gjournal: what is it good for?

[David N]

On 21 April 2010 18:52, Andrew Reilly <areilly at bigpond.net.au> wrote:
> On Wed, Apr 21, 2010 at 06:05:02PM +1000, David N wrote:
>> On 21 April 2010 12:48, Andrew Reilly <areilly at bigpond.net.au> wrote:
>> > On Wed, Apr 21, 2010 at 12:20:46PM +1000, David N wrote:
>> >> What kind of disks are you using? Or what hardware are you using?
>> >
>> > Several: main /usr is on a gjournal on top of a gmirror over a
>> > pair of Samsung 1TB 3.5" SATA drives, but I have other gjournals
>> > on a 750G WD SATA, a 1.5T Seagate and another 1TB WD MyBook
>> > firewire unit.  There is brokenness in the firewire connection
>> > that results in me always coming up manually through single-user
>> > mode, at the moment.  In single user mode pilot error is
>> > sufficient to account for the problems that I was having with
>> > mount vs fsck of the gjournalled drives, I'm fairly sure.
>
>> Wow, thats a setup.
>
> More an artifact of fair old age and accretion than design...
>
>> I have a few more questions.
>>
>> Your first email, you mentioned gjournal overflow panics. Have you fixed that?
>
> No: I've avoided it, at risk of incomplete backups, by leaving
> the -L (snapshot) option off my backup "dump" calls.  I'm fairly
> certain that I can generate those panics on demand, now that I
> know what's causing them.  (I prefer not to, of course, this
> machine is in constant use.)
>
>> I see you are gmirroring the slices, when you did the gmirror +
>> gjournal slice, did you check the bsdlabel? sometimes it doesn't
>> report the right block size, and the disk + journal overlap. I had
>> this happen to me on my first setup which resulted in the overflow
>> panics.
>
> Not sure about that.  All of my disks only have one bsdlabel, on
> the raw provider.  I fdisk -BI; bsdlabel -w -B and then newfs
> the ...s1a partition, as a general rule.  Now that I'm running
> gjournal, that's fdisk; bsdlabel; gjournal label ...; newfs
> ...s1a.journal.  There isn't a label between the gjournal and
> the file system.
>
> In the case of my main, gmirrored disk pair, I bsdlabel -e'd
> after the "use whole disk" standard procedure and made liberal
> use of "*" wildcards to make sure that bsdlabel did the right
> thing.  I was *very* glad when I didn't have to muck about
> calculating sector offsets any more.
>
> I have my mirror'd pair layered: fdisk; bsdlabel; gmirror on
> ad[46]s1a, ad[46]s1d and ad[46]s1e, separately, rather than
> mirroring the raw ad4/ad6 pair and then bsdlabeling the
> resulting mirror because I couldn't see the point in swapping to
> a mirror.  So I swap to ad4s1b and ad6s1b independently.  So I
> have root on mirror/gm0a (no soft-updates), var on mirror/gm0d
> (with soft-updates), and a gjournal on mirror/gm0e, with a newfs
> -J partition on mirror/gm0e.journal
>
>> Its not as easy as a
>> gmirror label ...
>> gjournal label ...
>> You gotta check the bsdlabel each time to make sure the c slice and
>> additional slices are the correct size.
>
> I didn't think that GEOM layers needed to have a bsdlabel each,
> and newfs is happy enough (I think) to sit on an unlabelled GEOM
> provider.  Certainly the examples in the gjournal, gmirror and
> mdconfig man pages seem to suggest that newfs'ing straight onto
> one of them is the way to go.
>
>> If you do decide to do it again, gpt made it really easy.
>
> What's a gpt?  Neither man nor bash know about it on my system.
>
>> Did you use newfs -J to format the slices/journal?
>
> Yup.
>
> Thanks for the help and suggestions!
>
> Cheers,
>
> --
> Andrew
>

Can you show me a print out of
gjournal list
and
bsdlabel /dev/mirror/gm0e.journal

And any other .journal you have

Just want to double check something.

Regards
David N