Not enough server memory when start VM

Paolo

xcp-ng 8.2
host server total memory: 64 GB
host server available memory: 25.5 GB
Already running VMs: 7
Dom0 memory: 8 GB
Dom0 top info:

KiB Mem :  8110196 total,  5590192 free,   550848 used,  1969156 buff/cache
KiB Swap:  1048572 total,  1048572 free,        0 used.  7355948 avail Mem

VM memory parameters

[11:50 host1 ~]# xe vm-param-list uuid=bc3a1a8e-1e64-fd0b-ecc8-ae8e1bd7a6e0 | grep " memory-"
                         memory-actual ( RO): 0
                         memory-target ( RO): 0
                       memory-overhead ( RO): 140509184
                     memory-static-max ( RW): 17179869184
                    memory-dynamic-max ( RW): 17179869184
                    memory-dynamic-min ( RW): 17179869184
                     memory-static-min ( RW): 1073741824

When starting this VM with 16GB RAM (fixed) using with XCP-ng Center the following error is displayed:
"not enough server memory is available to perform this operation"

When starting the same VM with XOA the error is NO_HOSTS_AVAILABLE.

I've tried to decrease the VM memory to 8 GB but the error persists.

I think there is a lot of available memory...
What i should check?

Thanks.

olivierlambert

Can you do it from command line? xe vm-start uuid=bc3a1a8e-1e64-fd0b-ecc8-ae8e1bd7a6e

Paolo

@olivierlambert Also from command line the VM cannot be started:

[17:50 host1 ~]# xe vm-start uuid=bc3a1a8e-1e64-fd0b-ecc8-ae8e1bd7a6e0
There are no suitable hosts to start this VM on.
The following table provides per-host reasons for why the VM could not be started:

host1    : Cannot start here [Not enough free memory]


There were no servers available to complete the specified operation.

Danp

Please post the output of xe host-list params=memory-free

Also post the output of xe vm-compute-maximum-memory uuid=bc3a1a8e-1e64-fd0b-ecc8-ae8e1bd7a6e0 total=`xe host-list params=memory-free --minimal`

Paolo

[11:40 host1 ~]# xe host-list params=memory-free
memory-free ( RO)    : 27513360384

[11:40 host1 ~]# xe vm-compute-maximum-memory uuid=bc3a1a8e-1e64-fd0b-ecc8-ae8e1bd7a6e0 total=`xe host-list params=memory-free --minimal`
27292336128

Thanks for your help...
& Merry Christmas to all XCP-ng community!

olivierlambert

I there any other host in the pool? Is it attached to the same SRs as all other VMs?

Paolo

Hi Olivier,

The host is a single host (no other hosts in the pool) with local storage (EXT) only.
I've done some other tests:

Tried to detach disks, re-create VM, re-attach disks: no success
the VM starts if memory is reduced from 16GB to 10GB
I've created a new VM (W2019 template) and the behaviour is the same: with 16GB memory the error is "not enought memory"; with 10GB the VM starts
Starting one of the 10GB memory VM, no other VM can be started (also with only 1 GB memory)

It's like the host has lost 15GB of free memory...

SOLVED: Restarting Toolstack the problem is solved: now i can start 16GB VM and another 9GB VM to use all available memory (25,5 GB).

I'd be curious to know what happened...

olivierlambert

Yeah that's weird. Like if XAPI was keeping wrong data on running VMs.

Intra1910

Hello,

On a new server where I migrated about 15 VMs, same problem suddenly!

Thanks for the tip, the Restarting Toolstack worked!

(XCP-NG 8.2 / XCP-ng Center 20.04.01)