[geeks] Solaris 10 / OpenSolaris bits to be in next version of OSX

[Jonathan C. Patschke]

On Wed, 9 Aug 2006, Phil Stracchino wrote:

> Ooh.  I like the self-healing-data aspect.  I think that's worth
> violating a few abstraction barriers to get, as long as nothing gets
> functionally broken in the process.

Except that there's no reason to break down the barrier between volume
manager and filesystem to get there.  Set some blocks aside for
checksums in the volume manager, and you have the same functionality.

For instance, AIX has been doing things like this for years.  -Every-
slice lives inside a volume group managed by the LVM.  If you have a
volume group stating that there will exist more than one copy of each
block, AIX will -tell you- if/where a bad block comes into play, return
data from the good block, and deactivate the bad block.  This isn't new,
and AIX doesn't have separate maintenance tools, mount tables, and
nethodologies for dealing with filesystems guarded by the LVM in this
fashion.

The added bonus to the AIX approach is that you get this for -all-
slices, including paging slices.  It's Nice when you can replace a device
holding your page slice without rebooting the system.

The more sinister side of this is how Sun is selling it.  "Silent data
corruption"?  What in the world is that supposed to mean?

Data corruption does not happen unless there is a bug in the stack of
code somewhere between fread() and the SCSI transaction or unless the
hardware is defective.  There's nothing silent about it.  Either
hardware or software has failed; this is the general case for a failure
in a RAID metadevice.   So Sun's RAID implementation can handle that
scenario?  Well, uh, great.  That's rather why we have RAIDs in the
first place, isn't it?

If Sun is trying to say that their RAID software can handle errors not
directly derived from hardware failures, they might want to rethink the
implications of that statement before waving it about on a banner.

-- 
Jonathan Patschke    )   "A man who never dreams goes slowly mad."
Elgin, TX           (      --Thomas Dolby, "Valley of the Mind's Eye"