Intermittent Template Download Failure (NOT_DOWNLOADED) in CloudStack 4.20.1.0 with Linstor Primary Storage

Hi all,

I’m encountering an intermittent issue when uploading templates to CloudStack 4.20.1.0 where Linstor is used as Primary Storage. Here’s the detailed breakdown:

CloudStack Version: 4.20.1.0
Primary Storage:
Linstor-controller 1.32.3-1ppa1-noble1
Linstor-satellite 1.32.3-1ppa1-noble1
DRBD_KERNEL_VERSION=9.2.14
System: Ubuntu 24.04.3 LTS
Hypervisor: KVM

When uploading a template (e.g., an Ubuntu 22.04 qcow2 image), the process intermittently fails with NOT_DOWNLOADED in Primary Storage. In my tests, 2 out of 3 upload attempts fail, while 1 succeeds randomly.

Two critical symptoms:
1. qemu-img Binary Not Found: The CloudStack agent not execute qemu-img convert (verified via strace ):
ps -ef | grep cloudstack-agent
strace -f -s 256 -p 1318808 -o /tmp/agent_trace.log

can't find execute qemu-img convert like this:
```
execve("/usr/local/sbin/qemu-img", ["qemu-img", "convert", "-n", "--target-is-zero", "-W", "-S", "1M", "-O", "raw", "-t", "none", "-U", "--image-opts", "driver=qcow2,file.filename=/mnt/.../xxx.qcow2", "/dev/drbd1105"], ...) = -1 ENOENT (No such file or directory)
```

DRBD Devices Stay “Unused”: Linstor resource listings show DRBD devices as Unused (instead of one of device InUse):

```
root@NODE76:~# linstor v l |grep 80bc7788-638e-4211-9b31-d76d037b50b3
| cs-80bc7788-638e-4211-9b31-d76d037b50b3 | NODE158 | DfltDisklessStorPool | 0 | 1105 | /dev/drbd1105 | | Unused | Diskless | Established(2) |
| cs-80bc7788-638e-4211-9b31-d76d037b50b3 | NODE76 | x86_pool_zfs_ssd | 0 | 1105 | /dev/drbd1105 | 20.00 GiB | Unused | UpToDate | Established(2) |
| cs-80bc7788-638e-4211-9b31-d76d037b50b3 | NODE83 | x86_pool_zfs_ssd | 0 | 1105 | /dev/drbd1105 | 20.00 GiB | Unused | UpToDate | Established(2) |
```

Steps to Reproduce:
1. Upload a qcow2 template (e.g., `ubuntu-22.04.4-amd64-base-UEFI.qcow2`) to CloudStack.
2. Monitor the Primary Storage (Linstor) download status.
3. Repeat the upload 3+ times and observe intermittent `NOT_DOWNLOADED` failures.

Expected Behavior:
The template should download to Primary Storage successfully every time, with `qemu-img convert` executing properly and DRBD devices showing `InUse`.

Actual Behavior:
- Intermittent failures (2 out of 3 attempts fail).
- DRBD resources remain `Unused` during failed attempts.

Questions:
- What configuration or troubleshooting steps should I take to resolve this intermittent behavior?

Any insights or guidance would be greatly appreciated!

Thanks,