Hi, I'm trying to figure out how much bytes were written to a tape by dump(8). I'm using a blocksize of 64kB to maximize throughput to the tape drive. Initially, I thought I could just add up the number of "tape blocks" written by dump and multiply by 64kB. But it looks like dump is still reporting those values as 1kB blocks. Here's some sample output: DUMP: Date of this level 1 dump: Wed Nov 15 09:46:37 2006 DUMP: Date of last level 0 dump: the epoch DUMP: Cache 256 MB, blocksize = 65536 DUMP: DUMP: 30676 tape blocks on 1 volume DUMP: finished in 1 seconds, throughput 30676 KBytes/sec DUMP: Date of this level 1 dump: Wed Nov 15 10:25:38 2006 DUMP: Date of last level 0 dump: the epoch DUMP: DUMP: 4650864 tape blocks on 1 volume DUMP: finished in 132 seconds, throughput 35233 KBytes/sec DUMP: Date of this level 1 dump: Wed Nov 15 10:50:36 2006 DUMP: Date of last level 0 dump: the epoch DUMP: DUMP: 328548 tape blocks on 1 volume DUMP: finished in 14 seconds, throughput 23467 KBytes/sec DUMP: Date of this level 1 dump: Wed Nov 15 11:00:14 2006 DUMP: Date of last level 0 dump: the epoch DUMP: DUMP: 36925423 tape blocks on 1 volume DUMP: finished in 973 seconds, throughput 37950 KBytes/sec If I add the time*throughput, I get 41GB. If I add the number of tape blocks and assume a block size of 1kB, I get 41GB, too. So, how exactly is the '-b64' parameter to dump(8) affecting the block size on tape? Uli
Ulrich Spoerlein wrote:
> I'm trying to figure out how much bytes were written to a tape by
> dump(8). I'm using a blocksize of 64kB to maximize throughput to the
> tape drive. Initially, I thought I could just add up the number of
> "tape blocks" written by dump and multiply by 64kB. But it looks
like
> dump is still reporting those values as 1kB blocks.
> [...]
> So, how exactly is the '-b64' parameter to dump(8) affecting the
block
> size on tape?
The -b option does _not_ change the blocksize of dump,
which is hardcoded at 1024 bytes and cannot be changed.
That means that the reported number of blocks is also
always measured in units of 1024 bytes, no matter what
your -b option says. Unfortunately the manual page is
somewhat misleading. :-(
Instead, the -b option changes the number of blocks per
record, i.e. how many blocks are written at once per
write operation. The default is 10 for standard tapes
and 32 for high-density tapes (>= 6250 bpi).
Best regards
Oliver
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