Cluster size of large disks

[Gerry Downey]

Hello everyone,
I am installing a 36GB disk in an Alpha 800 running VMS 7.1. The minimum cluster size that I can set on the disk is 69, however I need a maximum cluster size of 51 due to application restrictions.

Is there any way I can set a lower cluster size? Can the disk be "partitioned" to allow it?

Or if I upgraded VMS will this allow me to set a lower cluster size?

Thanks,
Gerry

[Ian Miller.]

what application restriction prevents the large cluster size?

The changing allowing smaller cluster sizes was in VMS V7.2 along with lots of other good stuff so upgrade if you can to V7.3-2 or V8.2

You could use the LD driver to create smaller disks from container files on the 36Gb disk.

[Aaron Lewis_1]

Gerry, I don't remeber exactly when these 'INIT' switches bacame available, but there is:

/limit -- defaults to cluster size of 8 &
allows you to dynamically expand
the size

/cluster -- allows you to specify a smaller
cluster size

/structure=5 -- specifies and ODS5 disk,
instead of ODS2. provides
for upper & lower case file
names, support for long
file names and a few other
nifty tricks. Default
cluster size is 3

All of these are in VMS 7.3-2, so an upgrade of VMS will get you what you need if 7.1 doesn't support them.

[Gerry Downey]

The application is a third party application that uses RMS and I've been told that the cluster size must be 51 or lower.

I tried init/cluster, but it wont let me set it lower than 69.

Looks like a VMS upgrade.

Thanks for the replies,
Gerry

[Antoniov.]

Gerry,
I'm afraid you cannot use value less than 69. If you read carefully help /cluster you can read minimal value of cluster is:
(disk size in number of blocks)/(255 * 4096)
With 36Gb HD the minimal value is 69.
So you have one these alternative:
1) Mount a 36Gb HD
2) Upgrdade you VMS 7.3 and use ODS-2 disk.

Antonio Vigliotti

[Uwe Zessin]

Earliest release that supports the larger allocation bitmap (but not dynamic volume expansion) was V7.2. Before that, BITMAP.SYS was limited to about 1 million bits (255 blocks * 512 bytes per block * 8 bits per byte).

In case you're curious:
from the formula that Antonio has mentioned:
4096 = 512 bytes per block * 8 bits per byte

[Hein van den Heuvel]

As the others wrote: Upgrade this is deriable anyway and now you have a good 'excuse'.
Or you could use the LDdriver to partition.

>> The application is a third party application that uses RMS and I've been told that the cluster size must be 51 or lower.

Intersting. That 51 happens to be the number used by Vir for a relative file multi-block-count in an other recent thread:
http://forums1.itrc.hp.com/service/forums/questionanswer.do?threadId=946349

Please question that 51 max !
Where does it come from?
What is the (suspected) problem with anything larger?

From a pure RMS perspective it makes absolutely no sense at all.
The clustersize is (should be :-) entirely transparant to RMS record IO applications.
The only obvious direct effect from cluster size is the (obvious) round up during allocations... but that is transparent.
It will also change the EDIT/FDL/NOINTERACTIVE tuning rules, but those effects are minor, and can be over-ruled by hardcoding a selected clustersize in the input analyze data file.

Please do NOT accept this 51 line at face value. Check into this. It may well turn out to be antiqueted bagage which should be thrown out. If it is really true, then please explain because we'd love to learn and we may be able to fix or give alternatives.

hth,
Hein.

[Ian McKerracher_1]

Hein seems to be particularly intrigued by this cluster size value of 51. Have a look at this question from last year. It may or may not be of interest.

http://h71000.www7.hp.com/wizard/wiz_9545.html


Ian

[Hein van den Heuvel]

Ian wrote "Hein seems to be particularly intrigued by this cluster size value of 51"

Not me! I am a firm believer in nice, big cluster sizes with larger powers of 2 in there. For example: 240, 256, 512, 600, or 720 or some such high number where acceptable. (thousands of files, mot millions).

But indeed, that wizard question from march 2004 also appears to have been submitted Gerry! (I peeked behind the curtain).

Hein.

[John Gillings]

Gerry,

Well, I'm particularly intrigued by this:

>The application is a third party
>application that uses RMS and I've
>been told that the cluster size must
>be 51 or lower.

I'm wondering HOW anyone could write an application that cares about the cluster size. Short of calling SYS$GETDVI to check, I can't imagine how any application would be aware of cluster size for a particular file, much less care about it!

Yes you should upgrade to at least a supported version of OpenVMS (currently at least V7.3-2), and yes, that would give you much more flexibility in configuring and managing disk volumes, BUT it shouldn't be necessary.