Re: journal on an ssd

[Tobias Oetiker <tobi oetiker ch>]

Hi Andreas,
Today Andreas Dilger wrote:

> On Sep 11, 2008  07:43 +0200, Tobias Oetiker wrote:
> > You are telling me things that I am aware of. The reason I wrote to
> > this group is to figure what would happen to an ext3 fs when the
> > external journal was lost, especially what happens when it is lost
> > on a filesystem where 'data=journal' is set.
>
> Losing a journal will, in 99% of the cases, mean the loss of only a
> few seconds of data.  In some rare cases it may be that an inconsistency
> from a partially-updated commit will cause e2fsck to become confused
> and possibly clean up a small number more files than it would have
> otherwise.

glad to hear

> > Because if it is catastrophic, then it basically means that the
> > journal has to reside on a device that is as secure as to rest of
> > the data, meaning that if the data is on RAID6 then the journal
> > should be on RAID6 too.
>
> No, because RAID6 is terribly sucky for performance.  If you need this
> kind of reliability triple-mirrored RAID 1 would be better.  Much less
> CPU overhead, and no extra IO.

true ...

do you happen to know how zfs handles it when the intent log is on
an ssd ?

cheers
tobi

-- 
Tobi Oetiker, OETIKER+PARTNER AG, Aarweg 15 CH-4600 Olten, Switzerland
http://it.oetiker.ch tobi oetiker ch ++41 62 775 9902 / sb: -9900