Re: Help With Disk Layout

Too many things to address, but first of all stay away from raid 5 unless you need to, use raid 10 (stripped mirrors) instead. It's not too bad if you are just reading (such as DSS), but it's rarely ever that.

System (ok but not great).
Temp, Rollback ( NO WAY) These are either even reads to writes with the lean towards writes.
Redo log (Absolutely no way, no how unless you really want to kill performance).
I have setup mine on their own disks (4 disks just for Redo's) 4 redo logs in the group

redo1 (disk1 and 2)
redo2 (disk3 and 4)
redo3 (disk1 and 2)
redo4 (disk3 and 4)

The above scenario helps due to the fact that redo's are written sequentially and read sequentially. While redo1 is being written, redo4 is being read, and when the switch is done (2 is wrote and 1 is read).

Because of the sequential reads and writes the disk heads work very efficiently as long as nothing else is on those disks.

The increase in performance is worth the wasting of the disk (1g used on each of 4-9g disks). My log write speed quadrupled. Not that this should be a good thing, but I now write a 500M redo log in less than 2 minutes during peak periods.

Now see below.

--
Robert Fazio, Oracle DBA
rfazio_at_home.com
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"Sidhe" <sidhe_at_home.net> wrote in message news:39351657.93010A42_at_home.net...


> This is my first install on a RAIDed array and I could use some

> recommendations. I am planning on

> just mirroring my transaction logs (no RAID) but I've been told to make

> sure everything else is RAID

> 5. I don't like it but we've got huge amounts of mirrored write behind

> cache so that makes up for

> some of it.


Maybe, but don't count on it.



> I know these questions are subjective but even general

> answers will be helpful to me.  Anyway here are my questions...

>

> 1. Is there a problem with putting my System and Temp tablespaces on the

> same RAID 5 set along


Don't do temp, I would suggest actually stripe and not mirror before I would
suggest raid5.  You do want to take availability into consideration, the
instance will possibly crash, but recovery is easy (no real backup needed).



> with one copy of my Control file?


Not an issue.



>

> 2. If I'm using RAID 5 then is there really any reason to keep multiple

> members of my Redo Log


I personally would say if you do use raid5 then maybe that would be ok, if
it is an autocorrecting raid5 (subdisk fails it will replace it)



> Groups?

>

> 3. I will have the Oracle app itself ($ORACLE_HOME) installed on it's

> own RAID 5 set. Is there any

> problem putting one of my control files on this drive set? How heavily

> are the $ORACLE_HOME


Not written to much, especially if your logs/dumps are written to their own
filesystems.

subdirectories really used?


>

> 4. Any further advice you may have on this subject is appreciated.

>

> Thanks in advance,

> Roger Westbrook

> Dollar General Corp

> rwestbrook_at_dollargeneral.com

> (615)855-4378