> The amount of each component drive this is actually in use is stored - > in the default metadata - in a 32bit number as kilobytes. > This sets a limit of 4TB. > > The version-1 metadata format has a 64bit field. > > If you use mdadm 2.3, it will automatically select version-1 metadata > if you choose a size larger than 2TB (I think). > You might also need a very recent (16-rc) kernel for v.large raid1 to > work. There were bugs related to this usage pattern that were fixed > only recently. > > To avoid resyncing >4TB, use of a write-intent-bitmap is strongly > recommended. Thanks for the quick reply. I see now that mdadm supported the new version-1 metadata format as of 1.8.1, though that was labelled a devel release in its Announcement (also where the new metadata is mentioned). I do not see any mention of this in the Changelog however until 2.0, which allows you to specify the metadata type with the '-e' option. Also, the man pages for the 2.x releases state that the default metadata "limits arrays to 28 componenet devices and limits component devices of levels 1 and greater to 2 terabytes." So, I admit I am still confused. Either: 1) As you indicated, and I have seen myself, I can go up to 4TB with the default metadata on 1.11.0 which means the man pages for 2.x, the first to actually mention metadata, are incorrect. 2) mdadm-1.11.0 (which I am using), and possibly earlier, supported version-1 metadata, but it was not a selectable option within mdadm, but rather mdadm auto-selected metadata based on what options and sizes one threw at it. 3) Neither of the above, and I was just bloody lucky to be able to create an array that size, and anything beyond 2TB on mdadm 1.x is not a very good idea for production use. :) Again, thanks for the info, and if you have any further insight, I'd be grateful. -- Jeff Hardy Systems Analyst hardyjm at potsdam dot edu - 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
