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

[Richard B. Gilbert]

On 2/5/2011 1:02 PM, Phillip Helbig---undress to reply wrote:
> 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?
>

The last time I looked, 40 GB was the smallest capacity disk available 
new and that was a while ago.  I've seen 300 GB disks advertised.  As my 
own storage needs are quite modest, I haven't paid a great deal of 
attention to the disk market.