Hello,

I am running ZFS on RAM disk using brd module (/dev/ram0). The RAM disk is
150GB.

Here is my config:

zpool create -O atime=off  -O dedup=on  -O sync=disabled mypool /dev/ram0

the performance I am getting is about 186MB/s sequential write.  I was
thinking I should be getting more than this writing to RAM with ZIL
disabled.

I have also tried this config:

zpool create -O atime=off  -O dedup=on  -O  primarycache=none -O
 secondarycache=none  -O sync=disabled mypool /dev/ram0

This config resulted in much worse performance.


- Should primarycache/secondary cache be disabled on RAM disk? If so, why
did I see worse performance with them disabled
- what other RAM disk block devices I can try in Linux? I am aware of zram
and rapiddisk
- what module options would be helpful to optimize for RAM disk?
- should I limit ARC, and if so how much?
- is there still a per VDEV IOPS limit? I only have 1 RAM device in the
pool that is 150GB would it make sense to do a stripe across several RAM
disks?
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