This may be an old topic or the wrong forum. If so, please point me in the right direction.
I've had a sporadic issue with ITDT on a fairly large Linux system for a while. I supose "large" is realative, but for context we have 27 tape drives and a total of 1745 SG devices on a Linux x64 system, which is a MDS for Versity VSM (clone of SAM/QFS, which is probably more familiar). At any rate, the issue is that occaisionally ITDT does not recognized all the tape drives on the system, although the system itself and userland tools such as mt and mtx, as well as VSM itself, do. I've looked high and low and found a few complaints on this issue, but no solution (other than be sure ITDT is up to date, check interfaces, etc.). In re-reading the user manual (ya, maybe I should have started here), I noticed that AIX has a known issue with FC or SAS ID or LUN > 999 and that got me thinking about the number of SG devices we have attached. My original thought was that it might be a 3 digit device number limit. But when I did a strace of './itdt scan', I found that ITDT attempts to open all available SG devices up to 2048 before reading info from them. That was a bit surprising, but the issue became obvious when I saw that all device opens at 1021 and following failed, namely that filehandles per pid was exhausted (default is 1024, minus 1 each for STDIN, STDOUT, and STDERR). E.g. pertinent clip:
# egrep 'open\("/dev/sg.*' /vsmadmin/tmp/itdt_scan.strace | grep -B2 EMFILE | head -3
262100 open("/dev/sg1019", O_RDWR|O_NONBLOCK) = 1022
262100 open("/dev/sg1020", O_RDWR|O_NONBLOCK) = 1023
262100 open("/dev/sg1021", O_RDWR|O_NONBLOCK) = -1 EMFILE (Too many open files)
Simple solution, 'ulimit -n 2051' (or some number >= max SG devs + 3) before running itdt.
I found this forum after I found the answer, but thought I'd post it anyway, in case someone is suffering the same issue. It might even be worthy of a known issue note in the user guide, but I can't find where to post suggestions for that either. I advocate RTFM and that "man is your friend", but seems to be a gap on this one.
Hope this helps someone else in the universe.
------------------------------
Greg Land
------------------------------