A filesystem and a cache question before my unraid journey starts

[___niko___]

The Plan
Attached a picture of the old and new setup

The Rationale
I'm about to embark on my first unraid project.
Drives and electricity cost at lot of money over here in the EU, so I decided to give my several machines that I already have a different purpose to optimize usage and cut back on power-costs.
Although I like ZFS and snapshots combined with TrueNAS, it's not as flexible as unraid with the mixed size drives.
Overall plan is to have my unraid machine do its thing once a week and then turn it off at the end of the day.

The Questions
I have plenty of experience with TrueNAS and watched a lot of spaceinvader's videos but before I begin on my unraid journey, really need help with 2 decisions.
1) filesystem: XFS/ZFS. Unraid now seems to be firmly aboard the ZFS train but for my usecase I don't think ZFS has much extra use. Snapshots also take up space and for bitrot I have the parity drive(sort off). Have mostly movies and family pictures which are already compressed so not missing out a lot there either.
I'll lose the snapshots but I've read that rsync can copy over all files retaining dates/permissions etc so not hung up on that. 
So my take would be using XFS, if I've missed any compelling reason not to use XFS please let me know.
 

My plan is to start with 2 drives then putting some selected data drives in the unraid server to locally copy the data onto the array. Once finished, wipe the data drive and then make it part of the array expanding the capacity to where it can hold all the data from the different sources. After the copying is done, add the parity drive.
2) Should I use a cache SSD during this first period of just copying data onto the array or better to wait once everything is in place and THEN add a cache drive to cache new writes before committing them to the array?

Thanks for reading!

Edited December 15, 2023 by ___niko___
fixed some typos

[___niko___]

Talked to @Pri on Discord and got these answers:

Question 1: use XFS for disks in the unRAID array, it's tried and true, reliable.
Question 2: Don't set your shares for files to use the cache drive until after you've migrated all your data, it will be a lot faster and stop your cache from hitting 100% capacity before Mover is invoked. Also SSD's have a finite amount of write cycles so it's a good idea to leave them out of the initial onloading of your data from your previous system for longevity too.
Thank you @Pri

[itimpi]

Note that parity is not a substitute for backups as it only protects against dtive failure - not other ways of losing data.    For anything important you cannot afford to lose you need a backup that is not on the server (and ideally off-site).

 

[___niko___]

On 12/23/2023 at 1:13 PM, itimpi said:

Note that parity is not a substitute for backups as it only protects against dtive failure - not other ways of losing data.    For anything important you cannot afford to lose you need a backup that is not on the server (and ideally off-site).

 

Thanks @itimpi as I showed in the picture, the data on the unraid server to be used IS the backup data already.
The most important stuff is also replicated to an offsite NAS using RCLONE.