Backup disk full but urbackup reports way less usage

1

I have a 4TB backup drive connected to urbackup.

image
image825×268 4.91 KB

/dev/sda1 3.7T 3.6T 4.1M 100% /mnt/backupserver

The 4TB disk is completely full but urbackup only knows about 2TB for some reason. Remove unknown doesn’t seem to help either.
urbackup-remove-unknown-2026-04-26.log.gz (5.3 MB)

Any ideas?

Ncdu reports no usage (as expected due to btrfs)

ncdu 1.19 ~ Use the arrow keys to navigate, press ? for help                                                                                                                                             
--- /mnt/backupserver/urbackup --------------------------------------------------------------------------------------------------------------------------------------------------------------------------
.   8.0 KiB [############################] /backups                                                                                                                                                      
    4.0 KiB [##############              ]  docker-compose.yml                                                                                                                                           

sudo btrfs filesystem usage /mnt/backupserver 
Overall:
    Device size:                   3.64TiB
    Device allocated:              3.64TiB
    Device unallocated:            1.04MiB
    Device missing:                  0.00B
    Device slack:                  3.00KiB
    Used:                          3.55TiB
    Free (estimated):              3.82MiB      (min: 3.82MiB)
    Free (statfs, df):             3.82MiB
    Data ratio:                       1.00
    Metadata ratio:                   2.00
    Global reserve:              512.00MiB      (used: 32.00KiB)
    Multiple profiles:                  no

Data,single: Size:3.43TiB, Used:3.43TiB (100.00%)
   /dev/sda1       3.43TiB

Metadata,DUP: Size:106.00GiB, Used:60.36GiB (56.94%)
   /dev/sda1     212.00GiB

System,DUP: Size:32.00MiB, Used:400.00KiB (1.22%)
   /dev/sda1      64.00MiB

Unallocated:
   /dev/sda1       1.04MiB

Snapshots also seem to match with the backup count (101 vs. 99 / 2 Clients):

ID 262 gen 3116 top level 5 path urbackup/backups/home-services/250501-2325
ID 269 gen 11532 top level 5 path urbackup/backups/Felix-PC/250503-2227
ID 626 gen 46295 top level 5 path urbackup/backups/Felix-PC/250907-1432
ID 775 gen 53199 top level 5 path urbackup/backups/Felix-PC/251001-1218
ID 887 gen 60396 top level 5 path urbackup/backups/home-services/251020-0843
ID 924 gen 66620 top level 5 path urbackup/backups/home-services/251105-1911
ID 940 gen 81919 top level 5 path urbackup/backups/Felix-PC/251107-2320
ID 960 gen 67716 top level 5 path urbackup/backups/home-services/251112-0232
ID 961 gen 67721 top level 5 path urbackup/backups/home-services/251112-0732
ID 962 gen 79025 top level 5 path urbackup/backups/home-services/251112-1233
ID 1026 gen 80600 top level 5 path urbackup/backups/home-services/251203-1453
ID 1046 gen 81509 top level 5 path urbackup/backups/home-services/251207-1443
ID 1050 gen 81543 top level 5 path urbackup/backups/home-services/251207-1947
ID 1051 gen 81565 top level 5 path urbackup/backups/home-services/251208-0050
ID 1052 gen 81578 top level 5 path urbackup/backups/home-services/251208-0556
ID 1053 gen 81599 top level 5 path urbackup/backups/home-services/251208-1057
ID 1054 gen 81604 top level 5 path urbackup/backups/home-services/251209-0245
ID 1055 gen 81612 top level 5 path urbackup/backups/home-services/251209-0846
ID 1056 gen 81772 top level 5 path urbackup/backups/home-services/251209-1348
ID 1057 gen 92575 top level 5 path urbackup/backups/home-services/251209-1851
ID 1071 gen 83822 top level 5 path urbackup/backups/Felix-PC/251215-1137
ID 1098 gen 85902 top level 5 path urbackup/backups/Felix-PC/260101-1940
ID 1151 gen 90319 top level 5 path urbackup/backups/Felix-PC/260127-2135
ID 1170 gen 93213 top level 5 path urbackup/backups/home-services/260212-1915
ID 1209 gen 94268 top level 5 path urbackup/backups/home-services/260219-1811
ID 1251 gen 95653 top level 5 path urbackup/backups/Felix-PC/260225-1825
ID 1257 gen 95724 top level 5 path urbackup/backups/home-services/260226-1657
ID 1297 gen 96934 top level 5 path urbackup/backups/Felix-PC/260304-1923
ID 1304 gen 97185 top level 5 path urbackup/backups/home-services/260305-2008
ID 1328 gen 98853 top level 5 path urbackup/backups/Felix-PC/260309-2051
ID 1337 gen 98880 top level 5 path urbackup/backups/home-services/260312-1722
ID 1365 gen 99789 top level 5 path urbackup/backups/Felix-PC/260316-1548
ID 1367 gen 99886 top level 5 path urbackup/backups/Felix-PC/260316-2100
ID 1372 gen 99934 top level 5 path urbackup/backups/Felix-PC/260317-1320
ID 1374 gen 100042 top level 5 path urbackup/backups/Felix-PC/260317-1835
ID 1378 gen 100112 top level 5 path urbackup/backups/Felix-PC/260318-1231
ID 1382 gen 100275 top level 5 path urbackup/backups/Felix-PC/260318-2244
ID 1387 gen 100316 top level 5 path urbackup/backups/home-services/260319-2048
ID 1388 gen 100423 top level 5 path urbackup/backups/Felix-PC/260319-2108
ID 1399 gen 100896 top level 5 path urbackup/backups/Felix-PC/260321-1349
ID 1401 gen 100917 top level 5 path urbackup/backups/Felix-PC/260321-1858
ID 1403 gen 101005 top level 5 path urbackup/backups/Felix-PC/260322-0009
ID 1407 gen 101071 top level 5 path urbackup/backups/Felix-PC/260322-1556
ID 1409 gen 101195 top level 5 path urbackup/backups/Felix-PC/260322-2109
ID 1415 gen 101288 top level 5 path urbackup/backups/Felix-PC/260323-1814
ID 1417 gen 108377 top level 5 path urbackup/backups/Felix-PC/260324-0017
ID 1424 gen 110770 top level 5 path urbackup/backups/home-services/260326-1900
ID 2115 gen 111634 top level 5 path urbackup/backups/Felix-PC/260401-1502
ID 2117 gen 111740 top level 5 path urbackup/backups/Felix-PC/260401-2014
ID 2122 gen 112064 top level 5 path urbackup/backups/Felix-PC/260402-1653
ID 2123 gen 112090 top level 5 path urbackup/backups/home-services/260402-2059
ID 2147 gen 112893 top level 5 path urbackup/backups/Felix-PC/260407-1050
ID 2150 gen 112920 top level 5 path urbackup/backups/Felix-PC/260407-1601
ID 2152 gen 113061 top level 5 path urbackup/backups/Felix-PC/260407-2113
ID 2156 gen 113101 top level 5 path urbackup/backups/Felix-PC/260408-1255
ID 2158 gen 113149 top level 5 path urbackup/backups/Felix-PC/260408-1948
ID 2161 gen 113327 top level 5 path urbackup/backups/Felix-PC/260409-0439
ID 2163 gen 113350 top level 5 path urbackup/backups/Felix-PC/260409-0949
ID 2165 gen 113597 top level 5 path urbackup/backups/Felix-PC/260409-1454
ID 2167 gen 113384 top level 5 path urbackup/backups/home-services/260409-2318
ID 2187 gen 114417 top level 5 path urbackup/backups/Felix-PC/260413-1537
ID 2189 gen 114530 top level 5 path urbackup/backups/Felix-PC/260413-2049
ID 2194 gen 114588 top level 5 path urbackup/backups/Felix-PC/260414-1434
ID 2196 gen 114755 top level 5 path urbackup/backups/Felix-PC/260414-2208
ID 2206 gen 115204 top level 5 path urbackup/backups/Felix-PC/260416-1414
ID 2208 gen 115243 top level 5 path urbackup/backups/Felix-PC/260416-1929
ID 2209 gen 115257 top level 5 path urbackup/backups/home-services/260416-2051
ID 2210 gen 115396 top level 5 path urbackup/backups/Felix-PC/260417-0042
ID 2211 gen 115369 top level 5 path urbackup/backups/home-services/260417-0153
ID 2212 gen 115379 top level 5 path urbackup/backups/home-services/260417-0656
ID 2213 gen 115384 top level 5 path urbackup/backups/home-services/260417-1156
ID 2214 gen 115389 top level 5 path urbackup/backups/home-services/260417-1657
ID 2215 gen 115530 top level 5 path urbackup/backups/home-services/260417-2157
ID 2217 gen 115631 top level 5 path urbackup/backups/home-services/260418-0257
ID 2218 gen 115636 top level 5 path urbackup/backups/home-services/260418-0757
ID 2219 gen 115641 top level 5 path urbackup/backups/home-services/260418-1258
ID 2220 gen 115646 top level 5 path urbackup/backups/home-services/260418-1758
ID 2221 gen 115652 top level 5 path urbackup/backups/home-services/260418-2258
ID 2222 gen 115780 top level 5 path urbackup/backups/home-services/260419-0358
ID 2223 gen 115785 top level 5 path urbackup/backups/home-services/260419-0859
ID 2224 gen 115990 top level 5 path urbackup/backups/home-services/260419-1359
ID 2226 gen 116101 top level 5 path urbackup/backups/home-services/260419-1859
ID 2227 gen 116185 top level 5 path urbackup/backups/home-services/260420-0001
ID 2229 gen 116410 top level 5 path urbackup/backups/home-services/260420-0502
ID 2230 gen 116455 top level 5 path urbackup/backups/home-services/260420-1004
ID 2231 gen 116692 top level 5 path urbackup/backups/Felix-PC/260420-1328
ID 2232 gen 116709 top level 5 path urbackup/backups/home-services/260420-1504
ID 2233 gen 117441 top level 5 path urbackup/backups/Felix-PC/260420-1851
ID 2234 gen 116727 top level 5 path urbackup/backups/home-services/260420-2004
ID 2235 gen 116764 top level 5 path urbackup/backups/home-services/260421-0105
ID 2236 gen 117151 top level 5 path urbackup/backups/home-services/260421-0606
ID 2237 gen 117210 top level 5 path urbackup/backups/home-services/260421-1106
ID 2238 gen 117437 top level 5 path urbackup/backups/Felix-PC/260421-1447
ID 2239 gen 117428 top level 5 path urbackup/backups/home-services/260421-1607
ID 2240 gen 117450 top level 5 path urbackup/backups/home-services/260421-2110
ID 2242 gen 117485 top level 5 path urbackup/backups/home-services/260422-0214
ID 2243 gen 117490 top level 5 path urbackup/backups/home-services/260422-0715
ID 2244 gen 117495 top level 5 path urbackup/backups/home-services/260422-1216
ID 2245 gen 117500 top level 5 path urbackup/backups/home-services/260422-1716
ID 2246 gen 117506 top level 5 path urbackup/backups/home-services/260422-2217
ID 2247 gen 117510 top level 5 path urbackup/backups/home-services/260423-0317

vs.

| |Backup time|Backup ID|Incremental|Size|Archived?|Actions|
|---|---|---|---|---|---|---|
| |04/20/26 19:00|1251|Yes|3.65 GB|☑||
| |04/20/26 13:38|1249|Yes|39.33 GB|☐||
| |04/17/26 00:56|1228|Yes|2.45 GB|☐||
| |04/16/26 19:38|1226|Yes|5.45 GB|☑||
| |04/16/26 14:28|1224|Yes|44.41 GB|☐||
| |04/14/26 22:10|1214|Yes|4.67 GB|☐||
| |04/14/26 14:43|1212|Yes|6.65 GB|☐||
| |04/13/26 20:58|1207|Yes|2.74 GB|☐||
| |04/13/26 15:46|1205|Yes|37.24 GB|☐||
| |04/09/26 14:55|1183|Yes|1.48 GB|☑||
| |04/09/26 09:50|1181|Yes|1.48 GB|☐||
| |04/09/26 04:48|1179|Yes|25.75 GB|☐||
| |04/08/26 19:57|1176|Yes|2.31 GB|☐||
| |04/08/26 13:04|1174|Yes|4.29 GB|☐||
| |04/07/26 21:21|1170|Yes|1.28 GB|☐||
| |04/07/26 16:10|1167|Yes|1.87 GB|☐||
| |04/07/26 11:00|1165|Yes|36.89 GB|☐||
| |04/02/26 17:02|1140|Yes|53.2 GB|☑||
| |04/01/26 20:23|1135|Yes|5.12 GB|☐||
| |04/01/26 15:12|1133|Yes|37.21 GB|☐||
| |03/24/26 00:27|1109|Yes|8.27 GB|☑||
| |03/23/26 18:23|1107|Yes|13.01 GB|☐||
| |03/22/26 21:21|1101|Yes|21.17 GB|☐||
| |03/22/26 16:05|1099|Yes|7.96 GB|☐||
| |03/22/26 00:18|1095|Yes|15.38 GB|☐||
| |03/21/26 19:07|1093|Yes|6.9 GB|☐||
| |03/21/26 13:58|1091|Yes|25.09 GB|☐||
| |03/19/26 21:17|1080|Yes|9.44 GB|☐||
| |03/18/26 22:46|1074|Yes|9.74 GB|☑||
| |03/18/26 12:40|1070|Yes|15.67 GB|☐||
| |03/17/26 18:44|1066|Yes|2.42 GB|☐||
| |03/17/26 13:31|1063|Yes|10.4 GB|☐||
| |03/16/26 21:09|1059|Yes|2.67 GB|☐||
| |03/09/26 21:02|1020|Yes|56.28 GB|☑||
| |03/04/26 19:32|989|Yes|4.59 GB|☑||
| |02/25/26 18:34|945|Yes|825.59 MB|☑||
| |01/27/26 21:45|847|Yes|5.72 GB|☑||
| |01/01/26 19:48|796|Yes|20.93 GB|☑||
| |12/15/25 11:46|771|Yes|15.12 GB|☑||
| |11/07/25 23:32|675|Yes|1.86 GB|☑||
| |10/01/25 13:26|520|Yes|12.74 GB|☑||
| |09/07/25 14:58|372|Yes|75.19 GB|☑||
| |05/03/25 23:41|8|No|937.9 GB|☑||
| |Backup time|Backup ID|Incremental|Size|Archived?|Actions|
| |04/23/26 03:17|1264|Yes|0 bytes|☑||
| |04/22/26 22:17|1263|Yes|0 bytes|☐||
| |04/22/26 17:16|1262|Yes|0 bytes|☐||
| |04/22/26 12:16|1261|Yes|0 bytes|☐||
| |04/22/26 07:15|1260|Yes|0 bytes|☐||
| |04/22/26 02:14|1259|Yes|0 bytes|☐||
| |04/21/26 21:10|1258|Yes|0 bytes|☐||
| |04/21/26 16:07|1257|Yes|0 bytes|☐||
| |04/21/26 11:06|1255|Yes|0 bytes|☐||
| |04/21/26 06:06|1254|Yes|0 bytes|☐||
| |04/21/26 01:05|1253|Yes|0 bytes|☐||
| |04/20/26 20:04|1252|Yes|79.13 KB|☐||
| |04/20/26 15:04|1250|Yes|0 bytes|☐||
| |04/20/26 10:04|1248|Yes|0 bytes|☐||
| |04/20/26 05:02|1247|Yes|0 bytes|☐||
| |04/20/26 00:01|1245|Yes|0 bytes|☐||
| |04/19/26 18:59|1244|Yes|0 bytes|☐||
| |04/19/26 13:59|1242|Yes|0 bytes|☐||
| |04/19/26 08:59|1241|Yes|0 bytes|☐||
| |04/19/26 03:58|1240|Yes|0 bytes|☐||
| |04/18/26 22:58|1239|Yes|0 bytes|☐||
| |04/18/26 17:58|1238|Yes|0 bytes|☐||
| |04/18/26 12:58|1237|Yes|0 bytes|☐||
| |04/18/26 07:57|1236|Yes|0 bytes|☐||
| |04/18/26 02:57|1235|Yes|0 bytes|☐||
| |04/17/26 21:57|1233|Yes|0 bytes|☐||
| |04/17/26 16:57|1232|Yes|0 bytes|☐||
| |04/17/26 11:56|1231|Yes|0 bytes|☐||
| |04/17/26 06:56|1230|Yes|0 bytes|☐||
| |04/17/26 01:53|1229|Yes|0 bytes|☐||
| |04/16/26 20:51|1227|Yes|0 bytes|☑||
| |04/09/26 23:18|1185|Yes|0 bytes|☑||
| |04/02/26 20:59|1141|Yes|0 bytes|☑||
| |03/26/26 19:00|1116|Yes|67.02 KB|☑||
| |03/19/26 20:48|1079|Yes|0 bytes|☑||
| |03/12/26 17:22|1029|Yes|0 bytes|☑||
| |03/05/26 20:08|996|Yes|0 bytes|☑||
| |02/26/26 16:57|950|Yes|0 bytes|☑||
| |02/19/26 18:11|903|Yes|33.21 KB|☑||
| |02/12/26 19:15|866|Yes|1.75 MB|☑||
| |12/09/25 18:51|761|Yes|0 bytes|☑||
| |12/09/25 13:48|760|Yes|0 bytes|☑||
| |12/09/25 08:46|759|Yes|0 bytes|☑||
| |12/09/25 02:45|758|Yes|608.61 KB|☑||
| |12/08/25 10:57|757|Yes|505.7 KB|☑||
| |12/08/25 05:56|756|Yes|0 bytes|☑||
| |12/08/25 00:53|755|Yes|668 bytes|☑||
| |12/07/25 19:47|754|Yes|7.57 MB|☑||
| |12/07/25 14:43|751|Yes|3.92 MB|☑||
| |12/03/25 14:53|732|Yes|25.98 MB|☑||
| |11/12/25 12:33|697|Yes|0 bytes|☑||
| |11/12/25 07:32|696|Yes|0 bytes|☑||
| |11/12/25 02:32|695|Yes|0 bytes|☑||
| |11/05/25 19:11|659|Yes|0 bytes|☑||
| |10/20/25 08:43|631|Yes|0 bytes|☑||
| |05/01/25 23:48|1|No|101.76 GB|☐||

Any ideas where those extra 2TB are coming from?

2

I did some digging using btdu. It seems like the filebackup sizes from the UI seem to drift/become outdated when you delete backups.

btdu reports the (approximately) correct sizes:

~1.008 TiB [##########?] /250503-2227              
~363.3 GiB [###?       ] /250907-1432
~213.2 GiB [##         ] /251001-1218
~195.2 GiB [##         ] /251107-2320
~233.1 GiB [##?        ] /251215-1137
~74.00 GiB [#          ] /260101-1940
~173.5 GiB [#?         ] /260127-2135
~166.2 GiB [#?         ] /260225-1825
~36.02 GiB [?          ] /260304-1923
~84.85 GiB [#          ] /260309-2051
~39.64 GiB [?          ] /260318-2244
~52.30 GiB [?          ] /260324-0017
~122.8 GiB [#?         ] /260402-1653
~37.83 GiB [?          ] /260407-1050
~25.17 GiB [           ] /260409-0439
~57.72 GiB [?          ] /260413-1537
~10.71 GiB [           ] /260414-2208
~19.75 GiB [           ] /260416-1414
~5.282 GiB [           ] /260416-1929
~7.090 GiB [           ] /260417-0042
~81.23 GiB [#          ] /260420-1328
~5.282 GiB [           ] /260421-1447
                        [and about 2 more items]

While urbackup is way off for older backups.

image
image704×1188 15.4 KB

Any ideas how I could resolve this? Thanks to this info it just seems like, I retain too much/my disk is too small and its not an issue of files that were lost by urbackup (just the size for them is wrong).

3

This is a cool tool! Thanks for mentioning it.

The underlying problem is that this kind of calculation is really hard. The tool adds the same piece of data to multiple backups perhaps? At least you need to know somehow that if you delete something you don’t get free space since the data is referenced by multiple backups.

So the calculation UrBackup does is more of an estimation and wrong. Improving it would be difficult and would perhaps have too much of a performance cost.