Re: [9fans] ata drive capabilities

[erik quanstrom <quanstro@quanstro.net>]

> > from my understanding of how google do things, loosing a drive just
> > means they need to replace it.  so it's cheeper to let drives fail.
> > on the other hand, we have our main filesystem raided on an aoe
> > appliance.  suppose that one of those raids has two disks showing
> > a smart status of "will fail".  in this case i want to know the  
> > elevated
> > risk and i will allocate a spare drive to replace at least one of the
> > drives.
> >
> > i guess this is the long way of saying, it all depends on how painful
> > loosing your data might be.  if it's painful enough, even a poor tool
> > like smart is better than nothing.
> >
> I agree (plus I was just wrong about SMART at first), though I do  
> think your example above is about preventing downtime, not so much  
> data loss (Even without smart entirely, and all the disks come up  
> corrupt, we're all backed up within some acceptable window, right?)

i don't know.  if you lean that direction, then the only thing raid gives
you is reduced downtime.

i think of raid as reliable storage.  backups are for saving one's bacon in
the face of other disasters.  you know, sysadmin mistakes, misconfiguration,
code gone wild, building burns down — disaster recovery.

(and if my experience with backups is any indiciation, it's best not to
rely on them.)

but this thinking is probablly specific to how i use raid.  i imagine the
exact answer on what raid gives you should be worked out based on
the application.  for linux-type filesystems, e.g., raid won't save your
accidently deleted files.

- erik