jthomas@nmsu.edu (James Thomas) (12/09/89)
This is a belated response to the previous discussion on disk partitioning. There was a question as to why anyone would want sizes other than the wonderful :-) ones picked by HP (or several other manufacturers). I've collected these. Reasons for wanting arbitrary, user-settable partition sizes: 1) Security. The easiest thing to do is to allocate the whole disk as one big partition and not worry about how much is needed for each file system. But when (not if, it will happen) the disk crashes or the file system gets corrupted, the whole partition has to be put back (taking a long time on a big disk). Of course if the disk crashed, the whole disk has to be put back sooner or later, but perhaps the smaller partitions could more easily be stashed somewhere temporarily. 2) Security, type 2. Some types of data like to be kept separate for secrecy reasons. unix(tm) does not provide all that much security, but having the file system not mounted most of the time can help. 3) Quotas. Someone mentioned that since the quota system now exists, the old use of filesystems to limit disk usage was no longer needed. But, especially in a universiy environment, there are two kinds of quotas. The quota system puts a limit on what each user can have. But it is also useful to put a limit on what a group of users can glom onto; filesystems get used for this (a very common example being /tmp). 4) Backups. Filesystems are useful for separating out to-be-backed-up files from not-to-be-backed-up files. Of course with fbackup this is no longer the reasonable way to accomplish this. 5) Load balancing. I want to put the swap area in the middle of the disk. (Unfortunately unix(tm) doesn't support that properly - oh for TOPS-10 :-) To do that, I need to define arbitrary partition sizes. (It would also be nice to have a newfs option that put the inodes at the high end or - or even anywhere in - a file system, hint, hint. Especially if I make the whole disk a single partition, being able to put the inodes smack in the middle for purposes of seek optimization. TOPS-10 strikes again :-) 6) Root. The current problem of the root filesystem being too small on 800 systems is really unacceptable. I can solve that on my system if I can adjust partition sizes. (On an 840, what happens if the root partition is put into section 15? I've RTFM'ed and don't see that defined as a legal possibility. The boot path has four extra ".0"'s - does one of them specify the unix(tm) major/minor device number as is typed later when coming up by hand? Or does the fact that section 15 starts at the right place work because ISL isn't smart enough to know any better?) Did I leave any reasons out? Jim Thomas not easily reachable at midas!jthomas@wsmr-emh82.army.mil