vayidm

Same thing has happened in my testing. I've turned most of my disks back to XFS. Lesson learnt, don't switch without testing thoroughly first My 8TB copy finished in 12 hours and the data rate slowed to 150MB/s at the end, but like yours it stays at 200+ MB/s for a long while. When I do the ZFS copy I notice it will write at full speed for a short while, and then tank which seems to indicate some buffer has filled up or something happens to slow it down significantly.

Will give that a test. I've found it occurs from disk to disk with or without parity set up, when the disks are ZFS singles.

Ah yes I see what you mean, the memory cache? I haven't tried copying data from a share via Windows. It'll add too many variables into the mix and the main issue is really from ZFS disk to ZFS disk, with and without parity on. I haven't tried copying from share to another share yet. Most likely if the performance is that bad on the machine, it won't get better going over the network, but who knows. Either way I'm going to go back to XFS for now until i do more testing and ZFS at least performs the same when using it in a single disk pool.

No cache in front of mine (ZFS disks). I was doing the copy from /mnt/diskN to /mnt/diskN+1 using the GUI Will try a copy from XFS back to ZFS to see what the write speed is, but I'm sure it was slow. I didn't catch on to it thinking it was because of the parity drive was there, but as you have realised, the parity might slow things down, but not that slow. Either way if anyone else is experiencing the slowness at least they know what to try, to see if the speed comes back.

I've had a similar issue, although I'm getting speeds of 60-70MB/s when the disks in DiskSpeed app are capable of 250-130MB/s reads/writes (start and end of disk speeds respectively). I moved all my data onto one XFS disk, which freed up some disks to format as ZFS. I've been using ZFS single disks just purely for the dataset capabilities but when moving a share using unBalance from one ZFS disk to another, the speed is roughly 66MB/s, even with Parity disabled for speed. I've formatted one of the ZFS disks that was "slow" to read and write from as XFS, and now copying or moving from another ZFS disk to the XFS one is giving me a boost startup speed of 250MB/s and it is currently at 140MB/s having copied about 200GB already. Not sure what's going on but it seems single ZFS disks are super slow, which explains why my Parity rebuilt took almost 2-3 days going at 60-70MB/s at max. Going to switch back to XFS at least for the array and do more testing with ZFS single vdevs.

Yeah it seems it requires a big cache drive to work nicely. Will have to figure a way to keep all reads/writes on a small cache drive then use this. Thanks

Right I see, I only have a 256GB SSD cache and the domains share is too large to be on there. The appdata and system share fit on it fine. I've been searching for a plugin or a method to keep hot files on the SSD cache and for them to be written back to the array at regular intervals to try and allow me to use this plugin effectively but there currently doesn't seem to be such a thing. I guess I'll have to use the old method for now. Thanks

This is a great plugin for speeding up writes. However I've found that it always keeps my drives spinning no matter what. I think it's because there's constantly writes to my domains share (using a VM always on) which seems to keep the other disks always on due to reading the data from them as part of the reconstruct write. How do you use this plugin with a VM always running (therefore performing writes all the time).