Re: What do Events actually mean?

[Neil Brown <neilb@suse.de>]

On Saturday March 22, jpiszcz@lucidpixels.com wrote:
> 
> 
> On Sat, 22 Mar 2008, Peter Rabbitson wrote:
> 
> > Robin Hill wrote:
> >> On Fri Mar 21, 2008 at 07:01:43PM -0400, Bill Davidsen wrote:
> >> 
> >>> Peter Rabbitson wrote:
> 
> >           UUID : b6a11a74:8b069a29:6e26228f:2ab99bd0 (local to host Arzamas)
> >         Events : 0.183270
> >
> > As you can see it is pretty old, and does not have many events to speak of.
> 
> What do the 'Events' actually represent and what do they mean for RAID0,
> RAID1, RAID5 etc?

An 'event' is one of:
   switch from 'active' to 'clean'
   switch from 'clean' to 'active'
   device fails
   device is added
   spare replaces a failed device after a rebuild

I think that it all.

None of these are meaningful for RAID0, so the 'events' counter on
RAID0 should be stable.

Unfortunately, the number looks like a decimal but isn't.
It is a 64bit number.  We print out the top 32 bits, then the bottom
32 bits.  I don't remember why.  Maybe I'll 'fix' it.

> 
> How are they calculated?

   events = events + 1;


Feel free to merge this text into the wiki.

NeilBrown