(S)ATA performance in FBSD 6.2/7.0

[Alexander Leidinger]

Quoting Alan Amesbury <amesbury at umn.edu> (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.
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