Western Digital hard disks and ATA timeouts

Jeremy Chadwick koitsu at FreeBSD.org
Fri Nov 7 00:36:30 PST 2008

On Fri, Nov 07, 2008 at 12:08:01AM -0800, Artem Belevich wrote:
> > Note that Western Digital's "RAID edition" drives claim to take up to 7
> > seconds to reallocate sectors, using something they call TLER, which
> > force-limits the amount of time the drive can spend reallocating.  TLER
> > cannot be disabled:
> TLER can be enabled/disabled on recent WD drives (SE16/RE2/GP). SE16/GP
> come with TLER off, RE2 with TLER on. Google WDTLER utility.
> It can apparently be obtained from WD by asking them nicely.
> Or, yet again, google is your friend. Here's one example -
> http://www.hardforum.com/archive/index.php/t-1191548.html

Thanks for the information.  Nice to know one of their FAQ entries is
false.  Also, note that "SE16/RE2/GP" is not specific enough; I have
SE16 drives from 2005, and I highly doubt those have TLER capability
due to their age.

Also, there's a Wikipedia article on this whole fiasco.


It also appears Samsung drives have a similar feature called CCTL,
which uses a value of 7 or 8 seconds:


But regardless of TLER being toggleable, FreeBSD's ATA command timeout
of 5 seconds is too aggressive, and should be increased.  Likewise, the
value should be a sysctl, so those who do want such aggressive values
can use it at the community's -- or their own -- behest.

| Jeremy Chadwick                                jdc at parodius.com |
| Parodius Networking                       http://www.parodius.com/ |
| UNIX Systems Administrator                  Mountain View, CA, USA |
| Making life hard for others since 1977.              PGP: 4BD6C0CB |

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