When it comes to disk errors like this it is recommended to contact support for assistance. If you listed the disks by GUID and don't see it then support is the best route.
Unfortunately, this is the community edition so no support. Do you know if it is a disk I am backing up, or a disk where the backups are stored?
Agree with Chris here.. Support is your best bet. You can still get support with Community Ed.
Unfortunately, this is the community edition so no support. Do you know if it is a disk I am backing up, or a disk where the backups are stored?
Unsure as this is why support is the better bet.
Without having information about your environment it’s hard to tell but is this a physical server? In case yes you could check OOBM (like iDRAC or iLO) to see whether you see any failed disks. In case of a Windows server you also could use perfmon or other tools to identify abnormalities.
I also agree with Chris and Shane - taking this to support should be the best way to go.
Best
Lukas
Hi, running my normal weekly backup and came cross this:
7/31/2025 5:08:20 PM :: Error: Cannot process pending I/O request (offset: 453659656192, size: 65536): async reader terminated
Corrupted block processing thread failed unexpectedly
Failed to upload disk. Skipped arguments: EmulatedDiskSpec>];
Agent failed to process method {DataTransfer.SyncDisk}.
Exception from server: Cannot process pending I/O request (offset: 453659656192, size: 65536): async reader terminated
Unable to retrieve next block transmission command. Number of already processed blocks: 429608].
Failed to download disk '63d26504-899c-457e-bc3d-6e4f5ca89f35'
How can I tell which disk has the error. I listed all by disks by GUID and none matches 63d26504-899c-457e-bc3d-6e4f5ca89f35
Thank you, Henry
Hi @Hammer
Do you need more information about the type of server you are backing up, VM or physical server?
- Run Disk Health Checks on the Source VM
If you're backing up a VM, check for disk errors inside the guest OS (e.g., chkdsk on Windows).
If you're backing up a physical machine, run SMART diagnostics or vendor tools.
Disk corruption or hardware issues are a common root cause of async reader crashes.
chkdsk C: /f /r
- Check Storage Infrastructure
Validate that the source disk (VM/physical) and the backup repository storage are both healthy.
Watch for:
Latency
Read/write errors
Timeouts
Network congestion (if using networked storage like SMB, NFS, etc.)
- Review Event Logs (on Source and Veeam Proxy)
Look in Windows Event Viewer for disk, VSS, or storage-related warnings or errors.
regards
Thank you. I switched Repositories and still got the error, so concluded it was the source disk. Although interesting, Windows says there are no errors. Ended up rebuilding the PC for piece of mind.
Thank you. I switched Repositories and still got the error, so concluded it was the source disk. Although interesting, Windows says there are no errors. Ended up rebuilding the PC for piece of mind.
Glad to hear things are working. Don't forget to mark the best answer in the thread even if yours.
