On Sat, Dec 17, 2011 at 05:35:15PM +0100, Martin Steigerwald wrote: > Am Samstag, 17. Dezember 2011 schrieb Hugo Mills: > > > I might still be doing the balance for that optical viewing pleasure > > > ;). > > > > :) > > > > It can't hurt, and with such a small FS it probably won't take > > long. > > Now I first did a defrag and then a balance. The balance was heavier I had > music stalls of about 5 to 10 seconds at time. > > The defrag aborted quickly with a non-zero return code on second run: > > deepdance:~> btrfs filesystem defragment / > ^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C > > I wanted to start it via time. > > deepdance:~> /usr/bin/time btrfs filesystem defragment / > Command exited with non-zero status 20 > 0.00user 1.26system 0:03.86elapsed 32%CPU (0avgtext+0avgdata > 2160maxresident)k > 2656inputs+70712outputs (2major+184minor)pagefaults 0swaps > > Nothing in dmesg. Does 20 as return code mean "already defragmented"? ;) I'd have to check what return code 20 means, but... btrfs fi defrag is *not* recursive, so what you did is effectively a no-op anyway. > I am looking forward to the new asynchronous defrag interface I read about > somewhere. > > Current state now is: > > deepdance:~> btrfs filesystem df / > Data: total=7.75GB, used=6.91GB > System, DUP: total=8.00MB, used=4.00KB > System: total=4.00MB, used=0.00 > Metadata, DUP: total=896.00MB, used=506.47MB > > Lets see how that fares. > > Balance did log something: > > [24065.740937] btrfs: found 4207 extents > [24075.581494] btrfs: found 4207 extents > [24077.982099] btrfs: relocating block group 24465375232 flags 1 [snip] > [24730.473343] btrfs: found 19754 extents > [24735.912210] btrfs: relocating block group 20707278848 flags 36 > [24852.827906] btrfs: found 26482 extents > [24853.838002] btrfs: relocating block group 20698890240 flags 34 [snip] > Appears quite fragmented to me, but as I do not understand whats exactly > behind this numbers I leave it as it. The long numbers are block group IDs. These correspond to a position in the FS's internal address space (which doesn't, in the general case, map directly to anything -- there's an internal tree that holds the map). The flags indicate what type of block group is being moved. These correspond to the line headings in "btrfs fi df", and are a bitmap. "flags 1" is a non-RAIDed data block group. "flags 34" is a DUP system block group, and "flags 36" is a DUP metadata block group. You'll probably find a single reference to a block group with flags 2, which is the vestigial non-RAID System group you can see in your "btrfs fi df" output above. Extents are simply contiguous regions of storage, corresponding to parts (or all) of a file, or to individual tree blocks (which are 4k in size). The "found <N> extents" messages just indicate how many extents there are to move in the block group it's currently looking at. Hugo. -- === Hugo Mills: hugo@... carfax.org.uk | darksatanic.net | lug.org.uk === PGP key: 515C238D from wwwkeys.eu.pgp.net or http://www.carfax.org.uk --- "I lost my leg in 1942. Some bastard stole it in a --- pub in Pimlico."
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