All-

Server: Red Hat Linux AS 2.1, NetWorker 7.1.3 build 421
Clients: various, for this example Red Hat Linux AS 4, NetWorker 7.1.3
build 421


On LP64 Linux clients, such as Red Hat Linux 4 on an EM64T system, certain
sparse files are enormous.  The /var/log/lastlog file on many of our
systems is 1.2 TB, though because it's sparse it's actually only using 92
KB of disk space.

Even though "save" and other NetWorker commands handle sparse files
correctly, there's still a bit of an issue when dealing with a file like
this.  When save backs it up, it opens it and happily starts reading the
file in 64K chunks.  Even assuming save can read 256 MB a second this
way (which it probably can't, because of the read size), if you do the
math you'll see that it takes

    1.2 TB == 1258291 MB

    1258291 MB
    ----------  = 4915 seconds
     256 MB/s


Or, about an hour and 20 minutes of reading 64K chunks of nulls, all to
back up a file that has 92 KB of real data in it.

How are others dealing with this?  Are you skipping files like this using
"skip" or "null" directives?  Is there a way to increase the buffer size
that "save" uses for reads?

Tim
--
Tim Mooney                              mooney AT dogbert.cc.ndsu.NoDak DOT edu
Information Technology Services         (701) 231-1076 (Voice)
Room 242-J6, IACC Building              (701) 231-8541 (Fax)
North Dakota State University, Fargo, ND 58105-5164

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