| Hello!
>1) Do you need to do anything other that associate a sub-disk with each plex
of
>a mirrored volume as stated in section 10.1.4 to enable bcl.
That's right, to enable BCL you need to create 2 subdisks of at least
1 sector in length and associate them with 2 plexes of your mirrored
volume. That's it. Once enabled, if you do a 'volprint -m <volname>',
you should see logging=on.
(FYI, in the next major release of Digital UNIX, BCL will be replaced by
DRL, dirty region logging. It's the same idea, just an improved
logging strategy that will require a 2 sector long logging subdisk.
So, if you plan to upgrade your system to the next major release and
still want logging, you should go ahead and create 2 sector long logging
subdisks and we will have migration tools that will handle the
conversion between logging strategies for you (of course, you'll need
to read the documentation to make sure you will be making the best use
of DRL). If you do use 2 sectors for your logging subdisks now, BCL
will continue to use 1 sector as always. You can set the size to
whatever you want, but BCL only uses 1 sector. I see that you're
running 3.2g. V4.0 still uses BCL. The next release will use
DRL. Just something to keep in mind.)
>2) Should the associated sub-disks be on physically different devices from
the
>plexes being mirrored or can it be on the same device as the plex it is
>associated with.
Every write to the mirrored volume will first be logged and then
written to the plex's underlying disks. You don't want that much contention
on one disk. So, because the logging subdisk is written to frequently, you
should put it on a disk that's not heavily used and avoid the disk seeking
back and forth between the log area and the data area during writes.
>3) Can you use bcl on mirrored system disks?
Well, you don't need BCL on swapvol (don't resync swap) so it provides
no benefit. You can set it up rootvol and it should work. Let me confirm
that there are no issues in this area and I'll get back to you.
Hope this helps!
[Posted by WWW Notes gateway]
|
| > 3) Can you use bcl on mirrored system disks?
Yes, but there's a known problem with BCL recovery on root when all
the logging subdisks fail, so I would suggest either placing root's
logging subdisks on the same disks as root's plexes (i.e., the boot
disks) or avoid using BCL on root for now. See qar 46428 for more
details.
--steve
[Posted by WWW Notes gateway]
|