I built a small 4-node all-flash VSAN for a specific use at my company. We didn’t need high performance, but we wanted the space efficiencies of dedupe/compression plus erasure encoding (in our R5).
Note that FTT=1, I could have tested FTT=2 for R1 but not for R5 so I didn’t bother.
4xDL380 Gen9 servers with 512 GB RAM connected via 10GB running ESXi 6.0u2 Patch 4
2xDiskgroups of 800gb cache SSD and 2×3.2TB SSD capacity
Overall, 40+ TB available prior to FTT and efficiencies
8 VMs 70 read, 100% rand, threads, 10 disks of 28GB, no warmup, ran for one hour. Most tests only 7/8 vms finished
*These tests had 8VMs finish, multiplied by 7/8 to scale the results
|Compression/Dedupe||No Compression/No Dedupe|
|R5 w/compress||R1 w/compress||R5||R1||R1 Hybrid|
My testing was a bit backwards, I started with R5 and compression and worked my way backwards. I should have started with R1 and no compression first and then layered on the other settings. Also, I had to turn compression/deduplication off which
From my testing, R1 with no compression/no dedupe was the fastest with 97721 IOPS, but I wasn’t looking for pure speed. I wanted to know what the performance penalty would be as we tried to save space. Looking at R1 compressed vs R1 non-compressed, R1 compressed is 58.91% of the IOPS of non-compressed, but compression can yield from 1.5x and up space savings
Comparing R5 and R1 uncompressed, 34764 vs 97721 IOPS or 33.58% of the R1 uncompressed. Savings would be around 1.33x (ratio is around 75%)
R5 compressed vs R5 was weird, it was almost the exactly the same though IOPs. Savings would be maybe 1.5x conservatively (ratio is around 67%)
R5 compressed vs R1 compressed was 60.39% of IOPS. Savings would be 1.33x convervatively (ratio is around 75%)
R5 compressed vs R1 was 35.57% which is the biggest difference, but the space used ratio is around 50%
R1 compressed vs R5 uncompressed is 165.58%, space used is ratio is about 88%
So what should you go with? Of course it depends.
Max storage: R5 with compression
Max performance: R1 no compression
Best mix of storage savings and performance: R1 with compression
Thank you for sharing those results.
I was just doing similar test on VSAN 6.5 with R5 with dedup / compression enabled on Dell’s R630’s and the results were similar in terms of throughput (130-140 MB/s).
The question is why those numbers are so low. Any ideas?
No idea, but Chei (one of the authors of hcibench) pointed out that I didn’t run disk prep or clear cache. I’m going to re-run everything again. I’m not hopeful on the R5 results though, I’m guessing the erasure coding calculation plus the dedup lookup have a much larger penalty. If I remember I’m going to look at the performance charts for the back end to see how busy it is during the runs
Thank you, Chris.
Let me know how it goes with the testing.
Hi Roman, please see my updated post http://blog.chrischua.net/2017/03/27/updated-comparing-performance-r5-vs-r1-with-and-without-compressiondedupe-on-all-flash-vsan/
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Thank you Chris! Great addition to the test results.
I am going to implement those changes after confirming them with VMware and et you know about how performance improves as a result of those adjustments.
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