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Conference decwet::advfs_support

Title:AdvFS Support/Info/Questions Notefile
Notice:note 187 is Freq Asked Questions;note 7 is support policy
Moderator:DECWET::DADDAMIO
Created:Wed Jun 02 1993
Last Modified:Fri Jun 06 1997
Last Successful Update:Fri Jun 06 1997
Number of topics:1077
Total number of notes:4417

1012.0. "Some ADvfs concept questions ?" by HGOVC::SIUKEUNGLEE () Tue Mar 04 1997 04:02

    Hi,
    
    Could someone can explain to me what is Cmode uses for ? What are the
    differnet if I turn off the Cmode ? Also, how to determine how many 
    log page does I need for my new file domain ?
    
    Does Rblks /Wblks same as stripe width ? 
    
    Wellcome nay suggestion!
    
    David Lee.
T.RTitleUserPersonal
Name		DateLines
1012.1SMURF::SCOTTTue Mar 04 1997 09:2713
1. The "cmode" displayed from the chvol(8) command enables/disables I/O
consolidation.  If consolidation is enabled, then at the time I/O buffers
are moved onto the device queue, the system will check to see if
sequential buffers represent I/O to consecutive blocks on disk, and if so,
it will perform a single I/O request for the set of sequential buffers
with consecutive blocks (assuming same direction I/O).  The bottom line is
that this improves performance; I'm not aware of any situation in which
you would wish to disable this consolidation. 

2. The rblks/wblks values displayed from chvol(8) are independent of the 
advfs file stripe width.

larry
1012.2No. of log page problem ?HGOVC::SIUKEUNGLEETue Mar 04 1997 10:2410
    Hi Larry,
    
    Thank for your clarify first. But I still have one more question
    about the no. of log page. How can I determine how many no. of log 
    page we need to have on my file domain ? 
    
    Thank!
    
    David.
1012.3SMURF::SCOTTTue Mar 04 1997 14:2712
You need a minimum of 512 log pages. 

The question as to what is the optimal number of log pages with respect to
performance and space utilization is not so simple.  I expect it to be
some function based on the frequency of logged operations your system
performs, the frequecy of I/O requests your system performs, and the
specific logflush operations performed (probably other factors as well). 
All that said, the expectation is that the frequency of logged operations
is typically small enough so that the number of log pages is not likely to
represent a bottleneck. 

larry