Messages in this thread | | | Subject | Re: [RFC PATCH] block: Change default IO scheduler to deadline except SATA | From | "Martin K. Petersen" <> | Date | Wed, 11 Apr 2012 12:25:15 -0400 |
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>>>>> "Mike" == Mike Snitzer <snitzer@redhat.com> writes:
Mike> I'm not aware of any discrete attribute (comparable to Mike> 'rotational' flag) that SCSI devices will advertise that indicates Mike> "I'm a raid array".
Sadly, no.
Mike> That said, we can have a _very_ good hint that a SCSI device is a Mike> raid array if:
Mike> 1) optimal_io_size is not zero, minimum_io_size is not equal to Mike> optimal_io_size, and optimal_io_size is a multiple of Mike> minimum_io_size
Unfortunately there are still a lot of arrays out there that don't export the relevant VPDs.
I know there's a lot of resistance to doing stuff in the kernel that can be done in udev. But with my distro hat on we update the kernel much, much more frequently than we update udev rules. For a multitude of reasons.
Also, when it comes to disk arrays we already have a significant portion of them hardwired in the kernel anyway (quirks, LUN discovery, device handlers). So I'd personally be fine with having a BLIST_ARRAY flag that we could trigger off of.
-- Martin K. Petersen Oracle Linux Engineering
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