Free space effect on performance

[Benjamin Cheong]

Hi,

I'm currently trying to size a database and I'm wondering how much the amount of free space I have available on my disk affects the application performance. Does it have much performance impact?

Any rules of thumb for how much free disk space to leave?

Thanks in advance!

Cheers,
Ben

P.S. This thread has been moved from Disk to HP-UX > databases. -HP Forum Moderator

[Uwe Zessin]

Many, many years ago a company named Digital offerend a HI-SPEED mode on some of its disk drives. It did that be reducing the capacity at the disk level which resulted in shorter seek distances. You traded capacity against speed.

I have heard other examples of companies who tried to allocate their files on the outer cylinders of the disk drives only, because the speed is higher there.

With all the abstraction layers in todays storage controllers I have doubts that these techniques are still working.

[Mobeen_1 · Accepted solution]

Ben,
It really depends on what type of database volumes you are creating (Unix filesystem or raw) and also how thes database volumes are spread over.

I personally think that the amount of free space doesn't play much. How ever, the most important things to be considered are

1. When you create a Database volume,
make sure that you spread it across
physical volumes

2. Try not to keep the database's data
volume and log volume on the same
devices.

Item#1 above is a good practise from performance point of view and item#2 is a good practise from disaster recovery point of view.

regards
Mobeen

[Shaikh Imran]

Hi,
There is no such concept that free space impacts the performance as far as database is concerned.
If matters only in O.S an that too it needs to be configured as swap that's all but Database side it has no impact on the performance.

Regs,