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Slow listing of LTo5 tape contents


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Old Unix and Linux 05-07-2013
m_raheelahmed m_raheelahmed is offline
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IBM Slow listing of LTo5 tape contents


We are taking our filesystem backup having size of 1.3 TB on LTO5 catridges using the following command

find * -print|backup -ivf '/dev/rmt0' '-U'

i.e backup byname and it took about 6.5 Hours to complete When we are listing same tape contents using the following command

restore -lTf '/dev/rmt0'

then it took almost the same time to list the contents in which backup was completed. Is there any way to fasten the tape content listing? Any help any idea would be highly appreciated.
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Old Unix and Linux 05-12-2013
bakunin bakunin is offline Forum Staff  
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The problem is that "restore"/"backup" file format has no "table of contents", so basically "restore" has to read the whole file to generate it. The limiting factor is the speed of the tape (this is probably the case with the "backup" too).

What you can do is: instead of piping the file list directly into "backup" create a file first. Then write this file first at the rmt-device, only then use the same list as input to "backup". Write to the "/dev/rmtN.1" instead of "/dev/rmtN", this is the drive without "rewind on exit", so your "table of contents" will be the first entry on the cartridge. You can restore this single file to get/search a list of files backed up in this session.

Backup (schematic)

find .... -print > /tmp/filestobackup
tctl -f /dev/rmtN.1 rewind
tar cf /dev/rmtN.1 /tmp/filestobackup
backup -ivf /dev/rmtN.1 < /tmp/filestobackup
tctl -f /dev/rmtN rewoffl

Search (=restore toc only)

tar xf /dev/rmtN

Restore (schematic, skip first entry, then restore normally)

tctl fsf 1 -f /dev/rmtN.1
restore -lTf /dev/rmtN.1

I hope this helps.

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