On 13/12/13 09:13, Duncan wrote: > Martin posted on Thu, 12 Dec 2013 13:39:00 +0000 as excerpted: > >> Some time back, I noticed that with a two HDD btrfs raid1, some tasks >> suffered ALL the IO getting choked onto just one HDD! >> >> That turned out to be a feature of the btrfs code whereby a device is >> chosen depending on the process ID. For some cases such as in a bash >> loop, the PID increments by two for each iteration and so only one HDD >> ever gets hit... > > Unfortunately, yes... > ... Of course that's if the queue > length is reasonably accessible to btrfs, as you already asked in the bit > I snipped as out of my knowledgeable reply range. And that's the bit that is outside of my knowledge... Hence the question. Here's hoping someone can give a pointer before I need to delve into other code such as for 'atop' to see how it is done there if I'm to take a stab at it. Or if someone is already coding something up, please let us know? Or: >From within btrfs code, is there an easy/fast/any way to check the IO queue length for whatever btrfs target device? Regards, Martin -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
