SSD Boot Drives - Mirroring and Cache query

[Harrisonm65]

Hi everyone.

Very VERY new to all this so please, be gentle!

Im in the midst of repurposing some old kit to build a small FreeNAS for home use only. I'm using 2 new 120GB SSDs which first of all I was looking to mirror. I heard that its best to let FreeNAS do this rather than using any onboard RAID setup to do so. My question is, how does that work? When installing and you are asked to pick a destination drive, whats the process of mirroring them please?

Also, and this might be a bit more involved, as the installation barely uses any space, I was wondering if the drives could somehow be partitioned? Use a small part of them, say 20GB for OS installation, then the rest as a cache for some other purpose. Is it even worth doing that? Any advice would be greatly appreciated.

Thanks in advance.

 

[Yorick]

When those are your boot drives, what will be your data drives? And no, partitioning those is more trouble than it's worth, particularly when you're just starting out. Not to say it can't be done, but the utility is questionable, and why go there.

 

[Harrisonm65]

When those are your boot drives, what will be your data drives? And no, partitioning those is more trouble than it's worth, particularly when you're just starting out. Not to say it can't be done, but the utility is questionable, and why go there.

Im still looking at data drives and weighing up the cost v reliability scenario of standard desktop drives v NAS specific drives. Im decided on 4 to start off with though in a ZFS2 configuration.

 

[Yorick]

Thanks for explaining! ZFS will allow you to mirror those drives when you install. You'd install from USB, onto those drives. Yes, make sure your motherboard SATA is set to AHCI, turn off all RAID functions.

For your drives: You want to avoid DM-SMR, see Resources. Desktop drives use that more commonly; in NAS drives, the WD Red 2-6TB are DM-SMR now, so avoid those.

Im decided on 4 to start off with

I'm going to read into what you said: You want to expand this in future. Keep in mind that you can add another 4-drive or N-drive raidz2 vdev; you can replace all drives in your 4-drive raidz2 vdev with higher-capacity ones; you cannot add a drive to make your 4-drive raidz2 a 5-drive raidz2. In Resources there's an Introduction to ZFS. If you haven't read that, do, or read the intro in r/zfs, which is also good.

 

[Harrisonm65]

Sweet. Id read about the different vdevs etc but I'll check out Resources too to get myself as fully up to speed as poss. Its only a small home build in an old mid tower case, so cant add too many drives anyway, but handy to know you cant add extra physical drives to an existing vdev.

Just to confirm too - once I start the installation sequence from my bootable USB (already created), I will have the option somewhere to mirror the 2 SSDs and install onto that? Provided I leave all motherboard options for RAID disabled etc of course.

 

[Yorick]

Yup, I seem to remember that you get the option to install onto a mirror. You can also mirror after the fact, though I do not know how that behaves with regards to boot sectors on both drives.