robert@shangri-la.gatech.edu (Robert Viduya) (09/15/90)
We got 3.3 earlier this week and I've been reading over the manuals trying to plan an install later this month. One of our systems has 4 780M disks and I was thinking of combining parts of all four into one giant logical volume and use it for user file space (one of the biggest pains in the rear on our other systems has been balancing disk utilitization across multiple file systems dedicated to users). Well, as I was working out the details, I realized that the resulting logical volume would end up being well over 2G long. Furthermore, we may be adding more disk in the future and I'd like to be able to just add them to the logical volume. What happens if it goes over 4G? With a 32-bit int/long, we can get a maximum of 2G (signed) or 4G (unsigned). The 3.3 manuals say you can keep adding disk partitions to logical partitions and doesn't mention any limits at all. Somehow I would be very surprised if this were true (pleasantly surprised, but surprised nonetheless). The man page for statfs(2) seems to indicate that it could handle a file system that was 1024G long (using 512-byte blocks), but the man page for stat(2) indicates that the max file size is 2G. If this is truely the case, I'd be satisfied; we probably aren't going to have very many files over a gigabyte. Has anyone who's gotten 3.3 played with this stuff yet? Is there a limit on how large logical volumes can be? robert -- Robert Viduya robert@shangri-la.gatech.edu Technical Services / Office of Information Technology Georgia Institute of Technology (404) 894-6296 Atlanta, Georgia 30332-0275
jwag@moose.asd.sgi.com (Chris Wagner) (09/18/90)
In article <13693@hydra.gatech.EDU>, robert@shangri-la.gatech.edu (Robert Viduya) writes: > We got 3.3 earlier this week and I've been reading over the manuals trying > to plan an install later this month. One of our systems has 4 780M disks > and I was thinking of combining parts of all four into one giant logical > volume and use it for user file space (one of the biggest pains in the > rear on our other systems has been balancing disk utilitization across > multiple file systems dedicated to users). Well, as I was working out > the details, I realized that the resulting logical volume would end up > being well over 2G long. Furthermore, we may be adding more disk in the > future and I'd like to be able to just add them to the logical volume. > What happens if it goes over 4G? With a 32-bit int/long, we can get a > maximum of 2G (signed) or 4G (unsigned). The 3.3 manuals say you can keep > adding disk partitions to logical partitions and doesn't mention any limits > at all. Somehow I would be very surprised if this were true (pleasantly > surprised, but surprised nonetheless). > > The man page for statfs(2) seems to indicate that it could handle a > file system that was 1024G long (using 512-byte blocks), but the man > page for stat(2) indicates that the max file size is 2G. If this is > truely the case, I'd be satisfied; we probably aren't going to have very > many files over a gigabyte. > > Has anyone who's gotten 3.3 played with this stuff yet? Is there a limit > on how large logical volumes can be? > > robert Well, there is some missing dicumentation! In 3.3 the maximum file size is still 2G (cause of lseek, etc). The maximum file SYSTEM size is 8G due currently to on-disk space limitations. Chris Wagner
daveh@xtenk.asd.sgi.com (David A Higgen) (09/18/90)
In article <13693@hydra.gatech.EDU>, robert@shangri-la.gatech.edu (Robert Viduya) writes: > Has anyone who's gotten 3.3 played with this stuff yet? Is there a limit > on how large logical volumes can be? Guess this is my baby, since I'm the logical volume originator. Yes, logical volumes (and filesystems thereon) may exceed 2 gig, though the size of regular files is still limited to 2 gig by the 'signed long' nature of the lseek argument. (And the fact that regular filesize is stored internally as a signed long, which precludes playing any tricks with SEEK_CUR or SEEK_END). There is actually an 8 gig limit to the size of a filesystem, imposed by some data structures in the on-disk filesystem stuff. Logical volumes themselves have no (practical) limit, but 8 gig is the maximum size of filesystem you can put on one. Oops, I don't think this is documented in the mkfs man page... mea culpa for that: however, you will get a reasonably self-explanatory error message from mkfs if you try to make a filesystem bigger than 8 gig. Or if you try to grow an existing one to over 8 gig with growfs (just a little plug here, folks: existing filesystems can be grown without losing their contents in 3.3. Check out growfs(1M)!). Two further hints: if you're concerned with balancing disk usage, it's probably worth setting your logical volume up as a striped volume; this will distribute traffic evenly amoung your disks and give you a better overall throughput in a multiuser situation. Also, with SCSI disks, you will get improved performance if you use the mount option to increase the filesystem "logical block size" to larger than its default. See the mount(1m) man page: basically you should add "lbsize=65536" to the mount options. Dave Higgen (daveh@xtenk.asd.sgi.com)