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Kernel setting for file reading

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Kaps_2
Regular Advisor

Kernel setting for file reading

Is there any kernel setting that will affect file reading in HP box?
7 REPLIES
James R. Ferguson
Acclaimed Contributor

Re: Kernel setting for file reading

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...
Kaps_2
Regular Advisor

Re: Kernel setting for file reading

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


James R. Ferguson
Acclaimed Contributor

Re: Kernel setting for file reading

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...
Kaps_2
Regular Advisor

Re: Kernel setting for file reading

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
James R. Ferguson
Acclaimed Contributor
Solution

Re: Kernel setting for file reading

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...
Kaps_2
Regular Advisor

Re: Kernel setting for file reading

Oh I missed that. Any ways thanks
Hein van den Heuvel
Honored Contributor

Re: Kernel setting for file reading

>> 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