[TUHS] Abstractions

[Nelson H. F. Beebe]

Greg Woods responds to my posting:

>> Hmmmm... you may just be mixing up the names of the archive tools you
>> mean, but on the other hand maybe you don't know that "dump" does whole
>> filesystems, not just sub-directories.

I meant "dump" as a generic verb, not specifically the Unix dump
utility.  Many sites also used tar to backup directory trees: after
all, tar means Tape ARchiver.

>> Original Unix dump(1m) had no trouble asking for additional tapes ...

That was, however, contingent on a reliable signal from the tape unit,
and my strong recollection is that when we moved to various types of
cheap cassette tapes, the end-of-tape indicator was unreliable.  Thus,
we paid attention to both disk and tape sizes.

Today, with 10TB+ on LTO-8 tapes, it isn't an issue for us, and we
also tend to have many different ZFS volumes representing various
parts of the filesystem, allowing different backup and snapshotting
policies.  Besides tapes and snapshots, we also have a live SAN
mirror, and a remote snapshot server, giving plenty of data
replication, and the warm fuzzy feelings from that.  After 20 years of
ZFS, I don't recall us ever losing data.  We have also gone through
two generations of major fileserver upgrades and complete data
migrations without service interruptions (except for a brief interval
for each user account to synchronize data on old and new servers).

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