I do not like system which automatically adjust critical parameters without my intervention. Especially with Microsoft SW that's very common.I like to setup as many things as possible. Definitely it cost more time, but usually result is better. When I work with Oracle, I want to exactly know when a table is stored, or even when partition is stored. When using RAID5, I can't know it. I can't even avoid storing index on the same disk as appropriate table is and that can't be a real perfomance issue. So I'm not a big fan of using RAID5 on database server.

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Dusan Bolek, Ing.
Oracle team leader