Path: utzoo!utgpu!water!watmath!clyde!rutgers!mcnc!gatech!rebel!george
From: george@rebel.UUCP (George M. Sipe)
Newsgroups: comp.os.misc
Subject: Re: OS features
Message-ID: <21545@rebel.UUCP>
Date: 16 Dec 87 19:05:16 GMT
References: <561@amethyst.ma.arizona.edu> <3228@tut.cis.ohio-state.edu>
Reply-To: george@rebel.UUCP (George M. Sipe)
Distribution: na
Organization: Tolerant Systems, Atlanta GA
Lines: 38

chris@spock writes:
>	One of the features of AOS/VS (Data General) that I like is its
>   variable element size. Files are made up of elements of a given number
>   of blocks. For example, if a file's element size is 10 blocks, the file
>   will grow in chunks of 10 blocks at a time...
>   ...I haven't seen this feature
>   on any other operating system. Has anyone else?

karl@mumble.cis.ohio-state.edu (Karl Kleinpaste) writes:
>Computer Consoles, Inc's PERPOS of a couple of years back supported
>contiguous file creation.  You had to give it the total size of the
>file required, as I recall, no file growth once it's created.  PERPOS
>(a fault-tolerant UNIX derivative) was intended for a heavy
>transaction-oriented system, which made this sort of use important.

Fair warning:  Description follows of product by a company with which I
have absolutely no association other than as a full time employee :-).

Tolerant's TX (a distant 4.2 derivative) allocates files by extents
rather that blocks.  Each file may have one primary extent and as many
secondary extents as necessary.  Both extent sizes may be from 1kb to
8mb in even powers of 2.  Each file system has defaults for both
primary and secondary extents (usually 8kb).  Extent sizes are set by a
setext() system call on files of null length.  An extentsize() library
call determines optimal extent sizes (to need only 1 inode) for a file
given an expected filesize.  Cylinder boundaries are taken into account
during allocation, free space is recombined on removal.  All system
commands (e.g. tar) set extents.  Existing programs benefit from the
addition of the setext() call, but run no worse without it then they
do on most other Unix systems.

This system is fully fault tolerant, designed for high performance
communications systems and OLTP applications (transaction management
is integral).
-- 
George M. Sipe,		Phone: (404) 662-1533
Tolerant Systems, 6961 Peachtree Industrial, Norcross, GA  30071
UUCP: ...!{decvax,hplabs,ihnp4,linus,rutgers,seismo}!gatech!rebel!george