DISKSPD benchmarks disk I/O performance through the command line. It simulates different I/O patterns, measures latency, and assesses storage subsystem performance. By customizing parameters like block size, I/O depth, and threads, you can create synthetic workloads that mimic real-world scenarios and help identify potential bottlenecks. In this artcile, we shall discuss “Veeam Backup and Replication Disk I/O with diskspd”. Please, see Fixing AIX Veeam agent job startup delay issue, and Set up Veeam Backup for Microsoft Azure.
Recently, I ran into an issue where AIX backup jobs were taking longer than expected to start. After digging around, I came across a very useful Veeam KB article (KB2014) that suggests testing disk I/O to identify potential bottlenecks, especially useful when backing up to tape or dealing with performance inconsistencies.
I decided to try out one of popular tools for benchmarking and simulating disk workloads: DiskSpd (for Windows).
Step 1 – Install Disk Benchmark Tool
Make sure you have the following installed:
- diskspd– Microsoft’s free disk performance tool for Windows.
Step 2 – Run DiskSpd on Windows
Here’s the command I used:
diskspd.exe -c25G -b512K -w100 -Sh -d600 D:\testfile.dat
Explanation of parameters:
- -c25G → Size of the test file (25 GB). This should reflect the typical size of your restore points.
- -b512k → Block size of I/O operations.
- -w100 → 100% write test (you can adjust for read/write mix if needed).
- -Sh → Disables hardware and software caching for accurate results.
- -d600 → Test duration (600 seconds = 10 minutes).
Note: Using a test file that’s too small can result in artificially fast results due to caching.
And here’s what I got back from the test:
Summary:
- Total Data Written: ~384.7 GB
- Write Throughput: 656.57 MiB/s (~688 MB/s)
- IOPS: 1313.13
- No read operations, as expected with -w100
This is a very solid performance result. Sustaining over 650 MiB/s in sequential write means the disk subsystem is not a bottleneck in my scenario with AIX.
Also, you can run the same test at the AIX side, but using fio tool.
Please, see Upgrade VBR to 12.3.1: Setup detected inconsistent configuration, how to In-place upgrade of Windows Server 2022 to 2025 and how to Export and Convert Private Keys to .PEM Format in Windows.
Takeaways
- Always benchmark your backup repository if you’re experiencing slow tape performance or synthetic operations.
- Check disk health, defragmentation, caching, and filesystem-level issues.
- The
diskspdtool is lightweight and can be easily included in your troubleshooting process. - This test complements what Veeam does behind the scenes with synthetic I/O.
I hope you found this article very useful on “Veeam Backup and Replication Disk I/O with diskspd”. Please, feel free to leave a comment below.
