First impression of Primo 0.9.8

[Bjameson]

Installed Primo 0.9.8 yesterday. The functionality inherited from 0.9.2 still works fine. However, the new Read (SSD Cache Only) needs more work.

I tested SSD Cache Only by starting/stopping a VM (.VDI, uncompressed) run in Virtualbox. Primo is slow to cache reads. It needs several restarts (of the VM, not of the host) to notice any speed improvement. The Cache Hit Rate stays below 3-4 %. Writes aren't written to the cache, only a small percentage of reads are.
The SSD cache size is 30 GB, the VM itself is 5 GB. The VM runs much slower with, than without the cache. Rebooting the host makes Primo zero out the SSD cache altogether. As far as I can see, this way of caching is counter-productive.

In my humble opinion the SSD cache should act as a dumb buffer, storing every read and write. This would dramatically increase the cache hit rate because all past data would be available instantly. Yes it wears out the SSD faster but I prefer speed over SSD life. Also the SSD cache should survive host reboots. This works for the hybrid options, so why not for this one.

Repeated the same with a hybrid 8 GB RAM L1 and 30 GB L2. Also with 64 MB L1 and 30 GB L2. This works fine, as it did in 0.9.2. The cache hit rate climbs with every VM reboot, up to 96% or more. Mostly because of the RAM cache, but using the smallest RAM size (64 MB) proved that the SSD is indeed caching. The VM starts blazingly fast, it's working very well indeed. Even after a VM and Host reboot the VM starts up instantly.

Also, if you delete a cache, the Cache Task remains. I cannot add to the orphan task and Primo creates a new task anyway. I can delete the orphan task but when I tried to create a new one, the GUI was killed by Windows 8.1 X64. This happened only once. I could not recreate the error condition, nor do I remember exactly which steps I took before it crashed. The best way to delete a cache is to delete the task, which automatically deletes the cache as well. It should work the other way around too. Delete a cache should automatically delete the cache task too. Confusing.

Primocache is a superior product but the new options need some tweaking. Overall positive, so I hope this helps a little. Keep up the good work!

[Support]

Regarding the L2 cache algorithm since version 0.9.8, please see
viewtopic.php?f=33&t=2411

if you delete a cache, the Cache Task remains. I cannot add to the orphan task and Primo creates a new task anyway. I can delete the orphan task but when I tried to create a new one, the GUI was killed by Windows 8.1 X64.

Some bugs are fixed in version 0.9.9. You can delete a volume from a cache task, or you can delete the whole cache task. You can also add volumes to existing cache tasks.