| Title: | VAX and Alpha VMS |
| Notice: | This is a new VMSnotes, please read note 2.1 |
| Moderator: | VAXAXP::BERNARDO |
| Created: | Wed Jan 22 1997 |
| Last Modified: | Fri Jun 06 1997 |
| Last Successful Update: | Fri Jun 06 1997 |
| Number of topics: | 703 |
| Total number of notes: | 3722 |
I have a question about the amount of data, which I have on a tape.
When I mount a tape foreign, on which I have a saveset of an image
backup and do a
dir $2$mua4: /size
dcl tells me that 21565 blocks are on tape.
But I cannot count back to the disksize.
In the backup command I enter /block=64000.
How can I see, what's the blocksize/recordsize on tape, for to see how
many MB are really on tape?
A dump mua4 tells
HDR2F6400064000
kind regards
Volker
| T.R | Title | User | Personal Name | Date | Lines |
|---|---|---|---|---|---|
| 158.1 | Most Tools Show 512-byte Blocks... | XDELTA::HOFFMAN | Steve, OpenVMS Engineering | Fri Feb 07 1997 13:06 | 22 |
The BACKUP saveset/SAVE/LIST command will show the tape block size,
as well as the number of 512-byte blocks required by the files.
The DIRECTORY command shows the file sizes in 512-byte blocks.
The default settings for BACKUP create a saveset that includes some
amount of redundant information for detection and correction of tape
errors -- the size of the saveset will be larger than the total size
of the files on the tape. See the CRC and GROUP settings.
If you are comparing the size of the BACKUP to the size of the disk,
be aware that various DIRECTORY commands imply there is more data on
the disk than there actually is. This is due to directory (and file)
aliases that are present on various disks -- particularly on system
disks.
Also be aware that BACKUP/NOALIAS can greatly reduce the amount of
information written to the tape, by avoiding writing out the alias
entries. This has implications for file restorations of individual
files, as only the primary file entry can be selected for restoration.
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| 158.2 | AUSS::GARSON | DECcharity Program Office | Sun Feb 09 1997 17:12 | 11 | |
re .0
Can you explain what problem you are actually trying to solve?
Using the HDR2 label is probably reasonable. You are lucky that BACKUP
only creates fixed length records.
Note that even without redundancy group information, a saveset will be
larger than the distinct input files combined due to additional
information put in the saveset by BACKUP. (I don't believe that /[NO]CRC
has any effect on the output saveset size.)
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