Dr. Blinn had these clarifications/corrections.
Thanks Tom!!
> > Suggestion 1:
> > Compaq support suggested that my ufs hit rate was too low and that is
> should
> > increase the size of the ubc (to
> > ubc-maxpercent=50,vm-ubcseqstartpercent=50). Apparently Advfs volumes
> (our
> > Oracle database) uses the ubc, while Ufs volumes do not.
> >
> > You can calculate your ufs hit rate:
> > # echo "pd vm_perfsum" | dbx -k /vmunix |grep lookup
>
> You are confusing "UFS" and "UBC". You may also be confusing AdvFS or
> UFS file systems with Oracle raw disk accesses.
>
> "UBC" is the "unified buffer cache". It was INVENTED precisely to work
> with the Berkeley UNIX fast file system, which is the basis for the "UFS"
> file system in Tru64 UNIX. The "AdvFS" file system was originally not a
> UNIX file system at all (it was invented for an operating system project
> that never reached product status, and the original design lives on both
> in the Tru64 UNIX AdvFS file system and in Microsoft's NTFS, but don't
> get me started...). Originally (before V5.x), AdvFS did not work great
> with the UBC, it had its own private data and metadata caches, and to the
> extent that it worked with the UBC, it did it through back doors. Now,
> it works MUCH better in V5.x with lots of performance improvements. Our
> AdvFS team put a LOT of effort into the V5.x releases and it shows in a
> better product.
>
> Oracle provides the option of layering on a native file system (such as
> AdvFS) or using raw disk volumes. Raw disk I/O is NEVER cached through
> the UBC, just as tape I/O (raw device access) is not. Only I/O through
> a native UNIX file system (now including AdvFS) is cached in the UBC.
>
> It's really easy to get this stuff confused, and I'm sure that there are
> many folks who don't have all the details down pat. Too many three letter
> abbreviations that are much alike, like a maze of twisty passages..
>
> ------- End of Forwarded Message
>
> Tom
>
> Dr. Thomas P. Blinn + UNIX Software Group + Compaq Computer Corporation
> 110 Spit Brook Road, MS ZKO3-2/W17 Nashua, New Hampshire 03062-2698
> Technology Partnership Engineering Phone: (603) 884-0646
> Internet: tpb_at_zk3.dec.com - or - thomas.blinn_at_compaq.com
> ACM Member: tpblinn_at_acm.org PC_at_Home: tom_at_felines.mv.net
>
> Worry kills more people than work because more people worry than work.
>
> Keep your stick on the ice. -- Steve Smith ("Red Green")
>
> My favorite palindrome is: Satan, oscillate my metallic sonatas.
> -- Phil Agre, pagre_at_alpha.oac.ucla.edu
>
> Yesterday it worked / Today it is not working / UNIX is like that
> -- apologies to Margaret Segall
>
> Opinions expressed herein are my own, and do not necessarily represent
> those of my employer or anyone else, living or dead, real or imagined.
>
Received on Thu Mar 14 2002 - 20:34:36 NZDT