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Re: [Nmh-workers] some indexing results

From: Paul Vixie
Subject: Re: [Nmh-workers] some indexing results
Date: Tue, 15 Feb 2011 16:12:42 +0000

> From: address@hidden
> Date: Tue, 15 Feb 2011 10:42:34 -0500
> 00.21 versus 33.47?  I'd really investigate hot/cold cache effects
> there.  If you "just" moved it to UFS, a copy is probably still in
> cache.  Any way to flush the in-memory file cache on your box and
> try again?

there isn't but freebsd only has one buffer, inode, and metadata cache,
it's not per-filesystem.  and i ran those scans back to back, so if there
are caching effects going on then the second and third scans ought to be
equally fast for the two file systems.  it may be that rather than a
fragmentation problem there's a VFS flagging problem where ZFS is advising
the buffer cache not to keep copies of the metadata.  either way i'm going
to take a look at geom/gvinum.  i don't mind a write penalty for raid6/raidz2
but a read penalty of this many orders of magnitude is just too whacky.

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