From: CRDGW2::CRDGW2::MRGATE::"SMTP::CRVAX.SRI.COM::RELAY-INFO-VAX" 30-OCT-1989 15:47 To: MRGATE::"ARISIA::EVERHART" Subj: Re: indexf.sys file extensions Received: From FCCC.EDU by CRVAX.SRI.COM with TCP; Mon, 30 OCT 89 07:53:22 PDT Message-Id: <2F73E126E25F80171A@fccc.edu> Date: Mon, 30 Oct 89 10:51 EST From: Frank Manion Subject: Re: indexf.sys file extensions To: INFO-VAX@SRI.COM X-Organization: The Fox Chase Cancer Center X-Vms-To: IN-INFO-VAX X-Vms-Cc: MANION In a recent reply, Jim Kirk writes: >Carl J Lydick recently wrote about >the INDEXF.SYS extension problem -- > > >It strikes me that this is a non-problem. > >Perhaps I misunderstand Carl, but the root of the problem deals with >cluster nodes simultaneously attempting to extend the file. Jim is certainly right in that this is a valid reason (preventing the extension of the index file, and hence the infamous V5.x file sytem bug), however, there is another case to watch out for with regard to index file extension. Dec, in their wisdom, has HARDCODED a value of 1000 blocks into the size for the INDEXF.SYS header extension quantity (the actual value used may be slightly larger, based on your disks cluster factor). Since a retrieval pointer of the range 256-1024 blocks uses an 8 byte retreival pointer, and since a file header has room for about 50 8 byte retreival pointers, and since the index file can't have extension headers, IF YOU DON'T PREALLOCATE A REASONABLE NUMBER OF HEADERS FOR YOUR ENVIRONMENT, YOU CAN GET BURNED WHEN THE INDEX FILE HEADER for INDEXF.SYS BECOMES FULL OF 1000 BLOCK POINTERS. This is true even if you INIT'd/MAXFILES=n (where N is some number greater than 50000). The above "feature" got us on some 3rd party 2.4G disk drives. Most sites that run BACKUP save/restore cycles won't see this, as the allocated index file space is made contiguous (and hence only uses one retreival pointer). We choose not to do that because of the time required to backup all our 2.4G disks. Instead we run a well known disk defragmentation utility and back the disks up online during quite periods. Note that the above "gotcha" can bite you even if you only have a RA81, but, of course is more likely the larger your disks get. We currently have about 70,000 files on our most used disk. Carl Lydick is correct in his analysis of working around this problem, but only if it is done BEFORE you get into trouble with a full index file file header. -- Frank :-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-: Reply to: MANION@FCCC.EDU Frank J. Manion or: Mgr. of Systems and Applications MANION@CURIE.RM.FCCC.EDU The Fox Chase Cancer Center 7701 Burholme Avenue Phone: (215) 728-3660 Philadelphia, PA 19111 USA :-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-: