From:	SMTP%"RELAY-INFO-VAX@CRVAX.SRI.COM"  5-AUG-1994 12:50:36.83
To:	EVERHART
CC:	
Subj:	Re: Virtual disc file layout

From: vandenheuvel@eps.enet.dec.com (Hein RMS van den Heuvel)
X-Newsgroups: comp.os.vms
Subject: Re: Virtual disc file layout
Date: 5 AUG 94 00:57:40
Organization: Digital Equipment Corporation
Lines: 30
Message-ID: <31sh1f$n3o@jac.zko.dec.com>
NNTP-Posting-Host: EPSYS
To: Info-VAX@CRVAX.SRI.COM
X-Gateway-Source-Info: USENET


In article <20200487_005ACC60.0098275A7EB5C000$12_1@UK.AC.RHBNC.VAX>, CHAA009@VAX.RHBNC.AC.UK writes...
>I'm using Glenn Everhart's VDDRIVER to divide up some discs (including a 9GB),
>with the whole physical disc space used by virtual disc container files.
>I have been using a setup of the /INDEX=BEGINNING and the container files
>arranged in descending order of size.
> 
>I wonder whether there is a more efficient layout.  For instance, assuming that
>the virtual discs are equally loaded, should the physical disc's index file be
>in the middle, with the container files each side ?  In this case, should the
>virtual discs' index files be at the end nearest the physical disc's index
>file ?   Does it actually make any difference where they are ?

I should not think that the physical disks index file will be used at all!
Just move it out of the way like you did! Also, you might as well grab a
nicely big clsuter size for the physical disk ( 200? 1000? no more than 1024!)

> 
>Is there an easy way to specify the position of a file ?  

Ayup, through an RMS Allocation XAB. The easiest way to get there
without porgramming is through FDL:

$create/fdl=sys$input tmp.tmp
area 0; alloc 100; contiguous yes; position logical 591966; exact yes

Hope this helps,               +--------------------------------------+
                               | All opinions expressed are mine, and |
Hein van den Heuvel            | may not reflect those of my employer |
vandenheuvel@eps.enet.dec.com  +--------------------------------------+