Hello! I just wanted to share a quick video idea; With DSM 7.0, SSD Cache BTRFS metadata pinning was added. I was wondering a few things: - What is the performance impact (compared to it being disabled - aka "regular old cache") - this might require testing of certain specific workloads* - How does this scale as you add more storage? (i.e. I'm planning to upgrade to a bigger NAS next year with more storage, should I buy NVME SSDs now at ~1Tb (recommanded cache size for my 4x12Tb SHR1 RAID) or should I wait or get a larger 2Tb drive? Maybe with your contacts at synology you might be able to figure out what is the ration between cache size and volume size for BTRFS metadata pinning I hope this is a good idea and can help, Stefano *I'm thinking about their support article: https://www.synology.com/en-global/knowledgebase/DSM/tutorial/Storage/Pin_all_Btrfs_metadata_to_SSD_cache
The new pinning option is certainly improving the performance. By default, it is disabled because it requires more SSD storage space than regular caching. When enabled it will cache mass deletions of old data, operations in Active Backup, Hyper Backup, and snapshots.
Improvements will be seen on IOPS tests. If you gave 1GbE network, data transfer speeds will remain the same.
If you want to add more cache the best way to figure out capacity is to use the cache advisor app. This will calculate an estimated number.
More cache will also mean more RAM required.
I hope this helps.