> -----Original Message----- > From: dan.j.williams@xxxxxxxxx [mailto:dan.j.williams@xxxxxxxxx] On Behalf Of Dan Williams > Sent: Saturday, July 16, 2011 3:10 AM > To: NeilBrown > Cc: Naruszewicz, Maciej; Neubauer, Wojciech; Kwolek, Adam; Wojcik, Krzysztof; Ciechanowski, Ed; linux-raid@xxxxxxxxxxxxxxx > Subject: Re: [PATCH] mdadm.8: Disk coercion with IMSM metadata. > > On Wed, Jul 13, 2011 at 7:26 PM, NeilBrown <neilb@xxxxxxx> wrote: >> On Wed, 13 Jul 2011 12:17:02 +0200 "maciej.naruszewicz" >> <maciej.naruszewicz@xxxxxxxxx> wrote: >> >>> From: maciej.naruszewicz <maciej.naruszewicz@xxxxxxxxx> >>> >>> Actual sizes of disks from different producers may vary, >>> even though they are claimed to have the same amount of >>> space >> >> Are you sure about this? >> >> It was my understanding that some industry association has arranged an >> agreement so that this does not happen. >> >> http://www.idema.org/wp-content/plugins/download-monitor/download.php?id=1223 >> >> Do you have actual evidence that different drives from different >> manufacturers have similar but not identical sizes? >> > > Hmm, seemed to be a case that needed handling when requirements were > being gathered, but perhaps recent drives don't do this any more? > > Probably the more important part of this commit is that the man page > currently says that --size can not be used with container metadata... > but now that I have taken two seconds to think about it the light bulb > goes off... > > --size is indeed irrelevant for: > mdadm --create /dev/md/imsm /dev/sd[a-d] -e imsm > > but my first reading of comment was that: > mdadm --create /dev/md/vol0 /dev/md/imsm --size=$size > ...is somehow not valid. > > How about something like "For CONTAINER metadata --size is valid when > creating and growing subarrays, when creating a new container set > --size is irrelevant" > > -- > Dan > > Do you have actual evidence that different drives from different > manufacturers have similar but not identical sizes? > I'm afraid I do... For instance I have two disks, first one from Western Digital (model WDC WD2500YS-01SHB1), the second one from Seagate (model ST3250410AS). Both are said to have 250 GB maximum data space- however, the OS doesn't agree. LBA count for WD is 490234752, while for ST it's 488397168- that makes 251000193024 against 250059350016 bytes, nearly 1GB of difference! I'm not sure when those disks were produced- maybe newest disks are manufactured according to the IDEMA standard, but this example shows that there definitely are differences. > > How about something like "For CONTAINER metadata --size is valid when > creating and growing subarrays, when creating a new container set > --size is irrelevant" > Indeed, the --size option is irrelevant for containers and valid for subarrays in the container; however, the manpage stated: "This value cannot be used with .B CONTAINER metadata such as DDF and IMSM.". By "this", the author meant that "--grow --size" cannot be used, he / she didn't mean the "--size" alone. This sentence is deleted in the patch I sent earlier and explained more clearly in its description. Of course, we could add the information Dan mentioned to make it even more understandable. Best wishes Maciek _______________________________________________________________________________ Intel Technology Poland sp. z o.o. z siedziba w Gdansku ul. Slowackiego 173 80-298 Gdansk Sad Rejonowy Gdansk Polnoc w Gdansku, VII Wydzial Gospodarczy Krajowego Rejestru Sadowego, numer KRS 101882 NIP 957-07-52-316 Kapital zakladowy 200.000 zl -- 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
