On 04/11/15 21:30, Hugo Mills wrote: > On Wed, Nov 04, 2015 at 09:10:42PM +0000, OmegaPhil wrote: >> Back in September I noticed that 'sudo du -chs /mnt/storage-1' reported >> 887GB used and 'df -h' 920GB for this particular volume - I went on >> #btrfs for any suggestions, and balancing + defraging made no >> difference. It had no subvolumes/snapshots etc, I basically used it like >> a checksumed ext4fs. >> >> Since the volume was converted from ext4, I redid it from scratch (so >> made with kernel v4.1.3 or v4.1.6 on this Debian Testing machine), and >> the problem went away. >> >> After a couple of months, df reports 907GB used, whereas du says 884GB - >> I currently have 8 large (1-5.5TB volumes) btrfs volumes in use, >> storage-1 is the only SSD volume and the only one with this problem. >> >> No balancing or defraging this time, it didn't make a difference before >> and this is a relatively new volume. >> >> Are there any sysadmin-level ways I can account for the ~23GB lost space? > > There's an issue where replacing blocks in the middle of an > existing extent won't split the extent, and thus the "old" blocks > aren't freed up, because they're held by the original extent (even > though not actually referenced by any existing file). This might be > what you're seeing. > > I'm not sure how to confirm this theory, or what to do about it if > it's true. (Defrag the file? Copy it elsewhere? Other?) > > Two other cases for df > du are orphaned files, although 23 GiB of > orphans is large; and missing out the dot-files in the directory that > du is run from (if doing, say, "du *" rather than "du ."). I've been > bitten by both of those in the past. > > Hugo.
The volume doesn't change hugely over time, so it really ought not to have broken so quickly - a quick rundown of the storage usage: 36% general (small files, some smallish videos) 24% music 23% pr0n 17% VMs But in terms of 'large files changing', it could be the VM disks perhaps - I'll move them out, balance, and then back in again, hopefully that'd be a meaningful test. du-wise was direct on the root directory, any idea how I could audit orphan files? Thanks
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