Please correct / add input to the following. I'm trying to make sure I have all my hosts built-out with parts, and want to make sure 100% I understand my devices needed for L2ARC and SLOG.
ARC Configuration
- Provide as much RAM for ARC as possible for best performance
- You can't designate ZFS ARC max usage per-pool.
- You can designate ZFS ARC max usage but it was deprecated in 2014, you can also now configure % to utilize so some is reserved for other OS duties.
- (If using) The value for vfs.zfs.arc_max needs to be smaller than the value for vm.kmem_size (not only ZFS is using the kmem).
L2ARC Configuration
- L2ARC drive suggestion are MLC SSD, low latency drives.
- Using a L2ARC device will increase the amount of memory ZFS needs to allocate
Can you share L2ARC between pools?
No.
SLOG Configuration (Sometimes called ZIL)
- You can have a SLOG or slog-pool per-drive pool in ZFS.
- Best performance is most likely gained from a SLOG POOL of 2 devices (RAM or SLC SSD).
- Sized 2-8gb seems to be very common
-- This could be important if you wanted to use SSD for Spinning SLOG Pool and RAM for SSD SLOG Pool.
- Larger SSD while not needed often have much higher performance and can be utilized for LARGE over-provisioning, and maximum performance, although they cost more.
ARC Configuration
- Provide as much RAM for ARC as possible for best performance
- You can't designate ZFS ARC max usage per-pool.
- You can designate ZFS ARC max usage but it was deprecated in 2014, you can also now configure % to utilize so some is reserved for other OS duties.
- (If using) The value for vfs.zfs.arc_max needs to be smaller than the value for vm.kmem_size (not only ZFS is using the kmem).
L2ARC Configuration
- L2ARC drive suggestion are MLC SSD, low latency drives.
- Using a L2ARC device will increase the amount of memory ZFS needs to allocate
Can you share L2ARC between pools?
No.
SLOG Configuration (Sometimes called ZIL)
- You can have a SLOG or slog-pool per-drive pool in ZFS.
- Best performance is most likely gained from a SLOG POOL of 2 devices (RAM or SLC SSD).
- Sized 2-8gb seems to be very common
-- This could be important if you wanted to use SSD for Spinning SLOG Pool and RAM for SSD SLOG Pool.
- Larger SSD while not needed often have much higher performance and can be utilized for LARGE over-provisioning, and maximum performance, although they cost more.