On 19 February 2011 04:49, NeilBrown <neilb@xxxxxxx> wrote: > On Sat, 19 Feb 2011 00:47:10 +0000 Mathias BurÃn <mathias.buren@xxxxxxxxx> > wrote: > >> Hi, >> >> >From the mdadm manual: >> >> "-b, --bitmap= >> [...] >> Note: external bitmaps are only known to work on ext2 and ext3. >> Storing bitmap files on other filesystems may result in serious >> problems." >> >> I was planning to store the external bitmap on an ext4 partition. Will >> this be a problem, or is the warning there because it hasn't been >> tested enough but no problems found? > > External bitmaps use 'BMAP' to find where the file lives on the device and > then writes directly to the device - not through the filesystem. > > So as long as there is no tail-packing to block migration happening it should > work fine. > > I haven't looked inside ext4 but I am fairly confident that external bitmaps > will work properly. > > NeilBrown > > Thanks, Neil. Are there any differences between using an internal or external bitmap? Also, does one need a bitmap at all when not planning to "mess" with the array? (does it provide any other purpose?) // Mathias -- 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
