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Re: NetBSD on a database server - WAPBL, softdeps

On Sep 17, 2009, at 10:54 PM, Thor Lancelot Simon wrote:

On Fri, Sep 18, 2009 at 01:21:06AM +0100, Mindaugas Rasiukevicius wrote:
Thor Lancelot Simon <> wrote:

and keeping in mind softdeps are scheduled to be removed in 6.0
( ), what is the recommended configuration, filesystem wise, for a database server running on NetBSD? Wouldn't running with "bare" UFS be too slow?

Why would you expect any benefit from either WAPBL or soft updates on a database server? Databases (or, at least, any database worth using) manage their tablespaces independently, generally without creating or deleting files in the filesystem -- or doing so very seldom, if at all.

Are you suggesting that long boots after system failure is the option?

I'm suggesting that long boots after system failure *simply won't happen*
with sane disk layout and database design.  Even an FFS filesystem of
many terabytes will fsck very quickly if it contains only the very small number of directories and files that a properly designed database uses.

Databases journal their data themselves. They don't need help from the
filesystem to do it, generally speaking.

Mmm -- maybe. I think they need some way to ensure that certain blocks are flushed to the disk. This is, strictly speaking, not a filesystem issue, but something has to pass the request (from fsync_range()?) to the driver. I note that the MacOS F_FULLFSYNC command of fcntl() is only specified to exist for
a few file systems, at least on Leopard.

Other than that, I agree with your points completely.

                --Steve Bellovin,

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