I've been dabbling with OpenZFS for a little while but there are a few nagging things that have kept me from wholesale adopting it. I will admit up front that I haven't tried as hard as I probably could to figure these things out. Hopefully there are some obvious things that someone can just quickly point out.
My main issue is that it seems very slow in several situations:
1. Large Pool To Pool Copies: Since I've never fully settled on a solution for my data, I've ended up copying it around quite a bit, from pool to pool. What I have noticed is that this process (pool to pool copy) gets very slow very quickly. It starts off OK but quickly becomes horribly slow. These are typically large pools. For example, a mirrored pair of 6TB drives copying to another similar pool. Zevo never seemed nearly that slow. HFS is not anywhere near that slow. Also, it seems that the entire memory of the computer, no matter how large, is quickly consumed. There have been discussions in the past about using a Terminal command to limit the use of memory as cache but the last I looked there wasn't a good way to make it persistent, nor do I know if this is truly the answer to my issue.
2. Folders Take Long To Display Contents: This seems true even with smaller pools. For example, while on a long vacation recently, I brought along two 2TB USB3 drives and ran them as a mirror. For each camera with me, I made a folder in the root of the pool to hold photos and videos from that device. After mounting the pool, when I click on a folder that has any decent amount of content, it takes a long time before the list of files is displayed in the Finder. For example, I just clicked a folder that contains 270GB in 6,300 items. It took over TWO MINUTES before Finder showed me the contents of the folder. This is a fairly simple config of a top-config 2015 15" MacBook Pro (16GB mem) with the pool consisting of just the two 2TB USB3 drives. No other pools mounted. Is this normal behavior? Makes it a real pain to use. It is definitely tied to the size of the folder clicked. Smaller folders show their contents much more quickly, although still much more slowly than HFS. One final thing: once the contents of the folder have been displayed, clicking that folder again results in nearly instantaneous display of contents. It's just the first click after import that's horrible.
3. Here's another issue that just happened (but has happened many times in the past). I'm copying a card full of pics and videos to a zpool. In this case it's the same pool described in number 2 above. It gets to the end of the copy and never finishes. I have to end up killing Finder. In the current case, it was copying about 128GB of data from a card to the pool. It has been stuck on finishing in "About 5 seconds" for about 15 minutes or more. It says "Copying 0 items" and lists the amount copied so far as "127.80 GB of 127.8 GB" so it gives the appearance of being done. At the same time, the fans on my computer are running very fast (audible, which they almost never are on my MBP). As soon as I relaunch Finder, the fans begin to slow down. I check my pictures, and the final one, which it was supposedly working on at the end, is copied just fine. So I'm not sure what it thinks it hasn't done yet.
I know I'm short on details here so please just ask. And sorry if the solutions to these issues are super obvious. Thanks for any help.