I have a couple of home built TrueNAS systems for many years (since FreeNAS, ~ 10 years ago), here is some feedback:
- with same disk size, but just 3 disks, I get around 240 MB/sec read speed for large files (with 10 Gbps NIC). I guess the biggest difference is the CPU power, your NAS seems very slow. On 1 Gbps NIC I get 120 MB/sec transfer speed. My system is even virtualized, on bare metal may be a little bit faster.
- you cannot expand your pool, if you add one more disk there is no way to cleanly migrate to a 5 disk raidz1. There is some new development that kind of does something, but it is not what is needed
- unless esthetics is a big deal for you, there are still $30 cases around. The extra $70 can be used for something else *
- * with a small percentage cost increase, an investment in CPU and RAM can give you the capability to run some VMs on that hardware, so that CPU will not sit at idle 99.9% of the time and be underpowered when you do use it. Using a dedicated computer just for a NAS is not very cost and power efficient, but if you group multiple functionalities it becomes a great tool. For example I run 3-4 VMs at all times, up to ~ 12 when I need it.
- that motherboard and the comparison to a B450 is wrong. The MB restricts you to 4 SATA, while the B450 I bought for ~ $120 has 6 SATA ports
- TrueNAS does not *require* a HBA firmware change, that is needed if you want to convert a RAID controller to plain HBA mode or with certain old HBA that need newer firmware. However for your setup a HBA is not needed. If you want to add many disks and have a good performance (like more than 500-1000 MB/sec) then you need the HBA
- your math is wrong. You calculate available space using ~ 3.8TB disks and divide to 4 TB. The 4TB disks don't have 4TB, but 4x10^12 bytes, so the percentages in your table are exactly 80%, 60% and 40%.
- that CPU does not work with 32GB DIMMs. This works only with newer Ryzen generations, not with Zen+ in this CPU.
- GPU is not missing. TrueNAS does not render anything on a GPU, there is no need for one. I did ran TrueNAS for a couple of years on a computer with no video capability at all (a Ryzen 2700) without any problem, I just used a GPU for the initial installation and then removed it.
- unless you store a database for a SQL server or similar, there is no benefit in a SLOG; it is not a tiered cache, so it does not speed up file transfers in any way. You can have a disk dedicated as a read cache, but the cache content is currently wiped at every restart (a documented limitation) and not needed if you don't want very good performance with small files over the network
- with same disk size, but just 3 disks, I get around 240 MB/sec read speed for large files (with 10 Gbps NIC). I guess the biggest difference is the CPU power, your NAS seems very slow. On 1 Gbps NIC I get 120 MB/sec transfer speed. My system is even virtualized, on bare metal may be a little bit faster.
- you cannot expand your pool, if you add one more disk there is no way to cleanly migrate to a 5 disk raidz1. There is some new development that kind of does something, but it is not what is needed
- unless esthetics is a big deal for you, there are still $30 cases around. The extra $70 can be used for something else *
- * with a small percentage cost increase, an investment in CPU and RAM can give you the capability to run some VMs on that hardware, so that CPU will not sit at idle 99.9% of the time and be underpowered when you do use it. Using a dedicated computer just for a NAS is not very cost and power efficient, but if you group multiple functionalities it becomes a great tool. For example I run 3-4 VMs at all times, up to ~ 12 when I need it.
- that motherboard and the comparison to a B450 is wrong. The MB restricts you to 4 SATA, while the B450 I bought for ~ $120 has 6 SATA ports
- TrueNAS does not *require* a HBA firmware change, that is needed if you want to convert a RAID controller to plain HBA mode or with certain old HBA that need newer firmware. However for your setup a HBA is not needed. If you want to add many disks and have a good performance (like more than 500-1000 MB/sec) then you need the HBA
- your math is wrong. You calculate available space using ~ 3.8TB disks and divide to 4 TB. The 4TB disks don't have 4TB, but 4x10^12 bytes, so the percentages in your table are exactly 80%, 60% and 40%.
- that CPU does not work with 32GB DIMMs. This works only with newer Ryzen generations, not with Zen+ in this CPU.
- GPU is not missing. TrueNAS does not render anything on a GPU, there is no need for one. I did ran TrueNAS for a couple of years on a computer with no video capability at all (a Ryzen 2700) without any problem, I just used a GPU for the initial installation and then removed it.
- unless you store a database for a SQL server or similar, there is no benefit in a SLOG; it is not a tiered cache, so it does not speed up file transfers in any way. You can have a disk dedicated as a read cache, but the cache content is currently wiped at every restart (a documented limitation) and not needed if you don't want very good performance with small files over the network