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ufs logging

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Dominick DiMantova

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Jan 27, 2003, 1:27:13 PM1/27/03
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Hello, all of you gurus,

Can someone tell me what exactly is the purpose of ufs logging? I have
somewhat of an idea: You want to log transactions/changes into a log
file. But, at the O/S level, what kinds of tranactions are we talking
about? I know that, in an Oracle database, you have redo log files,
which stores changes that was made, at a point in time, in a database,
which are transactions, I believe. Now, is this a similiar concept of
ufs logging? I'd appreciate some intelligent feedback. Thank you.

Casper Berris

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Jan 27, 2003, 1:39:42 PM1/27/03
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For more info about UFS logging:
http://docs.sun.com/db/doc/806-6111/6jf2ve3ha?a=view


"Dominick DiMantova" <domi...@cyberspace.org> wrote in message
news:f222f979.0301...@posting.google.com...

Rich Teer

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Jan 27, 2003, 2:12:04 PM1/27/03
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On 27 Jan 2003, Dominick DiMantova wrote:

> Can someone tell me what exactly is the purpose of ufs logging? I have

It's to reduce (or eliminate entirely) the time required for
an fsck should a file system go down unexpectedly (e.g.,
a power cut).

> somewhat of an idea: You want to log transactions/changes into a log
> file. But, at the O/S level, what kinds of tranactions are we talking

Changes to files and their permissions. E.g., chmod and chown.

--
Rich Teer

President,
Rite Online Inc.

Voice: +1 (250) 979-1638
URL: http://www.rite-online.net

Darren Dunham

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Jan 29, 2003, 2:54:28 AM1/29/03
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A filesystem is really quite similar to a database in several ways.

Like a database, it has sections of data that are related to each other,
and must be updated "atomically" to maintain consistency.

This usually occurs with the creation or removal of files. When you
create a file, the OS must..

Take a free inode and allocate it.
Populate the inode and point to the data block(s).
Create an entry in a directory, and point to the inode.

So, this could be considered a filesystem transaction. The UFS logging
support can replay the entire sequence if needed after a crash.

--
Darren Dunham ddu...@taos.com
Unix System Administrator Taos - The SysAdmin Company
Got some Dr Pepper? San Francisco, CA bay area
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