How big should my L2ARC be?
2TB is small enough that it’s plausible to go all-SSD and not need an L2ARC at all.
How big is zil?
A fast platter drive these days can crank out just over 200Mb/s, so a ZIL for an array made from that drive should be about 2-4GB.
What is L2ARC?
The L2ARC is the 2nd Level Adaptive Replacement Cache, and is an SSD based cache that is accessed before reading from the much slower pool disks. The L2ARC is currently intended for random read workloads.
How much RAM does FreeNAS really need?
How Much RAM is needed? FreeNAS requires 8 GB of RAM for the base configuration. If you are using plugins and/or jails, 12GB is a better starting point.
What is L2ARC in ZFS?
The primary ARC is kept in system RAM, but an L2ARC—Layer 2 Adaptive Replacement Cache—device can be created from one or more fast disks. In a ZFS pool with one or more L2ARC devices, when blocks are evicted from the primary ARC in RAM, they are moved down to L2ARC rather than being thrown away entirely.
What is ARC hit ratio?
The ARC is the read cache and the hit ratio is the percentage of reads that come from the cache and not from the drives. So a perfect usage of the cache would give 100% and no cache usage at all would give 0%.
Should I use L2ARC?
In general, if you have budget which could be spent either on more RAM or on CACHE vdev devices—buy the RAM! You shouldn’t typically consider L2ARC until you’ve already maxed out the RAM for your system.
What is persistent L2ARC?
Persistent L2ARC, or L2ARC rebuild, is a ZFS feature that was added to TrueNAS 12.0. By default, the L2ARC cache empties when the system reboots. This is intended to preserve L2ARC performance even after a system reboot.
How much RAM does TrueNAS use?
A minimum of 8 GB of RAM is required for basic TrueNAS operations with up to eight drives. Beyond that, there are use cases that each have distinct RAM requirements: An additional 1GB per additional drive after eight will benefit most use cases.
Is 1GB RAM enough for NAS?
All NAS devices arrive with a portion of memory includes, typically in the form of Gigabytes, and generally around 1-4GB to compliment the CPU and ensure smooth running for general use.
What is ARC in FreeNAS?
The ARC is a cache of data that the server thinks will be accessed next. Since RAM is faster than the HDD, it means that you get better performance. The ARC size is how much RAM is dedicated to the cache. It uses more or less all the remaining memory on the system.
