Re: (S)ATA performance in FBSD 6.2/7.0

Quoting Alan Amesbury <amesbury@xxxxxxx> (Fri, 02 Mar 2007 17:56:04 -0600):

Looking at /usr/include/sys/mount.h, I see that there are two flags
defined: MNT_SYNCHRONOUS and MNT_ASYNC. I'm not sure why both flags
exist, but suspect the former was added so you could mount UFS/FFS/UFS2
filesystems that had soft updates enabled in synchronous mode without
having to umount the filesystem, use tunefs(8)'s "-n" flag to
enable/disable soft updates, then remount the filesystem with the
appropriate flag(s).

In FreeBSD we have 3 types, not 2. We have "sync", "noasync" (default)
and "async".

With noasync the meta-data is written in sync mode and the data is
written in async mode.

For async the complete IO is done asynchronous (the meta-data too).

And for sync the complete IO is synchronous.

mount(8) tells this with some more words.

Bye,
Alexander.

--
As a math atheist, I should be excused from this.
-- Calvin
http://www.Leidinger.net Alexander @ Leidinger.net: PGP ID = B0063FE7
http://www.FreeBSD.org netchild @ FreeBSD.org : PGP ID = 72077137
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