Re: Oracle Performance in Unix machine with hardware Raid 5

multiple mount points on the same RAID volume on the same controller will mean that different sections of the RAID volume have been allocated to different mount points.

If you were going to use all of the space on the RAID volume, then multiple mount points doesn't necessarily degrade performance compared with a single mount point. but it sure makes backups easier.

if you were only going to use half of the storage volue, you would want to mimize disk seeks (across tracks) and want to keep files most frequently accessed near each other, and near the outside of the physical disk surface, where transfer speeds and data density are highest (as seen by the disk head). in this case, you could create a mount point using the inner-most tracks for online backups of datafiles and other infrequently used data.

Various books cover this subject.
I was reading one called Oracle 8i Unix Performance Tuning - but its on my desk at the office.

Christopher, I believe that you were unwilling to answer the actual question - and just wanted to (understandably so) bash RAID 5. The poster appeared to me to state that they *are* using a RAID 5 configuration.

To answer his question, I would state that he should attempt to keep binaries (static) on a separate mount point from datafiles (dynamic) but attempt to keep log files, control files and data file as close together as possible so as to minimize track-to-track seeks. The most frequently accessed files should be towards the outermost tracks on the disk.

As some people here have pointed out in the past, a RAID controller with sufficiently large cache can overcome some of the penalties associated with RAID 5 parity overhead.

hth,

Paul

Christopher Spence wrote:
>
> Raid 5 will degrade performance, not many mount points.
>
> You will have contention, but that is not because of mount points or because
> of the lack of them. It is due to the fact that everything is running on
> the same set of disks.
>
> Raid 5 takes a big hit on performance, but if that is your only option, you
> need to see if write performance is suitable enough for what you are trying
> to accomplish. Although Raid 5 is very slow on write performance, it may be
> enough to accomplish what you are trying to do as it's read perfomance is
> good.
>
> "Do not criticize someone until you walked a mile in their shoes, that way
> when you criticize them, you are a mile a way and have their shoes."
>
> Christopher R. Spence
> Oracle DBA
> Phone: (978) 322-5744
> Fax: (707) 885-2275
>
> Fuelspot
> 73 Princeton Street
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>
>
> -----Original Message-----
> Sent: Friday, August 17, 2001 10:31 AM
> To: Multiple recipients of list ORACLE-L
>
> Hi Guru,
>
> We will be implementing Oracle in unix machine with Hardware Raid 5. We
> can't implement Raid 1 as we do not have sufficient disk space.
>
> Initially, we thought of having many mount points .ie. 1 mount point for
> data files, another for index files, other mount points for redo log,
> control file, archive log etc. The vendor consultant told us that having
> many mount points may degrade the system performance. Is it true ? We've
> decided to have different directories for data files, index files etc but I
> am still worry about data contention.
>
> Any advice ? Thanks.
>
> Regds,
> new bee
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