I have been testing storage recently with vdbench 5.04.06. The array being tested has 112TB of usable capacity. I am using a combined data reduction ratio or 4:1 (dedup 2:1 and compression 2:1). I am attempting to precondition the array by filling it to 90% and then overwriting the LUNs. My total logical capacity is calculated as ((112.31 x 4) x .9) x 1024 = 414,020GB, and I am using 32 LUNs sized 12938GB
Phase 1 - Fill
- Fill LUNs xfersize=(128k,50,256k,50)
- Overwrite LUNs xfersize=(128k,50,256k,50)
The first fill pass runs without issue. The only problem encountered is not really a problem, however at the end of fill pass 1 DRR was reported as 5.3:1. Deduplication was as 2.6:1 and compression was reported as 2:1.
The issue - vdbench fails reporting java heap memory errors
Once the LUNs were full, any attempt to read or write from the LUNs resulted in failure. When checking the *.out file associated with the run, the errors were reported were related to java heap memory. Several attempts were made to rectify the issue, but resulted in the same outcome - failure.
Resolution
I found that by limiting the size of the LUNs, the tests would run without issue. I started by limiting the LUN size to a few hundred GB. I stepped up the size and settled on 2TB per LUN. I have not pressed further to see at what size the error would re-present itself. I had tests that I had to complete. I will do this once my current testing cycle is complete.
What I have right now is a workaround. Any suggestions as to root cause and permanent resolution would be appreciated.
The tests are running on ESXi 6.5 hosts, CentOS 7 VMs.