On Fri, Oct 14, 2016 at 03:59:20PM +0200, Ramon Hofer wrote: > Still I would imagine if I assume that a bit per chunck is needed and I > use 128kB chuncks on the 11720662272 blocks of the 12TB RAID5 this is: > log(11720662272)/log(2) = 34 Bytes > > Or am I totally wrong? It's negligible, a few bytes in the metadata somewhere. The bitmap has its own size (--bitmap-chunk option). It's fine to set this to a large value (128MiB, 1GiB, ...). That might help performance and reduce the bytes required for the bitmap itself (not that it matters). The main issue is performance impact... it's a tradeoff for additional bitmap updates each write, or long resync time after a power loss or similar event. If performance is not critical (e.g. it's a NAS, not a database) then you can enable it without worries. Regards Andreas Klauer -- 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
