Oracle 9i Rel2(9.0.2.0.1) raw disk or filesystem.

[Jon Mattatall]

All DB servers 11.00.

We use some 8.0.5, a lot of 8.1.6, and are moving to 9.2.0.3. All use filesystems.

As far as I can tell, the choice was never based on performance. We have a lot of small instances (~15 per server) and it's just much easier to have filesystems so that we and the DBA's don't get things confused.

We're moving to 9.2.0.3 on AIX5.2, and again, it's planned to use filesystems. The probable reason? Inertia. We have nothing empirical to show superiority.

...and if the Series winds up Marlins-Yankees, I'd rather watch bowling.

[Steven E. Protter]

I'll keep handing out points, so long as you keep posting good data. I'm glad I created this thread, even if it did the cubbies no good.

Thanks for your posts so far.

A. Clay Stephenson: You're not a whacko, you are clearly in my opinion the most respected member of itrc. That is not a points measurement, its a subjective opinion. I appreciated the fact that you took the time to measure the data and now regret I didn't bump your score up to bunny.

I hope you come to Chicago next year.


SEP

[Stefan Farrelly]

No Clay - your not the only one who measures the performance, just that SEP never asked about performance in the original question so nobody mentioned it in their reply until you.

Any talk about using the mincache=direct etc. mount options to allow 'pseudo' raw i/o performance is a long discussion - needless to say you will NOT get the same performance as using raw i/o. There are lots of rules which must be obeyed to gain the benefit, and not all applications are written to do so (eg. i/o's on certain block size boundries). We estimated the performance benefit from this to only be <10% - which wasnt worth the effort to get it to work.

As for raw i/o being faster, of course it is, any raw dd will show its 100% faster than a dd on a filesystem, but nowadays with 2Gigabit fibres and storage systems running at 250MB/s you simply dont need to add all the complications of using raw i/o over using much simpler filesystems - which can be boosted with large buffer or SGA caches.

As youve pointed out, raw or mincache options only add a few % improvement - for a lot of effort. There are much easier and simpler ways to boost performance by changing to 2Gb fibre or add faster disks or boost your cache sizes or simply by striping your filesystem.

[Steven E. Protter]

Stefan,

You are also one of the most highly respected members here(My opinion again).


Thanks for all your input. The more the merrier. Even as this thread turns in different directions I lean more.

Thats what its about.

SEP

[Stan_17]

Steven,

We have few databases in raw via veritas quickio and some in cooked filesystem (all in 8.1.7.4)

Using cooked vs. raw IMHO, totally depends on the application you run with. If you have a busy oltp environment, then i would definitely go with raw for redologs at least to start with, as it normally suffers from partial block writes and you could also see log file sync waits followed by log file parallel write, log buffer space waits all alluding to scalability issues. so it's better to have the redolog on raw fs to get the benefits of direct/io as well as kaio.

In a typical DSS environment, tempfiles and datafiles are potential candidate for raw as most queries are unique there, which means lots of PIO's and raw is better with large io operations.

I've seen in most cases, with a well tuned apps and raw fs, performance go sky high. conversely, it could get worse if apps are bad. so the big bucks lies on tuning the apps first and then the fs.

If you are dubious about performance of the apps, then start with a fs supporting direct/io and threaded aio. see how it goes, tuned the apps and then contemplate moving into raw fs.

-
hth,
Stan

[Robert James Hanrahan]

hi all,

So far it looks that the use of RAW devices is
no longer used for ease of management of File System devices.

As regards HP/UX 11.x, do I have to configure the disks in this way for the DB datafiles?:

/etc/fstab

ioerror=mwdisable,mincache=direct,log,convosync=direct,dev=1082dc2

What about putting only the REDOLOGS on RAW?

rjh

[Steven E. Protter]

If you want to ask a new question, start a new thread please.

SEP

[Steven E. Protter]

Closed.