I'm a bit confused on ZFS sync when it comes to PLP arrays.
I'm setting up a bunch of HGST S840 2TB SAS drives and have been playing around with 6x in a RAID-Z1 to create a 11TB NFS SAN Backend for my ESXi hosts over 4x10Gbe.
With sync=always I get approximately 100MB/sec write speeds on the array. With Sync=disabled I get approximately 200MB/sec.
These numbers seem off, considering I get pretty similar results on a single drive, but I'm going to pull things apart tomorrow and make sure its not performance issues due to PCIe passthrough or other things.
The question I have is, since these disks have PLP in the form of massive capacitors. Do I need to have sync=always, or is sync=disabled fine? This will be for VM storage backend, so integrity is important. If the answer is that I need sync=always, I'll just gollow @gea's recommendation and buy an Optane 800P for ZIL and call it a day.
I guess the second part of the question is, will the 800P ZIL act as an extended write cache? Meaning if I were to write over 100GB long sequential writes and the backend couldnt keep up, it would just accumulate on the 118GB 800P until it could flush to disk.
I'm setting up a bunch of HGST S840 2TB SAS drives and have been playing around with 6x in a RAID-Z1 to create a 11TB NFS SAN Backend for my ESXi hosts over 4x10Gbe.
With sync=always I get approximately 100MB/sec write speeds on the array. With Sync=disabled I get approximately 200MB/sec.
These numbers seem off, considering I get pretty similar results on a single drive, but I'm going to pull things apart tomorrow and make sure its not performance issues due to PCIe passthrough or other things.
The question I have is, since these disks have PLP in the form of massive capacitors. Do I need to have sync=always, or is sync=disabled fine? This will be for VM storage backend, so integrity is important. If the answer is that I need sync=always, I'll just gollow @gea's recommendation and buy an Optane 800P for ZIL and call it a day.
I guess the second part of the question is, will the 800P ZIL act as an extended write cache? Meaning if I were to write over 100GB long sequential writes and the backend couldnt keep up, it would just accumulate on the 118GB 800P until it could flush to disk.