gjournal: journaled slices vs. journaled partitions

[Carl]

Volodymyr Kostyrko wrote:

> I have some setups were gjournal was put on device rather the on 
> partition, i.e.:
> 
> [umgah] ~> gmirror status
>           Name    Status  Components
> mirror/umgah0  COMPLETE  ad0
>                           ad1
> [umgah] ~> gjournal status
>                   Name  Status  Components
> mirror/umgah0.journal     N/A  mirror/umgah0
> [umgah] ~> glabel status
>              Name  Status  Components
>    ufs/umgah0root     N/A  mirror/umgah0.journala
> label/umgah0swap     N/A  mirror/umgah0.journalb
>     ufs/umgah0usr     N/A  mirror/umgah0.journald
>     ufs/umgah0var     N/A  mirror/umgah0.journale

Does the above suggest that you've ended up with individual journal 
providers for each partition anyway? If so, where are they and have you 
really achieved anything functionally different? Are they at the end of 
their individually associated partitions or all together somewhere else? 
Has the ill-advised journaled small partition issue been successfully 
overcome through what you've done?

> [umgah] ~> mount
> /dev/ufs/umgah0root on / (ufs, asynchronous, local, noatime, gjournal)
> devfs on /dev (devfs, local)
> /dev/md0 on /tmp (ufs, asynchronous, local)
> /dev/ufs/umgah0var on /var (ufs, asynchronous, local, noatime, gjournal)
> /dev/ufs/umgah0usr on /usr (ufs, asynchronous, local, noatime, gjournal)
> devfs on /var/named/dev (devfs, local)
> 
> And yes, mirror autosynchronization is turned off, gjournal takes care 
> of that too.
> 
> It's not stated in manual, but gjournal is typically transparent for any 
> type of access, just in case of UFS file system is marked as journaled 
> so any metadata writes can be distinguished from data writes. Without 
> that gjournal does literally nothing.

And what does this mean for your swap partition?

Laszlo Nagy wrote earlier:
> Another tricky question: why would you journal a SWAP partition?

Volodymyr, does your assertion that gjournal does nothing when a file 
system is not UFS mean that there is no penalty with regard to your swap 
partition despite the existence of "mirror/umgah0.journalb"?

Any chance you'd like to share your command sequence for constructing 
your gmirror'd and gjournal'd filesystem, Volodymyr? :-)

Carl                                             / K0802647