We upgraded Truenas server RAM to improve performance, heres why...

After monitoring the ARC hit ratio as per our last article, we’ve upgraded a clients storage server (Truenas) RAM to improve performance.

Originally the server had 64GB of RAM which is a good starting point to use with ZFS. As we discussed before, ZFS loves RAM. However, after monitoring the ZFS stats that Truenas gives us we noticed a low ARC hit ratio (and slower than expected performance) and have since upped the RAM to 128GB and have now not got mean hit ratios in the >90% which is great!

This storage server serves several virtual machine disks through NFS shares, so having a high ARC hit ratio means that most of the virtual disks are running from ARC rather than disk resulting in much better VM performance. Using the virtual machines you would just guess that it was running on SSDs, not 8TB disks.

So ZFS allows us to get the economy of spinning disks but through ARC (a.k.a RAM) much better performance, a bit like that of SSDs. This, I think, is good value for money as the RAM was 1/6th of the cost of turning to an all SSD server.