On Fri, 22 Apr 2011 19:37:40 -0700 Dan Williams <dan.j.williams@xxxxxxxxx> wrote: > On Sun, Apr 17, 2011 at 5:38 PM, NeilBrown <neilb@xxxxxxx> wrote: > > As has been mentioned elsewhere, mdadm only recognised IMSM arrays on > > machines with IMSM hardware. I'm not entirely happy about this and may well > > change it. > > I have trouble answering the "least surprise" question in this area. > > Is it more surprising to go into your BIOS, explicitly turn off raid > support and still see raid devices showing up? Is the "RAID support has been explicitly turned off" state visible from a running kernel? or is it indistinguishable from "platform does not have RAID support"? > > Or is it more surprising to take a raid array from a raid enabled > system to raid disabled system and wonder why things won't assemble? > > For safety I think it is better if mdadm not perform operations that > might be incompatible with the platform option-rom. But if you need > to recover to a usb attached drive, or some other > platform-incompatible configuration, you can use the environment > variable in a pinch. There are 3 interesting cases: create, assemble, examine. (grow might be interesting too, but for now it would be confusing). I am perfectly happy for 'create' to be arbitrarily hard if platform support is not available. One is unlikely to want to create an array in that case anyway. I think 'examine' should always show whatever it can, which is the case for 3.2.1. Possibly it should also give a warning about any difficulty that might be experienced in assembling the array. Assemble in the interesting case. The law of least surprise requires it to either work or give a good error message. Your suggestion that it possibly should not work in some cases seems defensible, so at least a very clear error message would be good. As for how to over-ride the default caution - I would prefer --force to achieve it rather than requiring an environment variable. I would possibly accept --force-platform (or similar) but I think --force should be sufficient. What think you? Thanks, NeilBrown -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
