In this blog article we will look at the vSAN 7 U1 Compression-Only feature ,its benefits and how it fares with other space saving features on the previous releases of vSAN.
I have been asked by a lot vSAN users about vSAN only allowing us to enable Deduplication and Compression together as feature in all the releases since vSAN 6.x. Finally VMware made this announcement for vSAN compression only mode is here with vSAN 7 Update1 we can totally eliminate the additional overheads for Deduplication when using Compression-Only yet get good space savings. Let dive straight into key difference between Deduplication & Compression vs Compression-Only.
|Deduplication and Compression||Compression-Only|
|• Cache tier SSD has to perform both DD&C at the same time.For every Disk Group with DD&C we only have a single elevator (Destage thread) that constraints the rate at which we are destaging writes from cache tier||• Cache tier SSD only has to account for compression while doing De-stage and we have an elevator (Destage-thread) for every disk in the capacity tier, depending on the workload we may see almost 1.5X performance (DD&C)|
|• A capacity tier drive failure will fail the entire Disk Group, which means entire Disk Group will needs to be recreated.||• A capacity tier drive failure will not unmount the entire Disk Group, affected disk can be replaced and re-added into the Disk Group.|
|• Huge amount of resync will be triggered for a drive failure as entire Disk Group will be unmounted and the resync that is triggered will be slightly larger than the Diskgroup itself as the data is un-deduped and un-compressed. Once the data is resync to the Diskgroup, the data will be DD&C on the destination Disk group.||• Resync is triggered only for the failed drive, we reach compliant state sooner than Dd&C feature,the amount of data inflight when a capacity drive fails is far lesser than DD&C.|
Compression only feature will be very realistic for customers who wants to have a decent level of space efficiency and who cannot afford the performance impact of DD&C. Large block sequential write performance, OLTP Database VMs are expected to see better performance with compression only vs DD&C.
Compression-Only see the difference- UI
That concludes this blog article on ” vSAN 7 U1 Compression-only Feature-Walkthrough“, I will try to post a new blog specific about performance improvements with vSAN compression only and how it compares with both Dedupe and compression. If you liked this blog article feel free to share with your colleagues and friends.
Continue reading about other features on vSAN 7.0 U1 / vSAN 7 Update 1 here