[Galaxy Note 10.1 (2014 Edition) Android Developmen] epithetic:
Okay, so going through the factory image rigmarole doesn't seem to have resolved the internal storage weirdness, nor did messing with the options in recovery. On stock 5.1.1 "system" reports taking up almost 14GB in Settings/Storage, which seems... not right? Available space is roughly the same. This is what my partitions look like, back on temasek CM13:

root@lt03wifi:/ # df
Filesystem 1K-blocks Used Available Use% Mounted on
tmpfs 1422200 76 1422124 1% /dev
none 1422200 12 1422188 1% /sys/fs/cgroup
tmpfs 1422200 0 1422200 0% /mnt
/dev/fuse 18961108 2052492 16908616 11% /mnt/runtime/default/emulated
/dev/fuse 18961108 2052492 16908616 11% /mnt/runtime/read/emulated
/dev/fuse 18961108 2052492 16908616 11% /mnt/runtime/write/emulated
/dev/block/mmcblk0p20 2427060 1299192 1127868 54% /system
/dev/block/mmcblk0p3 20144 6400 13744 32% /efs
/dev/block/mmcblk0p19 761968 13160 748808 2% /cache
/dev/block/mmcblk0p21 18961108 2052492 16908616 11% /data

root@lt03wifi:/ # mount
rootfs on / type rootfs (ro,seclabel,relatime)
tmpfs on /dev type tmpfs (rw,seclabel,nosuid,relatime,mode=755)
devpts on /dev/pts type devpts (rw,seclabel,relatime,mode=600)
none on /dev/cpuctl type cgroup (rw,relatime,cpu)
proc on /proc type proc (rw,relatime)
sysfs on /sys type sysfs (rw,seclabel,relatime)
selinuxfs on /sys/fs/selinux type selinuxfs (rw,relatime)
/sys/kernel/debug on /sys/kernel/debug type debugfs (rw,seclabel,relatime)
none on /sys/fs/cgroup type tmpfs (rw,seclabel,relatime,mode=750,gid=1000)
none on /sys/fs/cgroup/bfqio type cgroup (rw,relatime,bfqio)
none on /acct type cgroup (rw,relatime,cpuacct)
tmpfs on /mnt type tmpfs (rw,seclabel,relatime,mode=755,gid=1000)
/dev/fuse on /mnt/runtime/default/emulated type fuse (rw,nosuid,nodev,noexec,noatime,user_id=1023,group_id=1023,default_permissions,allow_other)
/dev/fuse on /mnt/runtime/read/emulated type fuse (rw,nosuid,nodev,noexec,noatime,user_id=1023,group_id=1023,default_permissions,allow_other)
/dev/fuse on /mnt/runtime/write/emulated type fuse (rw,nosuid,nodev,noexec,noatime,user_id=1023,group_id=1023,default_permissions,allow_other)
/dev/block/mmcblk0p20 on /system type ext4 (ro,seclabel,relatime,errors=panic)
/dev/block/mmcblk0p3 on /efs type ext4 (rw,seclabel,nosuid,nodev,noatime,journal_checksum,journal_async_commit,noauto_da_alloc,data=ordered)
/dev/block/mmcblk0p19 on /cache type ext4 (rw,seclabel,nosuid,nodev,noatime,journal_checksum,journal_async_commit,noauto_da_alloc,errors=panic,data=ordered)
/dev/block/mmcblk0p21 on /data type ext4 (rw,seclabel,nosuid,nodev,noatime,journal_checksum,journal_async_commit,noauto_da_alloc,errors=panic,data=ordered)
tmpfs on /storage type tmpfs (rw,seclabel,relatime,mode=755,gid=1000)
/dev/fuse on /storage/emulated type fuse (rw,nosuid,nodev,noexec,noatime,user_id=1023,group_id=1023,default_permissions,allow_other)

root@lt03wifi:/ # cat /proc/partitions
major minor #blocks name

179 0 30535680 mmcblk0
179 1 4096 mmcblk0p1
179 2 4096 mmcblk0p2
179 3 20480 mmcblk0p3
179 4 4096 mmcblk0p4
179 5 4096 mmcblk0p5
179 6 4096 mmcblk0p6
179 7 4096 mmcblk0p7
259 0 8192 mmcblk0p8
259 1 8192 mmcblk0p9
259 2 8192 mmcblk0p10
259 3 8192 mmcblk0p11
259 4 4096 mmcblk0p12
259 5 20480 mmcblk0p13
259 6 4096 mmcblk0p14
259 7 4096 mmcblk0p15
259 8 5120000 mmcblk0p16
259 9 12288 mmcblk0p17
259 10 4096 mmcblk0p18
259 11 774144 mmcblk0p19
259 12 5120000 mmcblk0p20
259 13 19263488 mmcblk0p21
179 24 512 mmcblk0rpmb
179 16 4096 mmcblk0boot1
179 8 4096 mmcblk0boot0

root@lt03wifi:/ # parted /dev/block/mmcblk0 print
Model: MMC MBG4GC (sd/mmc)
Disk /dev/block/mmcblk0: 31.3GB
Sector size (logical/physical): 512B/512B
Partition Table: gpt

Number Start End Size File system Name Flags
1 4194kB 8389kB 4194kB BOTA0
2 8389kB 12.6MB 4194kB BOTA1
3 12.6MB 33.6MB 21.0MB ext4 EFS
4 33.6MB 37.7MB 4194kB m9kefs1
5 37.7MB 41.9MB 4194kB m9kefs2
6 41.9MB 46.1MB 4194kB m9kefs3
7 46.1MB 50.3MB 4194kB CARRIER
8 50.3MB 58.7MB 8389kB PARAM
9 58.7MB 67.1MB 8389kB BOOT
10 67.1MB 75.5MB 8389kB RECOVERY
11 75.5MB 83.9MB 8389kB OTA
12 83.9MB 88.1MB 4194kB CDMA-RADIO
13 88.1MB 109MB 21.0MB RADIO
14 109MB 113MB 4194kB TOMBSTONES
15 113MB 117MB 4194kB TDATA
16 117MB 5360MB 5243MB ext4 HIDDEN
17 5360MB 5373MB 12.6MB PERSDATA
18 5373MB 5377MB 4194kB RESERVED2
19 5377MB 6170MB 793MB ext4 CACHE
20 6170MB 11.4GB 5243MB ext2 SYSTEM
21 11.4GB 31.1GB 19.7GB ext4 USERDATA

Any ideas what is going on? Some normal/typical numbers to confirm what I should be looking at would be a big help as well (never really looked at the partitioning when everything was fine).