On Mon, Nov 06, 2017 at 01:15:50AM -0200, Luciano ES wrote: > I have two 1TB disks, one of them on USB. The USB disk is supposed > to be a backup copy of the internal disk. > > I run this command: > > rsync -aSHxv --delete-before /xx/ /media/usbxx/ > > After all the copying, I get this output from df -h: > > Filesystem Size Used Avail Use% Mounted on > /dev/mapper/cxx 931G 520G 411G 56% /xx > /dev/mapper/usbxx 932G 529G 403G 57% /media/usbxx > > So the USB disk takes up 9GB more than the internal disk. > > Why? > > That is not a problem now, but will be when the disks are nearly full. > > I investigate: > > ---------------- 8< ---------------- > #> xfs_info /xx > meta-data=/dev/mapper/cxx isize=256 agcount=8, agsize=30506944 blks > = sectsz=4096 attr=2, projid32bit=1 > = crc=0 finobt=0 spinodes=0 rmapbt=0 > = reflink=0 > data = bsize=4096 blocks=244055552, imaxpct=25 > = sunit=0 swidth=0 blks > naming =version 2 bsize=4096 ascii-ci=0 ftype=0 > log =internal bsize=4096 blocks=119167, version=2 > = sectsz=4096 sunit=1 blks, lazy-count=1 > realtime =none extsz=4096 blocks=0, rtextents=0 > > #> xfs_info /media/usbxx > meta-data=/dev/mapper/usbxx isize=512 agcount=8, agsize=30523735 blks > = sectsz=512 attr=2, projid32bit=1 > = crc=1 finobt=1 spinodes=0 rmapbt=0 > = reflink=0 > data = bsize=4096 blocks=244189877, imaxpct=25 > = sunit=0 swidth=0 blks > naming =version 2 bsize=4096 ascii-ci=0 ftype=1 > log =internal bsize=4096 blocks=119233, version=2 > = sectsz=512 sunit=0 blks, lazy-count=1 > realtime =none extsz=4096 blocks=0, rtextents=0 > ---------------- >8 ---------------- > > Looks like the only difference between them is the isize. But both were > formatted with the exact same line: > > mkfs.xfs -f -b size=2048 -d agcount=8 /dev/target With different versions of mkfs. One is a old v4 format filesystem, the other is a v5 format filesystem which uses metadata CRCs, uses larger inodes, has a free inode btree, has ftype enabled on directories, etc.... > For the first time, I tried to introduce the -i size=256 option, > but mkfs.xfs is not having it: > > "Minimum inode size for CRCs is 512 bytes" > > Why not? They are the same size! Why do they have different inode sizes? Because the v5 format is enabled by default now and that requires 512 byte inodes. > Why is the external disk "wasting" space and how do I avoid that? Its not wasting space. If you want it to be identical to your old disk, then use "mkfs.xfs -m crc=0 ....", but I really don't advise that because you are using USB drives for your backups and they need all the silent corruption detection help they can get.... Cheers, Dave. -- Dave Chinner david@xxxxxxxxxxxxx -- To unsubscribe from this list: send the line "unsubscribe linux-xfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
