Does anyone know a means whereby a user can force a flush of the
UBC to disk?
We have noted that on a lightly loaded machine, if a user does a copy
of a large amount of data from one disk to another, the data
may not actually reach the destination disk for some time, but sits in the
UBC instead. If the user then does a diff on these files to make
sure that the copy is OK, a) he is not checking the source against
disk copy, but merely a copy possibly all in UBC, and b) if
he then deletes the source and the machine crashes before the
UBC is flushed, large amounts of data can be lost.
With a ubc_maxpercent = 100 and 4Gb mem, I have seen it take
5 minutes to umount a disk (the only way I know to force such a flush)
after a filesystem copy to it. sync doesnt achieve this, despite the
statement in the man pages that sync writes all unwritten system-buffers
to disk. Does anyone have a feeling for the likely performance-hit
if I mount all disks -osync?
Cheers,
Terry.
Terry Horsnell (tsh_at_mrc-lmb.cam.ac.uk)
Computer Manager
Medical Research Council
Lab of Molecular Biology
Hills Road
CAMBRIDGE CB2 2QH
U.K.
+44 (0)1223 248011
Received on Fri Oct 08 1999 - 12:45:16 NZDT