mp@allegra.tempo.nj.att.com (Mark Plotnick) (07/24/90)
A number of people here run a program that creates and deletes dozens of
50- to 200-MByte files during its 14-hour run. They run it on several
4/390's, each with 4 to 8 1GB IPI disks. Each filesystem is a full disk
in size, but even these 1GB filesystems are inconveniently small; the
users either have to free up space on a filesystem before starting the
program, or have to use symbolic links to spread out the program's files
over several filesystems.
I'd like to know of any products that let filesystems span more than one
physical drive. From the paragraph describing SPARCserver manager in the
May 15th press release, it seems it might do this, ("SPARCserver Manager
also allows files to span disks") but my sales rep has been unable to
provide any additional information.
What we'd like to do is have 3 to 6 disks treated as one filesystem.
Ideally, the failure of one disk would not necessitate restoring the
others from tape, but we can live with that (time to get that Exabyte
jukebox, I suppose). We'd also prefer that the inodes are kept
appropriately numbered so that the method that tar and cpio use to check
for hard links doesn't result in files being omitted from tape dumps.
Mark Plotnick
mp@allegra.att.comjms@tardis.tymnet.com (Joe Smith) (08/04/90)
In article <10174@brazos.Rice.edu> mp@allegra.tempo.nj.att.com (Mark Plotnick) writes: >Each filesystem is a full disk in size, but even these 1GB filesystems are >inconveniently small. I'd like to know of any products that let filesystems >span more than one physical drive. What we'd like to do is have 3 to 6 >disks treated as one filesystem. Ideally, the failure of one disk would not >necessitate restoring the others from tape. I don't know of a software solution, but Interphase Corporation displayed a hardware solution at the Sun Expo '90 in San Jose. They can provide a box that sits at the end of a SCSI bus that uses several disks to create the illusion of one giant disk. They have an article in "The Sun Observer", page 60 of the July 1990 issue. It mentions how "spanning" allows a single partition to be larger than a full disk. They also had a session describing the advantages of "striping", where the host's I/O request is split into several parts, each going to a different drive. For instance, a SunOS request for 8K bytes could be split into 4 requests of two 1K byte blocks each, and read/written from/to 4 drives in parallel. Sustained thruput is 4 times that of a single disk. Another way to go is to separate the individual bits. Interphase described one product has five 1GB disks but acts like a single 4GB disk. Incoming data is split, with 1/4th of the bits going to drive 1, 1/4th to drive 2, 1/4th to drive 3, and the rest to drive 4. Drive 5 provides parity for the other 4 bits. There is enough redundancy that it can survive the complete failure of a single disk. As long as a replacement disk can be hooked up and made up-to-date before a second disk fails, then no data will be lost. I'm sure other companies are working on similar products. Interphase Corporation is at 13800 Senlac, Dallas, TX 75234 (214)919-9000. I am not a customer, I just listened to them at Sun Expo. Joe Smith (408)922-6220 | SMTP: jms@tardis.tymnet.com or jms@gemini.tymnet.com BT Tymnet Tech Services | UUCP: ...!{ames,pyramid}!oliveb!tymix!tardis!jms PO Box 49019, MS-C41 | BIX: smithjoe | 12 PDP-10s still running! "POPJ P," San Jose, CA 95161-9019 | humorous dislaimer: "My Amiga speaks for me."