[ale] Which large capacity drives are you having the best luck with?

[Pat Regan]

On Thu, 06 Jan 2011 01:51:28 -0500
Ron Frazier <atllinuxenthinfo at c3energy.com> wrote:

> BEFORE I FORGET - DO NOT USE SPINRITE ON AN SSD DRIVE.  They use
> totally different technology and writing to them excessively can
> substantially reduce the life of the drive.  Also, due to the wear
> leveling built in, I don't think an application can even be sure
> which memory sector it's writing to.  Data recovery benefit is
> questionable, surface analysis doesn't apply, and you may hurt your
> drive.

I would be very surprised if Spinrite can do anything useful on a
modern SSD.  Since SSDs are designed to be constantly relocating data I
wouldn't be the least bit surprised if they relocate on a bad read like
a SCSI/SAS drive would.  I have no proof of that, though, modern SSDs
use quite a bit of undocumented voodoo under the hood.

> That last sentence is not correct.  It may be true that Spinrite
> cannot calculate it's own ECC.  However, if the sector doesn't read
> correctly, the ECC correction is turned off.  Then, Spinrite reads
> the sector repeatedly, starting from different head positions and
> flying to the target sector, and accumulates up to 2000 samples of
> erroneous sector data.  It uses excruciating statistical techniques
> to analyze the samples and determine the most likely value, 1 or 0,
> for each bit.  It then reconstructs the sector and saves what it
> recovered back to the drive after a surface analysis has verified
> that it's safe to do so.  In many cases, just the repeated reading
> from different positions will accomplish a perfect read.  If so that
> perfect data is saved until a surface analysis verifies the magnetic
> reliability of the sector.

<snip>

> It may be slow, but if the one file that crashes is your critical
> program, database, or contract, that's still a problem.

The biggest problem is only having one copy of your critical program,
database, or contract.  :)

Knowing what I know about data recovery makes me nervous about using
recovered data files.

> That's possible.  I couldn't find any studies on it.  However,
> rewriting the data every 4 months eliminates the problem.  Now, you
> could debate endlessly about the cost vs benefits of doing that
> (spending time, etc) vs doing nothing.  Could probably write books
> about it.
> 
> For my purposes - "I don't want no bit rot invadin' my drives!"  Said
> while holding shotgun, etc. ;-)

A better use of your time and a safer option for your data would be to
keep good backups.  Most people have surprisingly little data that
truly needs to be backed up.  The most important personal data that I
need to back up regularly are my RCS repositories.  Nearly every
document and line of code I've written in the past 8 years or so is in
one of those repositories.  All of them lumped together are less than
200 MB.

My photographs take up quite a bit more room, but they're still
manageable.

Have we had a discussion here about backup strategies in the recent
past? :)

Pat