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Glen Pitt-Pladdy :: Blog

USB gets SMART

I previously had a rant about USB drives not having SMART. They still don't have standardised support, but the good news is that recent versions of smartmontools know enough about popular USB-ATA chips that they can get commands through to the disk on the other side of the chip and interrogate the SMART.

With Ubuntu version 5.41+svn3365-1 from Oneiric (the source packages builds perfectly under Lucid) all of my USB drives / adaptors work without any special options.

Sleeping on the job

The one thing when running any significant tests with these drives is that they will go to sleep when left alone and that will abort the test. The trick I came up with was to do a very slow read of the disk while running any long tests - that way it prevents the drive going to sleep, but doesn't disrupt the test.

Simply use cpipe with a low (1KB/s) speed limit:

$ sudo dd if=/dev/sdX | cpipe -s 1 >/dev/null

That should be enough to stop drives going to sleep during tests.

Hot stuff

The interesting thing with having access to the SMART data now is to see that is going on inside the enclosure. The drives do indeed run very hot inside their enclosures. Keep in mind that this is winter with the air temperature indoors is around 18C indoors. The 3 drives I use:

  • Plastic case major brand: 54°C (has reached 60°C previously)
  • Plastic case different major brand: 52°C (has reached 57°C previously)
  • Aluminium case less popular brand: 48°C (has reached 51°C previously)

Interestingly only the first drive has a SMART threshold for temperature and it's set at 55°C - ie. it's already been past that and runs near the threshold even in cooler air temperatures.

You can easily add 10°C for a hot summers day, much more in hot parts of the world, plus some thrashing to warm the disks up and things could be getting much hotter in those plastic cases. Fortunately these drives are in a cool environment and don't get heavy use so they have done relatively well. None the less it is concerning that they run so hot.

The other thing that strikes me is that the more expensive major brands are using funky looking plastic cases that are running distinctly hotter than the aluminium extrusions popular with lesser brands. Is this a case of style over engineering and reliability?

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