2 HHD Unraid with no Parity - Need Advise

[zeekay]

Hi Folks,

 

I am building my first unRaid server. This will be a backup storage. I have a Synology DS918+ as my main NAS. I'll use this new unRaid to:

Create a complete backup of Synology NAS

Run containers, VMs and some other tools 

 

My Synology NAS has 14TB of complete space, about 1/3 is full right now, growing steadily. 

The unRAID is built with 2 x 18TB HDDs and 2 x 4TB NVMe SSDs. I am thinking of setting up unRAID

HDDs in RAID1 config with a total capacity of 18TB available. This will easily backup my Synology and will still have room.

NVMe SSDs with JBOD config (RAID0 ?). This will be my high speed storage and will be fully backed up on the 18 TB HDDs. I might run a little over capacity on HDDs, but I'll monitor to make sure that I'm not maxing out my pools. Also note that NVMes will host non-critical data so loss is not a problem.

Having said that, I was thinking of setting up unRAID without the parity drive, because this is mainly backup. Several articles say this is not an issue.

Can you guys opine on this setup, given my requirements.

Also, if one of the HDD fails completely, how will I recover my data? I'm thinking that unRAID will continue to run with only one HDD until the faulty one is replaced and then it'll rebuild the RAID1 mirroring. But I could be wrong.

 

Thanks in advance!

ZeeKay

[itimpi]

Note that if you have 1 data drive = 1 parity in the main array this is a special case where the drives are mirrored, but that would not be the case if later additional data drives were added.   Also, it is the Unraid specific handling of parity - not traditional RAID1.  It is better to think of 1 parity drive being able to handle 1 physical drive failing.

 

if you want true RAID1 then you can instead set up a 2 drive pool (using BTRFS or ZFS).

 

if a drive in the main array fails then Unraid will continue to operate as if it was still present, using the combination of the parity drives and any non-failed data drives.

 

running without parity is a perfectly viable strategy if this is a backup server.   It just means that if a drive fails then there might be a big copying task required to get the backup server up-to-date again.

 

[zeekay]

On 6/23/2023 at 8:01 AM, itimpi said:

Note that if you have 1 data drive = 1 parity in the main array this is a special case where the drives are mirrored, but that would not be the case if later additional data drives were added.   Also, it is the Unraid specific handling of parity - not traditional RAID1.  It is better to think of 1 parity drive being able to handle 1 physical drive failing.

 

The case I have only takes two 3.5 HDDs, so I wont be adding any more drives to it. So this will be my final configuration.

 

On 6/23/2023 at 8:01 AM, itimpi said:

 

if you want true RAID1 then you can instead set up a 2 drive pool (using BTRFS or ZFS).

 

if a drive in the main array fails then Unraid will continue to operate as if it was still present, using the combination of the parity drives and any non-failed data drives.

 

Since there will only be two 3.5 HDDs, there wont be a parity drive. So how will failure of one drive look like?

 

On 6/23/2023 at 8:01 AM, itimpi said:

 

running without parity is a perfectly viable strategy if this is a backup server.   It just means that if a drive fails then there might be a big copying task required to get the backup server up-to-date again.

 

 

Copying task? Can't I just replace the failed drive and let the BTRFS rebuild itself?

[zeekay]

On 6/23/2023 at 8:01 AM, itimpi said:

 

if you want true RAID1 then you can instead set up a 2 drive pool (using BTRFS or ZFS).

 

 

So how does it work? Should I not add the two 3.5 HDDs to the array then?

If not, then use the pool option below that?

Will I be able to create shares and everything on the BTRFS?

[zeekay]

Ok so If i add both the 3.5 HDDs to the array and then select BTRFS as filesyatem, there is no option to select one drive to mirror the other. However, I can add one 3.5 HDD to the parity while use the other in the array. Does that accomplish RAID1 config in unRAID with two drives?

 

What am i doing wrong?

[JorgeB]

You can either assign one disk to parity and one to the array creating a raid1 mirror or create a raid1 btrfs/zfs pool, the latter requires at least one data device assigned to the array, can be an old flash drive.