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Re: [dm-devel] [PATCH 1/3] Send KOBJ_ADD event after dm resume ioctl.



On Fri, Mar 19, 2010 at 11:55 AM, Mike Snitzer <snitzer redhat com> wrote:
Thing is, this isn't scalable at all.  Having all these arbitrary rules
issuing IOs to devices that aren't usable is a complete waste of time.
On enterprise systems that have 100s (*shudder* 1000s) of LUNs, this
udev rules' freedom to access such unusable devices is really working
against us (if the goal is to activate devices as quickly and reliably
as possible).

Please, Mike, whether to probe devices or not is a separate discussion
and it's not really helpful to reiterate that discussion.

(Please do see various mailing lists archives for that particular discussion;
FWIW, you will notice that what udev is doing is actually desirable. If you
examine the kernel sources, you will find that the kernel itself submits
IO to the block devices - partition table probing for starters. If you search
harder you will find *raw numbers* (instead of speculation like "100s
(*shudder* 1000s)" showing what udev is doing is not a problem...)

    David


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