In an effort to get "point-in-time-restore" capability for a few of our crutial
systems, I've been looking at EXPORT NODE. The process is not a
pretty sight. :-(
EXPORT NODE is good because it doesn't cost me DB
space. It is bad because I have to manage the process
including what's where. But the reason for this mail are
a few other problems ...
A minor problem: the EXPORT NODE messages are not returned to the
command sender, at least when entered via the SMSG interface (they are
in the ACTLOG and are nicely labeled EXPORT NODE).
A less minor problem: the number of bytes to be copied was reported as
a negative number for my 2-3 gigabyte node. (There is an open (last I
looked) problem on this). The actual amount of data copied is also a
negative number; I'm not sure if this is the same message or another
problem.
A strange-ness, but not necessarily a problem: if you don't give ADSM
enough volsers on which to place the data, ADSM issues a mount for
volume "export.n", where "n" is one more than the number of volsers you
gave it. Not a problem, but not documented (anyplace I could find).
A larger problem was the cpu and wall-clock time used. An EXPORT
NODE with PREVIEW=YES crunched for a couple of hours on a smallish
50,000 file node. I canceled a similar request on a 250,000+ file node a
day or so later. In all cases, a QUERY PROCESS output seems to imply
ADSM is sorting. Actually writing to tape was no better. On a recent trial,
ADSM took the following times filling 3490 cartridges: 80 minutes, 25
minutes, 190 minutes, and 60 minutes (with no interference from other
applications). Given that our mainframe backup software (SYBACK) can
spinoff a tape in 10 minutes or less ... this is horrible. Considering what
the PREVIEW=YES took, it's not unexpected.
These things just make EXPORT NODE less useful. Where I have my
ADSM server physically close to client nodes, it makes "offsite backup"
expensive indeed.
Thanks for listening,
cheers,
Wayne T. Smith
Systems Group -- CAPS internet: wts AT maine.maine DOT edu
University of Maine System BITNET/CREN: WTS@MAINE
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