In search of document(s) regarding filesystem performance

[Patrol]

I am looking for documents of any kind, which comapres the performance of the different types of filesystems, when used space come close to their capacity limits, i.e., 98-99% range, and more specifically when these filesystems house the large oracle database files.

I know there are many variables in my question but a google search did not yield any information. There used to be problems in the past with performance degraditions when the filesystems came close to their limits, but this was decade ago and I can not find neither those studies nor anything new.

Any help is greatly appreciated.

[Hein van den Heuvel]

I don't have a pointer to a document, but I do have some thoughts.

- Picking the files system is done when the disk is empty. To plan for how that file system react when it would get full seems a little silly. How about planning for it not to get too full. That would appear to be more productive.

- One problem with near full disks, in ahighly fluctuating environment is that the remaining free space is likely to be very fragmented, making it hard to find enough space for a new large file, and making that new large file very fragmented causing increases in seek times and making read-
aheads (Oracle Multy-block Read) futile.

Also, a near full disk makes defragmentation nearly impossible.


- A second potential performance problem with full disks is that there is data literally all over the disk making the seek range worst case. Of course many controller based storage setups (EVA, XP,..) decouple the linear range of blocks on logical unit from the underlying physical disk blocks used making this max seek range possibly less of an issue.

- All the above is (much) less of a problem, for Oracle applications with large, pre-allocated tablespace files.
Even for auto-extent, since there are few or no deletes, the fragmentation issues will be minimal.

In all, I would not worry too much about a file system holding large oracle files getting full. I'd sooner worry about wether using a file system, or going raw!?

Hope this helps,

Hein van den Heuvel (at gmail dot com )
HvdH Performance Consulting

[Steven E. Protter]

Shalom,

I don't know of any documents.

Oracle metalink probably has a few and as I recall, they recommend free space of 20% or so.
Your database needs the ability to cut new extents or it could stop working, quite suddenly.

My google search yielded a number of documents on how to resize the filesystem bigger online. I'd take that in itself as an ominous sign.

SEP