Level 9 dump size calculation?
jesse at wingnet.net
Fri Jan 16 09:50:20 PST 2004
I've got a machine (4.6.1-RELEASE-p10) doing
level 9 dumps over SSH to a tape drive on a remote
machine over a T1.
The machine being backed up looks like this:
# df -h
Filesystem Size Used Avail Capacity Mounted on
/dev/aacd0s1a 300M 52M 225M 19% /
/dev/aacd0s1h 2.5G 11M 2.3G 0% /tmp
/dev/aacd0s1e 12G 5.3G 5.4G 49% /usr
/dev/aacd0s1f 5.8G 1.1G 4.2G 21% /usr/home
/dev/aacd0s1g 12G 1.1G 9.6G 10% /var
procfs 4.0K 4.0K 0B 100% /proc
And my dump command looks like this:
ssh "$serverName" -nTc blowfish "/sbin/dump -0us 1000000 -f - /dev/aacd0s1a | gzip -c -3" | gunzip -cd -3 > "$tapeDriveDevice"
(machine with tape drive connects to machine to be
backed up via SSH, starts the dump on the remote
machine [with dump output piping through gzip and then
to stdout], decompresses output after it has traveled
over the T1 and finally writes it to the tape drive
I execute one dump command for /,/usr,/usr/home, and
And I get emailed output that looks like this:
DUMP: Date of this level 0 dump: Tue Jan 13 06:00:01 2004
DUMP: Date of last level 0 dump: the epoch
DUMP: Dumping /dev/aacd0s1a (/) to standard output
DUMP: mapping (Pass I) [regular files]
DUMP: mapping (Pass II) [directories]
DUMP: estimated 54069 tape blocks.
DUMP: dumping (Pass III) [directories]
DUMP: dumping (Pass IV) [regular files]
DUMP: DUMP: 54091 tape blocks
DUMP: finished in 130 seconds, throughput 416 KBytes/sec
DUMP: level 0 dump on Tue Jan 13 06:00:01 2004
DUMP: DUMP IS DONE
Granted, the above commands and output are from a level
0 dump, but my level 9s are performed in exactly the same
Here's my question:
How do I determine how large the dump output is?
The dump man page states that dump uses a blocksize of
10k by default.
54091 tape block * 10k/block = 540910k
540910k/1024 = 528.23M
Surely dump isn't expanding my 52M in / to 528.23M!!
54091k/1024 = 52.82M (which is very close to how much used
space I actually have in /)
Is dump incorrectly labeling 54091 as the number of tape
blocks when it should instead be labeling 54091 as the
number of kilobytes?
Jesse Guardiani, Systems Administrator
WingNET Internet Services,
P.O. Box 2605 // Cleveland, TN 37320-2605
423-559-LINK (v) 423-559-5145 (f)
More information about the freebsd-questions