When a hard-drive controller detects an error, and needs to remap a sector, the drive normally becomes unresponsive for the seconds (or possibly minutes) it takes to try to complete the re-mapping.

With the drive no longer responding, a host RAID controller can assume that the drive has failed, and mark it as unreliable.

Some hard-drive models, from some manufacturers, have a feature to limit (in seconds) how long the drive will spend trying to remap a sector. Different drive manufacturers give different names to this feature:

Note: The correct term from the ATA/ATAPI command set is Command Completion Time Limit (CCTL)

By limiting the time the drive spends trying to recover a sector, it ensures that the host RAID controller will not think that the drive has failed.

Different RAID controllers (hardware and software) have different timeout intervals. If the drive is unresponsive for longer than their timeout it will be marked as offline, e.g.:

On to my question

Is there an option in Windows that controls how long Windows will wait before it decides a drive is not responding?

i do know of a registry setting called TimeoutValue:


  • TimeoutValue
    • Location: HKLM\System\CurrentControlSet\Services\Disk\TimeoutValue
    • Values: 1 - 255 seconds
    • Meaning: Time in units of seconds before an SRB request initiated by the disk class driver will time out. If this registry value is not set, a default value of 10 seconds is used. Time-out values for requests that are initiated by class drivers vary according to the class driver.
    • Operating system version: This feature is available in all versions of the Windows operating systems.

But this is only documented as applying to the SCSI Miniport Driver. And even if it also applies to my SATA drives, it doesn't guarantee that it also applies to Window's RAID-5 subsystem.

The reason i ask about adjusting the timeout in my (software) controller is because hard-drive manufacturers have started to get mean-spirited:

  • no longer including the ability to limit the error-recovery time
  • they intentionally lock one feature of the ATA/ATAPI command set behind a pay-wall.

For that firmware feature they want you to buy the more expensive ("RAID Edition") drives (e.g. 71% more expensive). Thus changing:

Bonus Reading

See also

1 Yes, inexpensive. Source: "A Case for Redundant Arrays of Inexpensive Disks (RAID)", D.A. Patterson, G. Gibson, and R.H. Katz, ACM SIGMOD Conference, June 1988, Chicago IL.

  • 1
    Just a nit picky note... RAID has not referred to inexpsensive disks for a while now... but rather independant disks. en.wikipedia.org/wiki/RAID. Also, to clarify are you using the built-in Windows (software controller) RAID functions as opposed to a hardware card? – Brent Pabst Aug 6 '12 at 16:48
  • @BrentPabst Yes. – Ian Boyd Aug 6 '12 at 20:18

This doesn't really answer your question per se, but as a recommendation software RAID controllers, in my experience, are far less reliable than hardware controllers. If you have the budget for them always opt for a stand-alone card to take the burden of disk IO off of the computer itself.

  • i'm concerned that if the card itself fails, the entire array is lost. i presume a RAID controller card from one manufacturer is incompatible with a raid controller card from another manufacturer, is incompatible with Microsoft's software solution. At least with a Windows software solution i am guaranteed future compatibility. And when it comes to data safety, confusion and fear is not something i want to have to deal with. – Ian Boyd Aug 7 '12 at 21:39
  • True... but if anything happens to your Windows installation your data could be lost as well. You can also find redundant controllers or better yet just get a stand-alone DASD to connect to your server, it will have by far the best redundancy compared to either solution. All a matter of how much money you want to throw at it versus how much money you can lose if it goes down. – Brent Pabst Aug 7 '12 at 21:43
  • Problem with a separate device is that if it dies then i lose all data. At least now i don't lose data. – Ian Boyd Aug 8 '12 at 14:04
  • True, but the same could be said of your Windows installation. You still have a single point of failure any way you look at it. At least the mean-downtime of a physical storage device is much higher than a server (ent. devices of course) – Brent Pabst Aug 8 '12 at 15:42
  • i'm not sure what you mean by my "Windows installation" is a point of failure. If my Windows installation fails i can put in a Windows Server DVD, and 37 minutes later i have access to my data again. If my Promise FastTrack 66 card dies i (probably) lose my data. – Ian Boyd Aug 11 '12 at 15:41

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