Hi!
I manage AS/400 server. There exist some interestion solution of
serious problem which concerns all Unixes. Namely this is filesystem
shortage. Supose You have application which has very intensive
filesystem usage and there is end of the free space on the disk. Of
course application stops and this situation is usually serious
condition. Best practice in such situation learn to place data of such
application on separet fielsystem in order to not interfere on OS
stability. But in such situation You usualy lost some portion of data:
because of free space shortage it cannot be written.
There is simple solution of this problem on AS/400: it is named
threshold. You assign into filesystem variable named theshold, which
value is percentage of free space at which administrator of the machine
should get information about shortage. Symultaneously, all operation on
such filesystem is switched into special state in which only certain
and critical data may be written, or even disk is read only, but
application data stil may be written on system partition ( maybe better
solution is to write it on special prepeared partition dedicated for
such purposes) together with metadata which are important for safe
write of the data. At the end administrator may use it in order to
write the moust acurate data on the disk, but _after_ solving problems
with disk shortage: it may do a cleaning, remove unimportant data, or
sometimes do last backup before system crashes.
I thin it is very important mechanism, to add to filesystem. You may
use iton high availability servers specially one with large database
instances.
Thanks
Kazek Kurz
PS. I send this message to linux.kernel list but robot refuse it. I do
not know why....
Linux