have a 931.5 GibiByte SSD pair in raid1 (mdraid) as cache LV for a data LV on 1.8 TebiByte raid1 (mdraid) pair of larger spinning disk. these disks are hosted by a small 4GB big.little ARM system running4.4.192-rk3399 (armbian 5.98 bionic). parameters were set with: lvconvert --type cache --cachemode writeback --cachepolicy smq --cachesettings migration_threshold=10000000 the system lost power recently. after coming back up from the crash and resyncing the raid pair (no issues there), I get the disks online and "lvchange -ay" the dm-cache device. the system immediately starts consuming all memory over the next few seconds, system used memory is going up to 3500M (last I can see), cached is going down to 163M (last I can see), the kernel kills all processes (they are faulting in ext4_filemap_fault -> out_of_memory -> oom_kill_process) so this happens every time I reboot and try it. is 4G just not enough system memory to run a dm-cache device? it was in perfect working order before the crash and nicely optimizing my nightly rsyncs on top of the cached device. why's it going crazy when it goes online (third second in below dstat 1), resulting in crashing system? how do I get it online to remove my data from it? usr sys idl wai stl| read writ| int csw | used free buff cach 2 3 95 0 0| 0 0 | 450 594 |93.9M 413M 10.3M 3184M 0 0 100 0 0| 0 0 | 78 130 |93.4M 413M 10.3M 3184M 2 6 91 1 0|8503k 0 |2447 4554 | 111M 393M 10.3M 3187M 5 9 78 7 0| 11M 34k|7932 16k| 145M 358M 10.3M 3187M 3 25 60 12 0| 277M 6818k|5385 10k| 602M 22.1M 10.4M 3068M 9 64 21 5 0| 363M 124M|5509 9276 |1464M 39.9M 10.3M 2211M 2 31 40 27 0| 342M 208M|5487 9495 |1671M 21.8M 10.3M 2027M 1 10 63 26 0| 96M 128M|2197 4051 |1698M 23.9M 10.3M 1999M 1 15 55 29 0| 138M 225M|2361 5007 |1730M 25.3M 10.3M 1966M 3 16 54 28 0| 163M 234M|3118 5021 |1768M 23.8M 10.3M 1930M 1 8 58 33 0| 85M 128M|1541 2860 |1795M 24.3M 10.3M 1904M 2 10 53 35 0| 97M 161M|1949 3275 |1820M 24.1M 10.3M 1879M 3 16 55 26 0| 148M 235M|2927 4733 |1865M 24.1M 10.3M 1835M 1 9 65 25 0| 83M 137M|1764 3521 |1891M 23.9M 10.3M 1810M 5 59 29 6 0| 340M 97M|4291 5530 |3569M 39.5M 10.3M 163M 2 22 51 25 0| 339M 236M|5985 9526 |3500M 109M 10.3M 163M note: tried adding some swap on unrelated slow disk, which seems to delay it by some seconds, but ultimate result is always the same: OOM every process killed and reboot... here is paste from "lvs -a" just before "lvchange -ay raidbak4/bakvol4" which brings the system down: LV VG Attr LSize Pool Origin [bakcache4] raidbak4 Cwi---C--- <931.38g [bakcache4_cdata] raidbak4 Cwi------- <931.38g [bakcache4_cmeta] raidbak4 ewi------- 48.00m bakvol4 raidbak4 Cwi---C--- 1.75t [bakcache4] [bakvol4_corig] [bakvol4_corig] raidbak4 owi---C--- 1.75t [lvol0_pmspare] raidbak4 ewi------- 48.00m this lvchange then brings the system down with OOM death within 10 or so seconds. online access to the cached data seems to be impossible... _______________________________________________ linux-lvm mailing list linux-lvm@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/linux-lvm read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
