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From: Terry Lambert <terry@lambert.org>
Newsgroups: comp.unix.bsd.freebsd.misc,comp.os.linux.development.system
Subject: Re: The better (more suitable)Unix?? FreeBSD or Linux
Date: 17 Feb 1996 22:19:17 GMT
Organization: Utah Valley State College, Orem, Utah
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Message-ID: <4g5k95$28m@park.uvsc.edu>
References: <4er9hp$5ng@orb.direct.ca> <31220995.C4C54C1@acm.org> <4g0sam$r6p@agate.berkeley.edu> <4g33tp$esr@park.uvsc.edu> <4g57cj$gc3@pell.pell.chi.il.us>
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Xref: euryale.cc.adfa.oz.au comp.unix.bsd.freebsd.misc:14582 comp.os.linux.development.system:18298
orc@pell.chi.il.us (Orc) wrote:
[ ... the Lai/Baker paper ... ]
] But alternatively, one might wonder what's the point of writing
] the metadata unless you're also writing the data that the metadata
] is pointing to. If the synchonous metadata writes that some
] filesystem provide will happily put the filesystem information down
] but then defer the data writes for a later date, that information
] is completely useless and possibly harmful, and it doesn't make any
] difference whether it's written out by religious mandate or by the
] elevator passing by that floor.
That's an easy one to answer: so if you screw up, you *only*
screw up the data that you are writing instead of screwing up
all the data on the file system (or at least some of the data
that was there before and totally uninvolved in the screwed
transaction).
It's a limitation on the amount of damage you can do.
[ ... ]
] Yes, and this is a known problem with Linux. Will it stay that way?
] Dunno; certainly people are looking at the buffer caching and changes
] may happen to it. But from my experience of relative performance (Linux
] 1.2 vs FreeBSD 2.0), this behavior is hidden by the default behavior of
] the ext2 filesystem, which shows that it's hard to point at one behavior
] of a system and say whether or not it's speeding things up or slowing it
] down in regards to another system.
For me, this is not a "Linux vs. BSD" issue.
Unordered metadata writes are bogus, period. Sync writes are one
method (the only method currently implemented in either OS) to get
away from this bogosity.
Terry Lambert
terry@cs.weber.edu
---
Any opinions in this posting are my own and not those of my present
or previous employers.