On 19 February 2011 12:14, Roman Mamedov <rm@xxxxxxxxxx> wrote: > On Sat, 19 Feb 2011 04:55:32 +0000 > Mathias BurÃn <mathias.buren@xxxxxxxxx> wrote: > >> > 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?) > > I have successfully stored an external bitmap on XFS for a brief time. > However it proved difficult to ensure that the device storing the bitmap is > mounted, accessible and writable prior to boot scripts attempting to run the md > arrays, so since then I just switched to an internal bitmap. The negative > performance it had can be minimized to almost zero by using a larger bitmap > chunk size. > > -- > With respect, > Roman > I ended up storing the bitmap on my root filesystem (ext4) for now. It's currently at the default size but I think I'll recreate it with 64MB size. // 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
