cire@dustbin.cisco.com (Eric B. Decker) (08/17/89)
I am dealing with a hard disk problem that is formated using the Fast File System. I know almost nothing about FFS and have no documentation for it. I have lots of other documentation but not that stuff. One of the things I was wondering is how does it ensure data integrity. So my two questions are 1) How does the FFS deal with data integrity? Is there some kind of checksum or other protection mechanism? 2) Where can I find detailed specifications of the FFS? Thanks, -c -- cire|eric Eric B. Decker Token Ring Development cisco Systems - engineering Menlo Park, California email: cire@cisco.com uSnail: 1360 Willow Rd., Menlo Park, CA 94025 Phone : (415) 326-1941
lphillips@lpami.wimsey.bc.ca (Larry Phillips) (08/18/89)
In <CIRE.89Aug16133920@dustbin.cisco.com>, cire@dustbin.cisco.com (Eric B. Decker) writes: >2) Where can I find detailed specifications of the FFS? I don't know of anywhere you can find the details offhand, but here are all the differences I know of between the old and new file system. -------------------- Block 0 (Cyl 0, Head 0, Sector 0 on any partition), contains: OFS: 'DOS',0 FFS: 'DOS',1 -------------------- Root block: FFS can have an extension to the bitmap pointer table. The pointer to the next sector containing pointers to bitmap pages is contained in longword $68 -------------------- Hash chain extensions are sorted in increasing order of blocks pointed to. -------------------- File data blocks contain 512 bytes of data, with none of the overhead contained in the OFS scheme. This results in a tradeoff. You trade considerable speed for less recoverability. -------------------- -larry -- "So what the hell are we going to do with a Sun?" - Darlene Phillips - +-----------------------------------------------------------------------+ | // Larry Phillips | | \X/ lphillips@lpami.wimsey.bc.ca -or- uunet!van-bc!lpami!lphillips | | COMPUSERVE: 76703,4322 -or- 76703.4322@compuserve.com | +-----------------------------------------------------------------------+