From: richard@npri6.npri.com (Richard Head)
Newsgroups: comp.os.vms
Subject: Re: DEC File Optimizer for VMS
Date: 6 Sep 92 15:00:36 GMT
Distribution: world
Organization: NPRI, Alexandria VA

williamsca@hiramb.bitnet (Curtis Williams) writes:
#
#>We have installed DFG010 on our 6510 and Workstation.  Every time I have tried
#>to run it on the workstation  the drive where news items are located there are
#>several things that happen.  First, DFG goes through a file evaluation phase
#>which takes a while because there are so many files.  Next, it goes the a file
#>pre-processing phase which I have seen take 10 hours or more. At this point,it
#>goes into an RWAST state and I never see it work again.  I have also tried to
#>run it on the 6510 one time and it went into RWAST there as well.
#
#>Has anyone else had similar experiences?


The following is a re-post of my DEC File Optimizer experiences: 



			* * * * * * * * * *


Newsgroups: comp.os.vms
Subject: Re: DEC DFO - What's the "full" story?
Date: 13 Jul 92 01:34:13 GMT
Distribution: world
Organization: NPRI, Alexandria VA


I have experienced a number of caveats with DEC File Optimizer ("DFO"):

** DFO has the capability of optionally reading in user created "options"
   files that specify one or more of the following:

	o Files/Directories to be excluded from movement/defragmentation

	o Files/Directories to be considered frequently accessed, therefore
	  moved to a more optimal location on the disk for more effecient
	  disk access.

	o Files/Directories to be considered dormant, therefore moved to a
	  location on the disk (I think) would be considered less optimal,
	  since it isn't accessed much anyway.


There are at least 3 caveats with these options files:

1) You must specify the disk device name in the options file.  This is absurd,
   since the defragmentation process only works on 1 disk.  Thus, you can't
   specify [...]*.*;*, you must specify <DISKNAME>:[...]*.*;*.


2) There is the potential for abuse with the options file here.  Since it
   allows wildcarding in the filespec, an options file may specify thousands,
   or even hundreds of thousands of files to be excluded, considered frequent,
   or considered dormant.

   From what I could ascertain, DFO wants to read in the file header for each
   file it can process from the options file.  When your wild-carded file specs
   included thousands of files, the working set of the defragmenter process
   must extend to read in all of these headers.  I pressed the envelope on my
   system and a DFO process increased to over 10,000 pages.

   Since the working set extent of the DFO engine process cannot be specified
   on any command line /any startup file, the only resolution I could find at
   the time was to increase the sysgen parameter PQL_MWSEXTENT (to 12000 on my
   system).  Since extent size rarely creates a problem, this isn't serious.

3) The more stuff in the options file, the longer it will take.  Unless you
   *really* want something to be considered frequent or dormant, don't use it.
   IMHO, RAXCO's PerfectDisk approach is more sophisticated.  They use volume
   expiration to determine how frequently a file is accessed, and will place
   the file based upon user-supplied information on what the "warehouse" and
   "frequent" dates should be.  None of this reading file headers into memory
   baloney. (I think).


** Using BYPASS.  I don't recall about PerfectDisk, but DFO uses the BYPASS
   privilege with a vengeance.  Normally, this isn't a problem.  If you have
   security auditing for FILE_ACCESS=BYPASS enabled, stand by for a potential
   audit log meltdown.  Even if only a few files have their file protection
   set so that SYSTEM doesn't have Delete access, it seems like DFO wants to
   work on a file over and over and over again.  This will generate a *lot* of
   audit messages.  Either disable BYPASS auditing, or ensure all (most) files
   on the disk have S:RWED access.


After I figured this stuff out, it works ok ;-)

-- 
richard@npri6.npri.com  <Richard Head>
I've fallen and I can't reach my beer!