We also have the same setup, running on affected hosts with iSCSI pool devices connected

Module                  Size  Used by
tun                    49152  0
iscsi_tcp              20480  5
libiscsi_tcp           28672  1 iscsi_tcp
libiscsi               61440  2 libiscsi_tcp,iscsi_tcp
scsi_transport_iscsi   110592  3 iscsi_tcp,libiscsi
dm_service_time        16384  4
arc4                   16384  0
md4                    16384  0
nls_utf8               16384  1
cifs                  929792  2
ccm                    20480  0
fscache               380928  1 cifs
bnx2fc                159744  0
cnic                   81920  1 bnx2fc
uio                    20480  1 cnic
fcoe                   32768  0
libfcoe                77824  2 fcoe,bnx2fc
libfc                 147456  3 fcoe,bnx2fc,libfcoe
openvswitch           147456  12
nsh                    16384  1 openvswitch
nf_nat_ipv6            16384  1 openvswitch
nf_nat_ipv4            16384  1 openvswitch
nf_conncount           16384  1 openvswitch
nf_nat                 36864  3 nf_nat_ipv6,nf_nat_ipv4,openvswitch
8021q                  40960  0
garp                   16384  1 8021q
mrp                    20480  1 8021q
stp                    16384  1 garp
llc                    16384  2 stp,garp
ipt_REJECT             16384  3
nf_reject_ipv4         16384  1 ipt_REJECT
xt_tcpudp              16384  9
xt_multiport           16384  1
xt_conntrack           16384  5
nf_conntrack          163840  6 xt_conntrack,nf_nat,nf_nat_ipv6,nf_nat_ipv4,openvswitch,nf_conncount
nf_defrag_ipv6         20480  2 nf_conntrack,openvswitch
nf_defrag_ipv4         16384  1 nf_conntrack
libcrc32c              16384  3 nf_conntrack,nf_nat,openvswitch
iptable_filter         16384  1
dm_multipath           32768  5 dm_service_time
intel_powerclamp       16384  0
crct10dif_pclmul       16384  0
crc32_pclmul           16384  0
ghash_clmulni_intel    16384  0
pcbc                   16384  0
aesni_intel           200704  0
aes_x86_64             20480  1 aesni_intel
crypto_simd            16384  1 aesni_intel
cryptd                 28672  3 crypto_simd,ghash_clmulni_intel,aesni_intel
glue_helper            16384  1 aesni_intel
dm_mod                151552  22 dm_multipath
ipmi_si                65536  0
i2c_i801               28672  0
sg                     40960  0
ipmi_devintf           20480  0
i7core_edac            28672  0
lpc_ich                28672  0
ipmi_msghandler        61440  2 ipmi_devintf,ipmi_si
i5500_temp             16384  0
acpi_power_meter       20480  0
sunrpc                413696  1
ip_tables              28672  2 iptable_filter
x_tables               45056  6 xt_conntrack,iptable_filter,xt_multiport,xt_tcpudp,ipt_REJECT,ip_tables
sr_mod                 28672  0
cdrom                  69632  1 sr_mod
sd_mod                 53248  7
ata_generic            16384  0
pata_acpi              16384  0
uhci_hcd               49152  0
lpfc                  958464  4
ata_piix               36864  0
nvmet_fc               32768  1 lpfc
nvmet                  69632  1 nvmet_fc
libata                274432  3 ata_piix,pata_acpi,ata_generic
nvme_fc                45056  1 lpfc
nvme_fabrics           24576  1 nvme_fc
ehci_pci               16384  0
igb                   233472  0
ehci_hcd               90112  1 ehci_pci
nvme_core              81920  2 nvme_fc,nvme_fabrics
ixgbe                 380928  0
megaraid_sas          167936  2
scsi_transport_fc      69632  4 fcoe,lpfc,libfc,bnx2fc
scsi_dh_rdac           16384  0
scsi_dh_hp_sw          16384  0
scsi_dh_emc            16384  0
scsi_dh_alua           20480  5
scsi_mod              253952  19 fcoe,lpfc,scsi_dh_emc,sd_mod,dm_multipath,scsi_transport_iscsi,scsi_dh_alua,scsi_transport_fc,libfc,iscsi_tcp,bnx2fc,libiscsi,megaraid_sas,libata,sg,scsi_dh_rdac,scsi_dh_hp_sw,sr_mod
ipv6                  548864  173 nf_nat_ipv6
crc_ccitt              16384  1 ipv6

@dave thx for this hint. yes we have iSCSI SR's attached

@stormi
we have 8.1
I haven't start yet the services. can the openvswitch service safely restart without any impact?
nothing changed after rsyslog restart

@stormi
i have the problem on a PoolMaster with 2 running VM's with memory alerts.
here are some infos. may you find something.

slabtop.txt
xehostparamlist.txt
xltop.txt
meminfo.txt
top.txt
grub.cfg.txt

sorry, can't add images. it seems there is something broken with some node modules.

@olivierlambert this still happens at 8.1 also
@stormi it seems that the memory is eating somewhere and doesn't point to specific program. @dave also described here https://xcp-ng.org/forum/post/31693

hi all,
i have similar behave like @mtango on xo-server 5.60.0 - xo-web 5.60.0 on a fresh installed Ubuntu 20.04 LTS.
I'm able to choose the disk and then the partition.
If i choose a boot partition with ext4, i can see all files.
If i choose a partition with lvm, i get an error, as you can see in the logfile:

Jun  9 13:59:46 xoa-server systemd[1]: Starting LVM event activation on device 7:3...
Jun  9 13:59:46 xoa-server lvm[15934]:   pvscan[15934] PV /dev/loop3 online, VG cl_server2backup is complete.
Jun  9 13:59:46 xoa-server lvm[15934]:   pvscan[15934] VG cl_server2backup run autoactivation.
Jun  9 13:59:46 xoa-server lvm[15934]:   PVID Mq7sxO-2CQu-1UJp-ovp0-PnaR-Aumk-gRzgkY read from /dev/loop3 last written to /dev/xvda2.
Jun  9 13:59:46 xoa-server lvm[15934]:   pvscan[15934] VG cl_server2backup not using quick activation.
Jun  9 13:59:46 xoa-server lvm[15934]:   2 logical volume(s) in volume group "cl_server2backup" now active
Jun  9 13:59:47 xoa-server systemd[1]: Finished LVM event activation on device 7:3.
Jun  9 13:59:47 xoa-server systemd[1]: Started /sbin/lvm pvscan --cache 7:3.
Jun  9 13:59:47 xoa-server systemd[977]: tmp-tmp\x2d12262nUuODahdRdV9.mount: Succeeded.
Jun  9 13:59:47 xoa-server systemd[1]: tmp-tmp\x2d12262nUuODahdRdV9.mount: Succeeded.
Jun  9 13:59:47 xoa-server lvm[15986]:   pvscan[15986] device 7:3 /dev/loop3 excluded by filter.
Jun  9 13:59:47 xoa-server systemd[1]: Stopping LVM event activation on device 7:3...
Jun  9 13:59:47 xoa-server systemd[1]: run-rbb9f6e183716490a87f59a7acc3a6db1.service: Succeeded.
Jun  9 13:59:47 xoa-server lvm[15989]:   pvscan[15989] device 7:3 /dev/loop3 excluded by filter.
Jun  9 13:59:47 xoa-server systemd[1]: lvm2-pvscan@7:3.service: Succeeded.
Jun  9 13:59:47 xoa-server systemd[1]: Stopped LVM event activation on device 7:3.
Jun  9 13:59:52 xoa-server systemd[1]: Starting LVM event activation on device 7:3...
Jun  9 13:59:52 xoa-server lvm[16001]:   pvscan[16001] PV /dev/loop3 online, VG cl_server2backup is complete.
Jun  9 13:59:52 xoa-server lvm[16001]:   pvscan[16001] VG cl_server2backup run autoactivation.
Jun  9 13:59:52 xoa-server lvm[16001]:   PVID Mq7sxO-2CQu-1UJp-ovp0-PnaR-Aumk-gRzgkY read from /dev/loop3 last written to /dev/xvda2.
Jun  9 13:59:52 xoa-server lvm[16001]:   pvscan[16001] VG cl_server2backup not using quick activation.
Jun  9 13:59:52 xoa-server lvm[16001]:   2 logical volume(s) in volume group "cl_server2backup" now active
Jun  9 13:59:52 xoa-server systemd[1]: Finished LVM event activation on device 7:3.
Jun  9 13:59:53 xoa-server kernel: [ 5776.274595] XFS (loop4): Mounting V5 filesystem in no-recovery mode. Filesystem will be inconsistent.
Jun  9 13:59:53 xoa-server systemd[977]: tmp-tmp\x2d12262c7TAY6NWwQG5.mount: Succeeded.
Jun  9 13:59:53 xoa-server systemd[1]: tmp-tmp\x2d12262c7TAY6NWwQG5.mount: Succeeded.
Jun  9 13:59:53 xoa-server kernel: [ 5776.295448] XFS (loop4): Unmounting Filesystem
Jun  9 13:59:53 xoa-server systemd[1]: Started /sbin/lvm pvscan --cache 7:3.
Jun  9 13:59:53 xoa-server systemd[1]: Stopping LVM event activation on device 7:3...
Jun  9 13:59:53 xoa-server lvm[16069]:   pvscan[16069] device 7:3 /dev/loop3 excluded by filter.
Jun  9 13:59:53 xoa-server lvm[16070]:   pvscan[16070] device 7:3 /dev/loop3 excluded by filter.
Jun  9 13:59:53 xoa-server systemd[1]: lvm2-pvscan@7:3.service: Succeeded.
Jun  9 13:59:53 xoa-server systemd[1]: Stopped LVM event activation on device 7:3.
Jun  9 13:59:53 xoa-server systemd[1]: run-r4d20647bef3942d2a439dcf7d9b50d9b.service: Succeeded.
Jun  9 13:59:53 xoa-server systemd[1]: tmp-tmp\x2d12262bv6erTqqwfL9.mount: Succeeded.
Jun  9 13:59:53 xoa-server systemd[977]: tmp-tmp\x2d12262bv6erTqqwfL9.mount: Succeeded.
Jun  9 13:59:53 xoa-server xo-server[12262]: 2020-06-09T13:59:53.545Z xo:api WARN admin@admin.net | backupNg.listFiles(...) [879ms] =!> TypeError [ERR_INVALID_ARG_TYPE]: The "path" argument must be of type string. Received undefined

Any ideas ??

THX2all