Permabit VDO on a Linux Laptop – Great Performance and 5:1 Space Savings
I get asked about VDO performance all the time and I’ve written several posts about big systems where we’ve seen spectacular performance numbers including 8 GB/s throughput and 650,000 mixed random 4 KB IOPS. But what about performance on smaller systems for developers? How about a laptop?
A couple weeks ago I installed VDO version 6 on my Lenovo X230 laptop running Red Hat Enterprise Linux 7.3 and here’s a summary of what I saw. The Lenovo X230 is an older model dating back from 2012 and the days of Intel’s i5-3230 (Ivy Bridge) dual-core processor. It’s equipped with a Crucial Technologies M500 240 GB drive also from the same era.
As I’ve often written about in the past, deduplication and compression have costs associated with them. To measure IOPS, Permabit uses the open-source Flexible IO Tester (fio) utility to measure performance of random and sequential workloads. Since VDO operates on 4 KB blocks, our testing focuses on performance at the 4 KB granularity. I found an increase in random write performance of approximately 20% (from 38,000 up to 46,000 4 KB IOPS) by adding VDO, while random reads had virtually no impact on performance. The increase in write performance comes about because VDO makes writes sequential, which is generally a faster operation on laptop SSDs.
To test throughput, I used larger 1 MB block sizes at a queue depth of 1. This is where I’d expect the performance of primary deduplication to have the most overhead because consumer flash drives are heavily optimized to benefit larger I/O operations. To my surprise, I saw a respectable average throughput of 160 MB/s with VDO (versus 180 MB/s without) and an even more respectable 500 MB/s with VDO (versus 460 MB/s without) on sequential reads. In this second case, VDO was performing better than baseline because VDO compresses the fio output, which requires fewer IOs to read it back in.
Now that I’m using VDO on my laptop, I frankly can’t even tell it is there. Its sitting below my /home file system which contains a number of applications including a large number of VMs I use for testing purposes with GNOME Boxes. The space savings on my /home file system currently at 81%.
Overall, this looks like a great use case. I could get away with a $50 128 GB SSD instead of a $100 240 GB model or, better yet, I could put off the performance tax that I’ve seen with these consumer-grade drives as they approach full capacity!
To find out more about this and many other great use cases for Permabit VDO data reduction for Linux, visit us next week at Red Hat Summit in the Storage Partner Showcase booth #206.