Hello,
Which RAIDZ should I choose for storing movies/TV shows while maintaining minimal space while protecting data?
I have an SSD for installing TrueNAS.
This month I have two 24TB HDDs and I’ll have two more next month.
thx
With two, the only options are a stripe or a mirror, with a mirror strongly preferred. You can add the other two as another mirror, once you get them.
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With 2 HDDs, 1 HDD copies the data and on the second is a backup?
The same thing with 4 HDDs, 2 storage and 2 backup? With the 4 HDDs, I will have 48 TB of storage?
Take care, have redundancy not mean have a backup.
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Just wait it out until you have the four 24tb drives and do raidz2. Then you can expand one disk at a time because you’ll always need some space eventually.
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Really? How to have a copy like the Synology system (RAID SHR).
Recently, I cut the power supply without turning off the Syno Nas, I had 1 of the 2 disks that had cracked, luckily I had the second one with a copy of data.
@oxyde Do you have a link that explains the different raidZs?
Ty
raidz1 = single parity, similar to RAID 5, minimum 3 drives
raidz2 = double parity, similar to RAID 6, min. 4
raidz3 = triple parity, min. 5
For storing movies on your big drives you’d want at least raidz1 to have minimal protection against incidents, but rather raidz2 to really be able to sustain the complete loss of one drive (I do say “ONE”, not “two”!) and recover without damage.
ZFS does no do “flexible raid” in the manner of SHR. If flexibility is more important than security you might look into Unraid instead.
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You know TrueNAS has docs, right? They’re linked at the top of every page in this forum. They include a lot of information about ZFS, which we’d all recommend you read thoroughly and understand before committing data to your pool.
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https://forums.truenas.com/t/zfs-storage-pool-layout
https://forums.truenas.com/t/assessing-the-potential-for-data-loss
Those guides should cover basis and more.
Also:
Imagine that during the replacement of the failed disks, also the other fails 
and there are a lot of more things that can go wrong in the wrong moment… That’s why you should consider a backup strategy.
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My two cents is to start at the other end of the telescope. You should have a copy on a zfs pool that is entirely separate from your main pool, preferably on an entirely different system off site. ZFS pool on both so you can do replication from your main pool to the backup. Even if the backup is only a single disk on a woefully underpowered system.
Then, once you have figured out the backup, consider how much data you have, and how fast you can get a replacement for a failed drive in your main system. One drive in a stripe fails, you lose everything except the backup. One drive in a two 24tb mirror fails and you can replace the mirrored drive in time, you are ok with 24TB total. One drive fails in a three drive 24 TB Z1, and you can replace it in time, you are ok with 48TB total. Two drives fail in a mirror or Z1 and you lose everything but the backup.
Also, if you have all your movies in one dataset, and all your tv shows in another, it can still take a long time to do the initial replication offsite. (From my primary site, 4 months to do 6TB offsite; so 48TB would be a couple of years) It’s easier to create the second pool on the primary system, replicate, then export the pool and mail it to the second site.
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Thany yoy very much everyone 
So I will point out that you did specifically say you are looking to store movies and TV shows. Assuming you obtained those the way most people do, you could probably obtain them again, just with some hassle. So you may be fine without doing a full backup. Just considere the amount of work it would take to get them back and decide if the cost of a backup is worth it.
If you are storing other, less replaceable data, then you absolutely need to back that up at a minimum.
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Elorimer
That was a Nice Reply to an authentic question. Many times, the always-on-line part of communities like this forgets that even seemingly “Read the Docs” questions need an honest feedback answer, like the one I recently posted, which is essential to me, not to others.
Lowell
Personally, I advise against RaidZ, and recommend a full Mirror myself.
Could be unique to my situation, but I found that the parity calculations caused massive performance degradation when I tried it originally. I run 8x 8TB HDDs.
I’ve been running mirrored configuration ever since.
I also read that when running RaidZ, Resilvering on a drive failure takes a hell of a lot longer, again due to parity calculations.
Mirror also makes expansion a lot simpler too, as you can just add 2 drives at a time as a new mirrored vDev, and call it a day. no hassle.
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I moved to a full mirror, so yes, I lose 94TB of free space but at least I’m safe.
Thank you everyone