[Info-vax] what is a good value for /CLUSTER_SIZE? (INITIALIZE and qualifiers)

[Phillip Helbig---undress to reply]

HELP/INIT/LIMIT says:

        If you specify /LIMIT and do not specify a value for
        /CLUSTER_SIZE, a value of /CLUSTER_SIZE=8 is used.

while HELP INIT/CLUS says:

     Disks that are larger than
     50,000 have a default of either 3 or the result of the following
     formula, whichever is greater:

     (disk size in number of blocks)/(255 * 4096)

Up until now, I have usually taken the defaults of INITIALIZE, except
where something else (e.g. /SYSTEM) was absolutely necessary (and, of
course, I specify /HEADERS as much larger than the default; I use 50,000
per GB as a rule of thumb).  For a 9-GB disk, this results in a cluster
size of 17.  Since I plan to do some stuff with DDS and DVE soon, I need
to specify /LIMIT.  This will give me a cluster size of 8 unless I
specify something else. 

Should I stick with the default implied by /LIMIT, i.e. a cluster size 
of 8, or go with the default cluster size (17 for a 9-GB disk), meaning 
I will have to specify it if I specify /LIMIT?

50,000 per GB is on average 20 kB per file, but 50,000 is on the safe
side; my typical file size is closer to 50 kB.  The default cluster size
of 17 blocks is somewhat less than 9 kB, significantly smaller than the 
average file size.  Thus, my gut feeling would be to go with 17 for a 
9-GB disk, and in general the default cluster size one would get without 
/LIMIT, rather than the 8 which /LIMIT has as default.

On the other hand, considering that most disks these days (and even when
/LIMIT was introduced) are probably larger than 9 GB, this means the
default of 8 used by /LIMIT is usually significantly smaller than what
the default cluster size otherwise would be.  Is there a reason for
this?  More generally, why introduce a new default with /LIMIT at all?