*BSD News Article 22511


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From: deraadt@fsa.ca (Theo de Raadt)
Subject: Re: FYI.. benchmarks on linux and 386bsd
In-Reply-To: hsu@cs.hut.fi's message of 15 Oct 1993 18: 08:53 GMT
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	<MYCROFT.93Oct6054959@duality.gnu.ai.mit.edu>
	<29klpf$8ae@kralizec.zeta.org.au>
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Date: Fri, 15 Oct 1993 19:41:06 GMT
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hsu@cs.hut.fi (Heikki Suonsivu) writes:
> bde@kralizec.zeta.org.au (Bruce Evans) writes:
> >for this and therefore risks serious file system corruption should the
> >...
> >A measly 10 to 20 times faster.  This is one thing makes Linux "feel"

> Personally, I would prefer that there would be per-filesystem option to set
> whether you wish file system structure updates done synchronously.
> Normally one wants the system be reasonably stable, but when doing large
> copies of directory trees (like moving contents of one filesystem to
> another) it would be nice to avoid extra cost of doing synchronous IO. 

No thanks. I want reliability of my filesystems during a crash.

fsck and the filesystem are supposed to work together; the filesystem
must gaurantee that writes (especially during directory operations)
are done in a repeatable order so that fsck can figure out where in
the sequence of writes the crash occurred. fsck's purpose is simple:
it is supposed to back out of those unfinished operations.

Since BSD FFS gaurantees a cluster of related writes to be done in such
an atomic way; it is much more likely that fsck can reconstruct the
filesystem. There are gauranteed to be only a few changes in-progress.
With Linux things are different: if you have a Linux machine try this:
	run both a file creation and deletion program at the same time, ie.
	% rm largedir & tar xf file.tar &
	when the disks are going, hit reset
Invariably, Linux will have more filesystem corruption than BSD.

An additional comment; I believe the BSD buffer cache clusters a few types
of operations that need not be clustered, I am hoping that Torek will jump
in here and give more details..
--
This space not left unintentionally unblank.		deraadt@fsa.ca