Re: ZFS with Linux: An Open Plea

Matt Mackall
2007-04-27T22:11:35Z

On Thu, Apr 26, 2007 at 10:21:02PM -0700, Valerie Henson wrote:
> On Wed, Apr 18, 2007 at 01:25:19PM -0400, Lennart Sorensen wrote:
> >
> > Does it matter that google's recent report on disk failures indicated
> > that SMART never predicted anything useful as far as they could tell?
> > Certainly none of my drive failures ever had SMART make any kind of
> > indication that anything was wrong.
>
> I saw that talk, and that's not what I got out of it. They found that
> SMART error reports _did_ correlate with drive failure.

In fact, a certain small set of SMART indicators were a very good sign
that a drive would fail.

> However, they found that the correlation was not strong enough to make
> it economically feasible to replace disks reporting SMART failures,
> since something like 70% of disks were still working a year after the
> first failure report. Also, they found that some disks failed without
> any SMART error reports.

Indeed, SMART registered no counts at all for most failures, so on the
whole, it can't be said that SMART can predict failures.

So: not a good idea to base your backup scheme on SMART warnings, but
not entirely useless.

--
Mathematics is the supreme nostalgia of our time.