[GLLUG] USB Backup Media

Marr marr at copper.net
Thu Feb 18 22:07:00 EST 2010


On Wednesday 17 February 2010 10:31:08pm Chick Tower wrote:
> I had considered buying an external hard drive that attaches via a USB
> port for backing up my PCs.  Then it occurred to me that I could do the
> same thing with flash drives, and they would be even more portable and
> would save me money.  I could probably get by with 4GB drives, but 8GB
> ones aren't much more expensive.  I know that the flash drives have a
> limited number of write operations before they fail.  Does anyone know
> if they fail completely, or if there are any warning signs before they
> fail?
>
> I figure, to minimize writes, I would tar the files to be backed up on
> some extra space, or another partition, on the PC's hard drive and then
> copy that file to the flash drive.  If a flash drive fails, I can just
> pop in another one in its place.  Does anyone see any drawbacks to using
> flash drives as backup media?

I've been using USB flash RAM drives for backups for almost 7 years now and 
have had no problems. But I use them for _incremental_ (hourly, in my case, 
started by a 'cron' job) backups, not full system backups. This way, I can 
never (in theory) lose more than 1 hour's worth of effort. A 256 MB USB flash 
RAM drive (formatted with an 'ext2' filesystem) for just this purpose is 
always connected to my primary PC.

I basically do what you've suggested -- make a tarball on the HDD and then 
copy it to the USB flash RAM drive. As Charles wisely suggests, you should 
checksum the 2 tarballs to help assure data integrity. A couple of 
simple 'md5sum' commands is all I use.

The first USB stick (Apacer 128 MB) worked fine for almost 5 years. I replaced 
it for a larger USB stick (Apacer 256 MB), not because of any failures or 
problems but because I was occasionally overflowing it (because I keep 12 
days of hourly incremental backups on the same USB stick -- older tarballs 
are automatically deleted by the full-system backup job).

As for failures in general, I can't offer much. The only USB stick I've had 
fail was an old SanDisk 'Cruzer Mini', way back in 2004. I never used it as a 
backup device, so it hadn't seen much use. It had been acting weird for a 
long time though, often not being consistently recognized when plugged in or 
not showing partitions properly/consistently. The final straw was when it 
failed a 'mke2fs' command to re-format it. The message was:

   Writing inode tables:  0/26
   Could not write 8 blocks in inode table starting at 5: Attempt 
      to write block from filesystem resulted in short write

I sent it in under the 2-year warranty and got a free replacement from 
SanDisk. The replacement has seen little use since then but, as far as I 
know, still works.

HTH....

Regards,
Bill Marr


More information about the linux-user mailing list