Backup to Thumb Drive

[Alan Dayley]

On Mon, Nov 3, 2008 at 8:16 AM, Dan Lund <situationalawareness at gmail.com> wrote:
> I'd definitely have to side with the external hard drive scenario.
> While USB thumbdrives are real nice for the size they have a limited
> lifespan and can lose data much easier than a hard drive from
> electromagnetic interference.
>
> I still prefer Linus Torvalds' quote, "Only wimps use tape backup:
> _real_ men just upload their important stuff on ftp, and let the rest
> of the world mirror it ;)"
> lol
>
> Thanks,
> Dan Lund

Flash is LESS susseptible to electromagnetic interference than hard
disk drives.  I have personally tested degaussing coils that
successfully erased hard drives but did nothing to flash storage
drives.  This is because hard disk drives use magnitism to store data
while flash uses capacitance, essentially.

Data retention of flash is at least 5 years and some manufacturers
state retention times much longer than that.  Sitting in a safe
deposit box enviornment, flash should not lose data.

But, it all depends.  ;^)

There are, generally, two types of flash: multi-level cell (MLC) and
single-level cell (SLC).  MLC can store two or more bits in a single
flash cell while SLC stores one bit per cel.  Most consumer flash
drives use MLC flash because it is MUCH cheaper than SLC.  But,
becuase of the mult-bit (read: multiple voltage level) nature of MLC,
it is far less data reliable than SLC.

The rub is that there is not an easy way to find out if the flash
device you have is MLC or SLC except by price.  SLC will be quite a
bit more expensive.  SLC is also sold under a description of
"industrial" or "high reliability" and such terms.  If what you have
was a good consumer price and does not have such terms attached to it,
it's MLC almost for sure.  This is not to say that MLC is all bad.  It
works well for situations like storing photos or operations where lots
of rewriting does not take place, like backups.  ;^)

Just remember, with flash media you DO get what you pay for.  Buy a
well known brand link San Disk, Lexar, STech, Samsung, Toshiba, etc.
to get the highest quality possible.  Don't skimp on price, especially
for data backup.  The "off brands" do buy up low quality or even
rejected flash for use.  This is usually not a big problem because if
a bit flips in one of 8 mega pixels of a photo, would you know it?
But if a bit flips in your ext2 filesystem inode tree, you may have
just lost something!

I would have no problem depending on flash to store backups as long as
I used the best quality drives I could find.  And they were in a
resonable refresh schedule like one would with tapes or hard drives
anyway.

Check Sam's Club.  They regularly have Toshiba USB sticks and other
flash media on sale for the price of bargan brands elsewhere.  They
are good quality, in my experience.

I love Linus' backup method too.  But I'm no Linus Torvalds so must
use other methods.

Alan