Russell Coker posted on Sun, 11 May 2014 19:43:16 +1000 as excerpted: > Below is the output of running a balance a few times on a 120G SSD. > > It seems that whenever I set the metadata usage to be greater than 0 it > will report relocating something, regardless of whether that's possible.
Why would it be impossible? It's certainly not impossible from the information posted. As Brendan suggests, depending on the amount of metadata present, it's entirely possible that you have enough to fill X whole metadata chunks, plus under 10% and possibly under 1% of the next chunk, such that repeatedly running -musage=10 or -musage=1 will repeatedly balance that last chunk. Also, not being a dev I don't normally read code to know whether this is an issue or not, but given that btrfs will inline small enough files in the metadata, it's theoretically possible that a balanced state where more than one metadata chunk remains less than 100% full, if the inlined file data doesn't line up to exact chunks. Then of course there's the dup or raid1 metadata case (dup being the normal single-device metadata default, except if ssd is detected, raid1 being the multi-device metadata default in all cases), such that all metadata chunks are duplicated, effectively doubling the number of chunks rebalanced since each one has two copies. -- Duncan - List replies preferred. No HTML msgs. "Every nonfree program has a lord, a master -- and if you use the program, he is your master." Richard Stallman -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
