Hi,
I would like to ask for advice on how to best use 2xHDD (3TB) and 1xSSD (2TB).
What I want to achieve is fast access to data and ensure security. I have 0.5TB of data that is critical to me.
What is the best way to create a storage pool?
I have the option of adding an additional SSD drive, but only in size 2230 or 2242. But such drives are quite expensive (e.g. WD SN770M).
You need a boot device. A small and cheap SSD in M2 2230 or 2242 would be well-suited for this function, as the port has otherwise little use.
Two HDDs make a mirror. You could add the SSD as a third drive (3-way mirror) for extra redundancy but that would waste both the extra size of the HDDs and the speed of the SSD; so there’s no real use for this SSD.
For security, as always: Have backups! “ZFS is not a backup.”
(If your critical data is 0.5 TB, you could put the SSD in an external enclosure and use it as external backup, possibly even internally redundant backup by taking a page from @Arwen 's book and setting copies=2, or even partitioning it to make a raidz1-in-one-drive.)
Thank you for your answer.
I don’t want to use HDD drives as primary due to slow access (especially when using containers).
So it would be best to add a second SSD, create two storage pools and do SSD to HDD replication?
As for the system drive, I’m thinking about using an industrial USB Transcend JetFlash 180I.
You did not specify that.
So use the SSD as non-redundant application pool, but keep your critical data on the HDD mirror pool. Critical → Redundant
You can backup the app pool to HDDs.
And the backup the HDD elsewhere.
This may work, but a small 2242 M.2 will likely be cheaper.
Do NOT use a USB Flash drive as a boot drive - there are too many writes for a Flash drive which will very quickly die.
Everyone else will tell you not to use a USB SSD for booting, but as someone who actually uses one, I can advise that it isn’t as bad as you think - but you may have frequent or occasional disconnects which cause TrueNAS to hang, the frequency will depend on the reliability of your USB port.
However, @etorix’s suggestion for using the NVMe slot as a boot drive makes much more sense.
Alternatively, use your current SSD as a boot drive, but when you install it use the documented method to only use the first 32GB for the boot-pool and use the remainder as an (unmirrored) SSD-pool. This isn’t recommended because it makes life more difficult if you need to rebuild your boot-pool by reinstalling, but it works just fine.
Or perhaps buy a replacement MB with more SATA ports.
You can consider whether you can afford to have the SSD unmirrored if you replicate it to your HDD pool.
Here are a few options for your disks when you only have 3x SATA ports:
Buy a 2nd SSD, and use a mirrored pair as your primary pool, and a single HDD as a replica backup of the SSD and / or for downloaded files that you can easily download again.
Use the SSD for your primary storage, and stripe the HDDs as a non-redundant 6TB storage for a replica of your SSD and for storing downloaded files which you can afford to lose.
