Re: Seeking advice on Oracle disk configuration

Johnny,

   the slowest operation any computer system will do is most likely disk activity - all disks (except for solid-state) require some sort of mechanical device to move the read/write heads back and forth and the disk itself obviously has to spin. Therefore, if you have number of files on the same disk which are accessed together AND if the arrival rate of the disk transactions is also high, then the possibility of I/O requests queueing is also very high. Long I/O queues are the most common reason that I've found in applications suffering poor response times.

To get around this problem, you should spread your heavily accessed files across as many actuators as possible. This can be difficult to do if your disk subsystem appears as a single 56Gb disk. The database we're designing for a client at the moment, will need something like 330 - 380 Gb of disk for  production.
We're intending to use RAID5 (provided we can get a sub 4 second response time with 1,000 concurrent users) and have configured our raid banks in chunks of ~16  Gb
per bank. We're still fiddling with RAID5 and have fair bit of work to do  before
deciding on the eventual configuration, however I wouldn't recommend creating a  single
56Gb RAID5 disk - I would expect almost any application to run like a dog with  this
sort of disk layout. The other thing to consider is the number of RAID controllers you have available and the throughput of these (bytes per second).

Hope this is useful,

Matt Jones
DBA
CSC Australia
matjones_at_nla.gov.au

On Tue, 2 Jan 1996, Hua, Johnny (AFCN) wrote:

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>
> G'day to all, we are planning to install Oracle database and Financial and
> HRMS modules on an HP 9000 model 800 K410/4 with 1.2GB memory. The disk
> subsystem consists of a 17 x 4GB disk array unit. It has been proposed to
> configure the disk subsystem to a single Raid5 disk of 56GB with two hot
> stand-by disks. We are a bit concerned with the potential IO bottleneck to
> configure the subsystem as one disk. Would anyone out there have used a one
> single MASSIVE (56GB) disk configuration? Would IOs to the disk become a
> major bottleneck? If so, would it be better to configure the subsystem into
> 4 or 5 smaller disks?
>
> TIA for any help.
>
> Johnny Hua at FAO of the UN, Italy
>
> (johnny.hua_at_fao.org)
>
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 matjones_at_nla.gov.au      Matthew Jones
                          CSC Australia
                          Phone: +616 262 1480
                          Fax:   +616 273 2116
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