RaidZ2

[zubbs1]

Apologies if this is the wrong section for this.

Current setup contains 2x 4TB, 1x 3TB, 1x2TB, 1x1TB. All drives are flying solo without any sort of array pool. I am manually mirroring folders of data across the drives so that everything important to me has a second copy on a separate drive. I want to create a more robust and efficient system, I think using a RaidZ2 array is the best option. The plan is to buy another 2x 4TB hard drives, and a SATA controller card (link). I will move the 2TB and 3TB drives to the controller card ports, and join them into a JBOD pool. The 4x 4TB drives I want to form into a RaidZ2 array.

I believe If I want to include the two 4TB drives I currently have into the 4x 4TB drive pool I create, will I lose all the data on those 4TB drives. If that is the case, what is the best way to accomplish my goal?

 

[Ketchup]

I don't understand why you want a jbod array. The only thing they do is help you share a drive letter among multiple disks, which isn't going to help with having a backup. Also RAID is only a short-term solution. Do you already have all important data stored outside the computer as well?

You are correct that creating a RAID array of any type will wipe any data on the drives involved.

 

[zubbs1]

I don't understand why you want a jbod array. The only thing they do is help you share a drive letter among multiple disks, which isn't going to help with having a backup. Also RAID is only a short-term solution. Do you already have all important data stored outside the computer as well?

You are correct that creating a RAID array of any type will wipe any data on the drives involved.

I have about 6TB of data that I want secure. I thought that a RaidZ2 was second best to only a RaidZ3 for this? Sure I could buy x number of external hard drives for backup, or x^2 flash drives, but I am then still relying on a single drive for this security (and spending more money in the process vs. internal storage). The RaidZ2 would give me two disk failure redundancy with ~8TB of storage to increase my available storage. Am I missing something here?

So what is the best way for me to achieve getting my data into this 4x 4TB array, without losing it?

The JBOD is just to give one pool of data for two drives that still work fine and I don't want to throw out. I don't intend on putting data on these I'm not willing to lose.

 

[Ketchup]

For zero down time and short-term backup, use raid. For true backup, use drives outside of the machine. Then set you schedule.

As far as type of array, I wouldn't be the best one to ask. But I do like what I had read about the speed and fault tolerance of Z2.

 

[ethebubbeth]

Caveat: I don't see you talking about performance needs in your post.

I personally wouldn't use RAIDZ2 for four drives.

With RAIDZ2, you lose 2 drives worth of space to parity data, or 50% of a 4 drive array. An advantage is that you can lose any two drives in the pool and still be online.

With four drive's, I'd rather make a vdev that's a mirror of two drives as one vdev. Then, create another vdev that is also a mirror of two drives, an put them into one pool. The space lost is the same 50% of a four drive RAIDZ2. You are slightly less resilient in that you can lose one drive from each vdev and still be online, not any two drives. You will lose the data in your pool if both drives in a mirror fail at the same time.

However, When you make a RAIDZ, Z2, or Z3 vdev, you are limited to the write performance of one drive in the vdev due to the way the parity is distributed across drives. You would get one drive worth of write performance for four drives.

With the double mirror vdevs, you have two drives worth of write performance in the pool, and a heck of a lot more read performance since all data is on both drives in the array, without having to do anything with parity.

In summary, RAIDZ2 is more fault tolerant because you can lose any two drives from the pool, whereas two mirrors will lose data if both drives in the same mirror fail, but will be much more performant.

Edit: Yes, if you put drives into a new vdev, they will lose their existing data