Re: Regarding Filesystems

[Oliver Fromme <check+k4q2c000rswds2e3@xxxxxxxxxx>]

Matthew Dillon wrote:
 > [about FreeBSD's gjournal]
 >    It's kinda similar to DragonFly's VFS journaling... I built it but
 >    as far as I know only one or two people actually use it in production,
 >    and I'm not one of them.  The use cases are very limited.

Some time ago I played a bit with DF's journaling inside
a qemu instance, because I was curious how it works.
But I didn't do anything serious with it.

At the beginning I was a little confused about the various
terms used by DragonFly.  The main purpose of what DF calls
"journaling" seems to be replication, which is different
from what other operating systems call journaling.

On the other hand, the "mirroring" feature in HAMMER is
not really a RAID-1 (which is what people usually mean
when they talk about a mirror in the context of storage).
It is rather a replication mechanism, too, not completely
unlike DF's VFS journaling.

So, in other words, DragonFly now supports two different
FS replication features, one of them is called journaling
and the other is called mirroring, while it is neither
really the one or the other.  :-)

(Please don't take this as criticism.  I'm just trying to
explain my confusion.)

Best regards
   Oliver

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