[ale] what exactly does a long smart hdd test do?

[mike at trausch.us]

On 05/14/2012 01:38 PM, Ron Frazier (ALE) wrote:
> You mention data scrubbing in your post. I've run across that in my
> research, as well as some very interesting info on latent defects. My
> research is ongoing, but my current conclusion is that data scrubbing is
> beneficial for personal drives too, hence my willingness to run 36 - 48
> hours of diagnostics on my drives, 2 - 3 times / year. Data scrubbing
> may be more valuable on personal drives than on raid, since there is no
> drive to auto failover to. If the sectors on my drive fail to read,
> unless SpinRite can recover them, which I've seen it do on occasion,
> then my only solution is to resort to backups, which are probably out of
> date.

I don't see the need to scrub on personal drives.  Personal drives
should not require lots of time to manage.  Same goes for workstation
drives.

Scrubbing on a RAID array is absolutely essential for the early
detection of failures that will cause the RAID array to degrade.  That
scrub ensures that every drive's every sector is legible.  Errors will,
of course, mostly be detected during that time.  The point of the scrub
is to find errors in parts of the disks that haven't been accessed
regularly since the last scrub, which is a vast majority of the disks'
surfaces in most systems.

I do think, though, that the interval is probably better at six weeks.
I haven't made that change yet, but since a scrub is stressful on the
system it does reduce life.  Doing only 8 per year as opposed to 12
probably wouldn't make much difference, though, and I haven't the time
or the money to test this empirically with any statistical relevance.

	--- Mike

-- 
A man who reasons deliberately, manages it better after studying Logic
than he could before, if he is sincere about it and has common sense.
                                   --- Carveth Read, “Logic”

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