topic Re: Kernel setting for file reading in Operating System - HP-UX

Kernel setting for file reading

Kaps_2 — Mon, 14 Sep 2009 13:24:06 GMT

Is there any kernel setting that will affect file reading in HP box?

Re: Kernel setting for file reading

James R. Ferguson — Mon, 14 Sep 2009 13:30:46 GMT

Hi:

The "buffer cache" prior to 11.31 or the "file cache" at 11.31 and after, control the caching of buffers in memory. This can affect performance in positive and negative ways.

For < 11.31 :

dbc_min_pct
dbc_max_pct

http://docs.hp.com/en/B3921-60631/dbc_max_pct.5.html

For >= 11.31:

filecache_min
filecache_max

http://docs.hp.com/en/B2355-60130/filecache_max.5.html

Regards!

...JRF...

Re: Kernel setting for file reading

Kaps_2 — Mon, 14 Sep 2009 14:30:05 GMT

Can this result in any server crash if I change the existing settings

From:

fcache_seqlimit_file 100 Default Immed
filecache_max 8160395264 Default Auto
filecache_min 816037888 Default Auto

To:

fcache_seqlimit_file 100 Default Immed

filecache_max 16325509120 Default Auto

filecache_min 1632550912 Default Auto

Re: Kernel setting for file reading

James R. Ferguson — Mon, 14 Sep 2009 14:52:40 GMT

Hi:

> Can this result in any server crash if I change the existing settings

I doubt it. Follow the guidelines for these parameters as delineated in their respective manpages.

Regards!

...JRF...

Re: Kernel setting for file reading

Kaps_2 — Mon, 14 Sep 2009 15:04:41 GMT

Cauz my existing values are 8GB -- 8160395264

& I am planning it to increase it to 16FB -- 16325509120.

And the RAM on this server is 16GB

Re: Kernel setting for file reading

James R. Ferguson — Mon, 14 Sep 2009 15:14:09 GMT

HI (again):

> Cauz my existing values are 8GB -- 8160395264
& I am planning it to increase it to 16FB -- 16325509120. And the RAM on this server is 16GB

Did you READ the manpages as I suggested?

http://docs.hp.com/en/B2355-60130/filecache_max.5.html
http://docs.hp.com/en/B2355-60130/fcache_seqlimit_file.5.html

...JRF...

Re: Kernel setting for file reading

Kaps_2 — Mon, 14 Sep 2009 15:25:44 GMT

Oh I missed that. Any ways thanks

Re: Kernel setting for file reading

Hein van den Heuvel — Mon, 14 Sep 2009 15:57:44 GMT

>> Oh I missed that. Any ways thanks

Say thanks with points!
http://forums13.itrc.hp.com/service/forums/helptips.do?#28

>> I am planning it to increase it to 16FB -- 16325509120.
>> And the RAM on this server is 16GB

That's unlikely to be right.
I am all for, more so than most readers here, to have a large max, but very few applications can justify more then 50%.

If you want better help, you may want to specify
- why do you think you need to change anything in the first place. What indicators ?!
- what are the speeds and feeds? How many MB/sec it the theoretical max (spindles, cables, hba) and what do you actually see
- reference tests, if any (cp, dd, ...)
- Brief usage description (single process, single file? Degree of parallelism? long sequential scans, or short random reads?
- Database in play (Oracle?)

Hth,
Hein van den Heuvel