On Thu, Dec 10, 2009 at 06:17:24PM -0500, nixlists wrote:
quoted text
> On Thu, Dec 10, 2009 at 6:00 PM, Marco Peereboom <slash@peereboom.us> wrote:
> >> Does this mean there's little advantage of hardware mirror raid over
> software?
> >> So software mirror raid increases chances of data corruption while
> decreasing
> >> the chances of downtime. True for hardware as well?
> >
> > There are pro and cons to both solutions.  Pick what makes sense in your
> > scenario.
> >
> >> Hmmm. I've used hardware raid cards for mirrors that have the verify
> function.
> >> It would be interesting to know how and what those cards do.
> >
> > They read the data to make sure the disk is working.  If one disk is
> > failed they can rebuild that block from the remaining disk provided that
> > the remaining disk isn't corrupt or broken too.  They assume that the
> > data that was read is accurate; if it isn't you are SOL.
> >
> > They either don't detect or ignore blocks that are different because
> > they can not know which one is accurate (if any).
> >
> > Verify for RAID 1 is mostly marketing fluff.
> 
> Thanks a lot for this info. In the past I've had weird corruption of
> files with a
> raid card - some files on the volume would become corrupt, but the
> corruption was limited
> to files only. IOW the whole volume would be intact and I could write
> and read new files to it
> but as the time went some individual files would contain garbage
> instead of real data. I wonder
> what that was all about.

probably a crappy card or disks.