Re: What's VxFS buffer size ?

Hi

You can tune the veritas I/O and memnory parameters by adding lines to /ect/system. I agree with Zhenming that you can size it when you create the file system just as an NFS file system can be.

Also be aware that the low level OS read still plays a part. on solaris i think its 128K but i may be wrong, therefore setting multiblock_read_count needs to take this into accouint as well.

I have a four page document faxed to me from veritas about a year ago about tuning parameters . Its called "Modifying Tunables", see if they can send you an up to date copy. I dont have an electronic version. If you are stuck i could fax my copy to you next week from the office.

Also are you aware that you can turn off the unix file cache using veritas parameters in vfstab. the one i used to get about a 20% improvement in a heavy loading program written in PL/SQL and operating against a 220 million row table is "convosynch=direct". see the alomari book on tuning oracle 8i and unix. He has a good chapter on veritas tuning.

cheers

Pete Finnigan
www.pentest-limited.com

In article <58L97.21817$Q13.2212058_at_news20.bellglobal.com>, Zhenming Wang <zmwang_at_sympatico.ca> writes
>8K block size is the default, when you create a new file system by using
>newfs, you can specify the size differently.
>
>Zhenming
>
>Bass Chorng wrote in message ...
>>In Steve Adam's article of "Why a Large Database Block Size", he
>>points out that all Unix file system buffer size are invariably 8K.
>>
>>Does anybody know what VxFS default buffer size is ? Is it tuneable ?
>>How large can it go ? How do you verify it ? And how do you change it
>>?
>>
>>The other question is, if I can beef it up , do I still benefit from
>>raw on my datafiles ? I am talking about a database that's not write
>>intensive at all.
>>
>>I tested our system (VxFS, no QIO) with full table scan in very large
>>db_file_multiblock_read_count and examine the trace file. The blocks
>>that Oracle is reading per IO is maxed at 256K. So I know for sure
>>VxFS is not
>>operating at the same 8K buffer size like ufs.
>>
>>Thanks for any knowledge sharing in advance.
>>
>>-Bass Chorng
>
>
 

-- 
Pete Finnigan