topic Re: OpenVMS BACKUP saveset max size ? in Operating System - OpenVMS

OpenVMS BACKUP saveset max size ?

peterfra — Tue, 21 Nov 2006 06:29:24 GMT

Hi,

what is the max size of a saveset file under
v7.3-2 (and v8.3) ? Can I do a "backup/image"
operation on a 400GB disk ?

Thanks in advance !

br, peterfra

Re: OpenVMS BACKUP saveset max size ?

peterfra — Tue, 21 Nov 2006 06:35:07 GMT

..and this question should have been put into the sysmgmt category, sorry.
br, peterfra

Re: OpenVMS BACKUP saveset max size ?

Volker Halle — Tue, 21 Nov 2006 06:44:13 GMT

Peterfra,

welcome to the OpenVMS ITRC forum.

Backup saveset files are sequential files and are limited by the OpenVMS maximum volume size, which is currently 1 TB.

Of course you can do a BACKUP/IMAGE of a 400 GB disk. You need to provide enough disk space (or tapes) for storing the saveset.

Volker.

Re: OpenVMS BACKUP saveset max size ?

Sheldon Smith — Wed, 22 Nov 2006 14:50:55 GMT

Please correct me if I am wrong, but is not the 1 TB limit for *disk* files? So yes, an image file to a "normal" ODS disk would have a 1 TB limit. But I also seem to recall a block number in each saveset block header. Going straight to tape, with a just-under-64KB block size, how big could a tape backup be? That is, how big can the saveset block number be?

Re: OpenVMS BACKUP saveset max size ?

GuentherF — Wed, 22 Nov 2006 16:32:48 GMT

The block numbers within the save set block header are 32-bits. So that allows for save sets with enough blocks to cover more than 1 TB.

A limitation may come in from the EOF1 ANSI label. The number of blocks for a file is stored in the EOF1 label in a 6 digit ASCII string. This allows only for a maximum file of 62 GB (999999 * 63.5KB). The current BACKUP code calls $FAO to produce this string using a control string of '!6ZL'. A block count > 999999 is then returned as a string of '******' which makes it an illegal ANSI block. I haven't tested it but the BACKUP code seems to ignore this when reading the save set back. If true, your save set on tape could be larger than 62GB and even larger than 1TB.

/Guenther

Re: OpenVMS BACKUP saveset max size ?

Volker Halle — Thu, 23 Nov 2006 01:48:59 GMT

Sheldon,

based on the question 'what is the max size of a saveset file', I have answered the question under the assumption, that the destination of the saveset was a 'file on disk' and I refered the 'volume size limit'. This limitation does not apply to BACKUP savesets on tape.

For a discussion of the tape block count in EOF1/EOV1 ANSI tape labels, please refer to the following recent notes entry 1429 in the DECUServe VMS notes file:

http://eisner.decus.org/DECUServe/DECnotes/VMS/1429/SDIR.HTML

Luckily, BACKUP does not seem to care about the Block Count field in the EOF1 trailer record, but DIRECTORY/SIZE will get confused.

Volker.

Re: OpenVMS BACKUP saveset max size ?

peterfra — Fri, 24 Nov 2006 07:45:51 GMT

Thanks to everyone commenting on the issue !

So it is possible to retrieve the contents of a "large" saveset, even if the block Count field in the EOF1 field is incorrect ?

br,
peter

Re: OpenVMS BACKUP saveset max size ?

Volker Halle — Fri, 24 Nov 2006 11:52:59 GMT

Peter,

the invalid block count field in the EOF1 trailer may make the backup saveset on tape an 'invalid' ANSI file on tape, but for the purpose of BACKUP restoring that saveset, this field is not being looked at.

Volker.

Re: OpenVMS BACKUP saveset max size ?

peterfra — Thu, 30 Nov 2006 01:47:20 GMT

vms backup restores from >100GB saveset files are possible.