steveb@aostul.UUCP (Steve Bogner) (07/15/89)
We have a large (potential) customer that wants an SCO Unix system that is "fault tolerant" (in the Novell LAN sense). This would include "disk mirroring" or "disk duplexing" where a second hard disk is maintained as an exact image of the primary disk. The reasoning goes that if the primary disk goes bad, they can automatically run off the second disk without any difficulty. Does anyone know if there is such an animal? ------------------------------------------------------------------------- Steve Bogner UUCP: !uunet!sco!aostul!steveb AOS Network Solutions 2424 E. 21st St. Ste. 100 Tulsa, Oklahoma 74114 PH 918-742-6400
karl@ddsw1.MCS.COM (Karl Denninger) (07/17/89)
In article <14@aostul.UUCP> steveb@aostul.UUCP (Steve Bogner) writes: > >We have a large (potential) customer that wants an SCO Unix system >that is "fault tolerant" (in the Novell LAN sense). This would >include "disk mirroring" or "disk duplexing" where a second hard disk >is maintained as an exact image of the primary disk. The reasoning >goes that if the primary disk goes bad, they can automatically run off >the second disk without any difficulty. Does anyone know if there is >such an animal? Get the DPT disk controller and forget about it. They can do on-board shadowing, removing the operating system from the loop entirely -- and they cache disk accesses as well! Nice board, even if a little expensive. (but for unbelievably fast performance, I'll pay their price) -- Karl Denninger (karl@ddsw1.MCS.COM, <well-connected>!ddsw1!karl) Public Access Data Line: [+1 312 566-8911], Voice: [+1 312 566-8910] Macro Computer Solutions, Inc. "Quality Solutions at a Fair Price"
clewis@eci386.uucp (Chris Lewis) (07/20/89)
In article <14@aostul.UUCP> steveb@aostul.UUCP (Steve Bogner) writes: > >We have a large (potential) customer that wants an SCO Unix system >that is "fault tolerant" (in the Novell LAN sense). This would >include "disk mirroring" or "disk duplexing" where a second hard disk >is maintained as an exact image of the primary disk. The reasoning >goes that if the primary disk goes bad, they can automatically run off >the second disk without any difficulty. Does anyone know if there is >such an animal? This *might* be moderately easy to do if you don't get too petrified by playing with drivers. The disk drivers have open, close, read, write entries. Create a new pseudo driver that: - has the same entries as the disk driver. - each open/read/write entry examines its minor number, and for each minor number you want to mirror (you *probably* want to mirror the *whole* disk), call the regular disk driver, and then call it again with the minor number of the same partition of the second disk. (Usually by simply or'ing in a bit into the minor). Obviously you *don't* want to do this with "reads" ;-). - set this new driver as the driver that the O/S uses for the disks in question - eg: you may want to change the root device, /dev/usr major/minor numbers etc. Then, you have to build the two disks to be EXACT duplicates of the other (except of course for bad blocks). This could be done by building a kernel with write mirroring, putting it on a boot floppy, booting with it, and doing the rest of the installation that way. It's tricky tho - fsck would be reading from one disk to find defects and would be correcting all defects on *both* drives - which may not be the same. A better approach would be to confirm that the disk is okay and fsck it thru the *original* (non-duplicating) driver entries, and then copy the whole drive to the other disk. I'm not sure from an operational standpoint whether this could be made feasible and/or bullet-proof enough to do this to the root disk. Then again, you could do it on specific partitions without too much difficulty. *Don't* do it to the swap device. Prepare to be hit with a performance penalty too (even if you do get fancy and manage to get the pseudo driver to call both drivers simultaneously). And, you would have to play around with creating additional disk buffers (the two invocations would have to have different buffers for the write buffers). Better yet, sell 'em a NCR Tower with SCSI disks and turn mirroring on there.... -- Chris Lewis, R.H. Lathwell & Associates: Elegant Communications Inc. UUCP: {uunet!mnetor, utcsri!utzoo}!lsuc!eci386!clewis Phone: (416)-595-5425
jon_hogan-doran%713.602@fidogate.fido.oz (Jon Hogan-doran) (08/02/89)
Original to: clewis@eci386_uucp
> re: Disk Mirroring
I believe that in either June or July UNIXworld (c) there is an
advertisement for a disk mirroring system which runs under SCO XENIX.
Unfortunately I can't find the magazine at the moment. It was in the
first 15 pages, spread over two pages with a background of
two "twin" babies.
--- Zeta
* Origin: Zeta: Unix, Minix, Xenix support (02) 627-4177 (3:713/602)jbayer@ispi.UUCP (Jonathan Bayer) (08/04/89)
jon_hogan-doran%713.602@fidogate.fido.oz (Jon Hogan-doran) writes: >Original to: clewis@eci386_uucp >> re: Disk Mirroring > >I believe that in either June or July UNIXworld (c) there is an >advertisement for a disk mirroring system which runs under SCO XENIX. >Unfortunately I can't find the magazine at the moment. It was in the >first 15 pages, spread over two pages with a background of >two "twin" babies. The company's name is 1776, Inc. I got their brochure a while ago. Looks pretty good although expensive. JB -- Jonathan Bayer Beware: The light at the end of the Intelligent Software Products, Inc. tunnel may be an oncoming dragon 500 Oakwood Ave. ...uunet!ispi!root Roselle Park, NJ 07204 (201) 245-5922 jbayer@ispi.UUCP