HDD integration

[cloudfire]

Hi everybody,

I'm new to this community and just ordered the parts for my first freenas system.

I have 2x 3tb new disks and 2x 3tb disks with data already on it. I would like to end up with a 4 disk raidz2 with the data on it without buying more disks or upload and download 6tb to some temporary space.

Is this possible? Any support is appreciated.

 

[joeschmuck]

No, you will not be able to take your two drives with data on them and simply add them to the system. You will need to copy all the data off to another location and then create a new pool with the four hard drives (this will format them all) and then once you have sharing enabled and such, you can copy your data to the pool. Also realize that you cannot add a single disk to the pool to expand it, ZFS does not work that way. Honestly, you should haev done some reading about ZFS and how FreeNAS works before buying the hardware. Hopefully you realize that you will have ~4.4TB of usable space on this drive setup. This is 80% of the usable pool size in order to ensure the pool operates at a fast speed. If you desire more space then it's best to add more space now. Each 3TB drive will give you about 3TB more capacity from this point on (roughly).

 

[cloudfire]

Thank you for your response, even though I missed the right sub forum.

I already read some, but was hoping there would be a workaround to get hdd's into the pool without loosing the data on it. After your post I read some more and now have decided to start with 6 disks right away, even though I do not need the space right now.

I still wonder, about your ~4.4TB usable space statement, since the raid capacity calculator tells me that I would have 6 TB usable. Maybe you meant that on a 3TB HDD I actually have around 2.7 TB which leads to ~5.4 TB usable space?

 

[cloudfire]

@joeschmuck: I just looked through your system specs and saw that you use the Supermicro X11SSM-F, which I also chose. I wonder that you use SATA PCI-E Cards while you have 8 sata ports and use no more than 8 disks. Is there any advantage in general or with this board that one should not use the onboard ports?

 

[joeschmuck]

With respect to the X11SSM-F SATA ports, I am using ESXi, meaning I run FreeNAS in a VM so i need to pass though ports which is why I have the add-on cards. I cannot do that with the motherboard ports, well not the way I want to. If you are running FreeNAS on bare metal then the SATA port on the motherboard are fine.

With respect to the RAID calculator...
Four 3TB hard drives in a RAIDZ2 configuration gives you 5.5TB of storage.
Reduce 5.5TB by 20% (5.5 minus 1.1) and you are down to 4.4TB of storage.
Reduce 2GB from each drive for the SWAP file which is automatically created, now you have ~4.4TB (minor difference but worth mentioning).

The 20% reduction is so you never exceed 80% full. When you exceed 80% full then the file operation slow down a bit. The real slow down occurs at 90% full where the file system switches into a write optimization mode and you will notice it. Now if you are only watching movies on your syste, exceeding the 80% rule is not an issue, but the 90% value will likely be an issue. Backing up a bit, the 80% rule is basically, so long as you are under 80% then your pool is considered healthy. I promote the 80% rule because if someone hits that, odds are they will get to 90% and things slow down and they will create a posting asking why the system slowed down. They forget about this 90% write optimization mode.

I hope that clears things up.

So if you have six 3TB drives in a RAIDZ2, you end up with 10.9TB - 2.18TB = ~8.72TB of usable space (80% rule).

Now to throw one more thing at you... by default LZ4 compression is turned on. This means that if you have any files which can be compresed, you will be able to store more data. This is done behind the scenes so it's a benefit. If the file is a video or zip file, those likely cannot be compressed so the file is just stored. Keep this in mind as well, at times it feel like a Christmas gift when you examine your data.

 

[cloudfire]

I just stumbled over a way to achive my goal to get disks with data into a raidz2.

I know it is not the clean way, but should be mentioned as possibility.

First step is to setup a degraded raidz2 with 2 disks missing. If the degraded raidz2 is up, copy data from the 2 drives to it. After copying the data add the 2 drives which get resilvered and change my raidz2 to a normal state.

edit: I just found a post with the commands: https://forums.freenas.org/index.ph...dz-3-of-4-drives-i-e-to-allow-migration.7748/

 

[Vito Reiter]

I just stumbled over a way to achive my goal to get disks with data into a raidz2.

I know it is not the clean way, but should be mentioned as possibility.

First step is to setup a degraded raidz2 with 2 disks missing. If the degraded raidz2 is up, copy data from the 2 drives to it. After copying the data add the 2 drives which get resilvered and change my raidz2 to a normal state.

edit: I just found a post with the commands: https://forums.freenas.org/index.ph...dz-3-of-4-drives-i-e-to-allow-migration.7748/

If you can take this risk, then it sounds like you're in a position to start from the ground up anyway. With the amount of I/O's that will happen during the data transfer process, your risk of failure will surely increase 10 fold, especially in a degraded state. If you don't want to lose data, I would find another way to achieve that goal. A while back I used some smaller disks temporarily, just so I had the amount in my array that I wanted to end with (in your case 6). Then I cloned the data to the new volume and resilvered those small, terrible drives, with the drives that had previously stored the data.

 

[joeschmuck]

Yea, I don't like this method but if you understand the risks then it's okay. Keep in mind that the risk is once you finish copying the data and you add back the 2 drives into the pool, a failure of one of the original drives would make all your data be gone. It's not a huge risk but it is a risk none the less. I'd find a better way to do it myself unless it was just movies and stuff I didn't casre about loosing.