[CentOS] CentOS 6.9, shredding a RAID

Wed May 31 16:02:36 UTC 2017
Valeri Galtsev <galtsev at kicp.uchicago.edu>

On Wed, May 31, 2017 10:39 am, Paul Heinlein wrote:
> On Wed, 31 May 2017, m.roth at 5-cent.us wrote:
>> I've got an old RAID that I attached to a box. LSI card, and the
>> RAID has 12 drives, for a total RAID size of 9.1TB, I think. I
>> started shred /dev/sda the Friday before last... and it's still
>> running. Is this reasonable for it to be taking this long...?
> Unless you specified non-default options, shred overwrites each file
> three times

With modern drives (read: larger than 100GB) writing the track over once
with anything will be sufficient. Overwriting multiple times with
different information was used awfully long ago when track had noticeable
width and distinct edge (drives were smaller than 1 GB then), thus it was
possible to distinguish narrow side of older record (using much more
sensitive equipment)) as newly recorded track is usually slightly shifted
with respect to old one, so narrow stripe of old one is not covered on one
side. These times are long gone, one can clean drives one at a time just
overwriting the whole device using dd (mind bs size to not impend speed).
Better though: physically destroy platters, it may take less of _your_
time to do that.

Just my $0.02


> -- and writing 27 TB to an old RAID array will be
> extremely slow. Also, shred has a builtin PRNG, and I'm not really
> sure how speedy it is.
> Still, 12 days seems like a really long time...
> --
> Paul Heinlein <> heinlein at madboa.com <> http://www.madboa.com/
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Valeri Galtsev
Sr System Administrator
Department of Astronomy and Astrophysics
Kavli Institute for Cosmological Physics
University of Chicago
Phone: 773-702-4247