On 3/17/2005 8:23 PM Bob Johnson wrote:
On Thursday 17 March 2005 10:08 pm, Drew Tomlinson wrote:
Tagged queueing queues up multiple instructions for the drive simultaneously. The drive then attempts to sort them out and execute them in optimum order. Some drives that claim to support tagged queueing do not correctly do so, and don't perform well when it is used (and may lose data). If you set the queue size to one, as recommended in the passage you reference, then only one instruction will be issued to the drive at time, and it will behave like a drive without tagged queueing. It will do no harm to the drive. If the drive correctly implements tagged queueing, this will slow down the drive, but if it does not correctly implement it, then this may dramatically speed up the drive (and make it more stable). I have an external drive that manages 1.3 MBps transfers with queueing enabled, and 25 MBps transfers when I set the queue size to one.I posted this a while back and am still having the same problem. Can anyone offer any insight as to if the sbp man page suggestion about tagged queuing is something I should try? Is there any risk of screwing up my drives by trying this?
As for whether it will help your specific problem, I don't know, but I can't see how it would do any harm to test it.
Using the camcontrol utility, I found these drives were already set to "1"
blacklamb# camcontrol tags da2 -v (pass3:sbp0:0:0:0): dev_openings 1 (pass3:sbp0:0:0:0): dev_active 0 (pass3:sbp0:0:0:0): devq_openings 1 (pass3:sbp0:0:0:0): devq_queued 0 (pass3:sbp0:0:0:0): held 0 (pass3:sbp0:0:0:0): mintags 2 (pass3:sbp0:0:0:0): maxtags 255
blacklamb# camcontrol tags da3 -v (pass4:sbp0:0:0:1): dev_openings 1 (pass4:sbp0:0:0:1): dev_active 0 (pass4:sbp0:0:0:1): devq_openings 1 (pass4:sbp0:0:0:1): devq_queued 0 (pass4:sbp0:0:0:1): held 0 (pass4:sbp0:0:0:1): mintags 2 (pass4:sbp0:0:0:1): maxtags 255
Thus setting tagged queuing to "1" had no effect. Thanks again for your explanation. I sure wish I could solve this issue!
Thanks,
Drew
This issue is not specific to FreeBSD. Any OS that supports tagged queuing has problems with some drives.
- Bob
[...]
da2 and da3 are two IDE drives in a firewire enclosure. These are also the drives that come up "referenced" after restarting. What do these errors mean? How can I correct them? Is the following section from the sbp man page applicable to my situation?
Some (broken) HDDs don't work well with tagged queuing. If you have prob- lems with such drives, try ``camcontrol [device id] tags -N 1'' to dis- able tagged queuing.
Thanks for your help!
Drew
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