On Thu, Apr 16, 2009 at 10:13:42AM -0400, James Smart wrote: > However, for arrays, with multiple luns, the queue depth is usually a > target-level resource, > so the midlayer/block-layer's implementation falls on its face fairly > quickly. I brought this If the problem were as simple as the resource being target-level instead of LUN-level, it would be fairly easy to fix (we could do accounting per-target instead of per-LUN). The problem, AIUI, is multi-initiator where you can't know whether resources are in use or not. > up 2 yrs ago at storage summit. What needs to happen is the creation of > queue ramp-down > and ramp-up policies that can be selected on a per-lun basis, and have > these implemented > in the midlayer (why should the LLDD ever look at scsi command > results). What will make > this difficult is the ramp-up policies, as it can be very target > device-specific or configuration/load > centric. While not disagreeing that it's complex, I don't think putting it in the driver makes it less complex. I completely agree that LLDDs should not be snooping scsi commands or scsi command results. It should all be in the midlayer so we all share the same bugs ;-) -- Matthew Wilcox Intel Open Source Technology Centre "Bill, look, we understand that you're interested in selling us this operating system, but compare it to ours. We can't possibly take such a retrograde step." -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
