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[Yggdrasil]

When setting up the DNS-323 for RAID 1, I am asked how much space I want to allocate to RAID 1, the balance being allocated to JBOD.

I have 2 1 TB discs.

If I allocate 500 GB to Raid 1, is the backup info I write to this duplicated separately on each disc, using 500GB of each physical HDD?
I want to ensure that I get the redundancy benefit of RAID 1 , even though I am not configuring the entirety of the 2 discs as RAID 1.

(I assume the leftover JBOD ~ 1 TB is distributed over both discs)

Thanks in advance.

[fordem]

First - I'd like to make sure you understand the "redundancy benefit" of RAID1 - your data remains available with no interruption in the event of a drive failure - how important is the uninterrupted availability when the stored data is a backup?

To deal with your question ...

Yes - with RAID1 whatever information you write is duplicated "separately" (is that an oxymoron?) on each disk, using whatever capacity you set aside for RAID1, and any remaining capacity is used to create a JBOD volume.

Something else I'd like to draw to your attention.

In the event of a disk failure, any data stored in the JBOD volume will be lost, regardless of whether it was stored on the failed disk or not, and when you replace the failed disk, the JBOD will not be recreated, so the only way to recover that space will be to reformat the drives.

My advice is to think twice before using JBOD (or RAID0) - the only benefit to be had from either of these configurations is the available contiguous storage space - do you really need it?

[Yggdrasil]

Thank you Fordem for your response!

I am using the DNS-323 thus:

1) to hold Acronis disc image backups for 4 computers.
Backups are scheduled once per day.
I need less than 500 GB for this purpose.
I felt more comfortable with RAID 1 simply because it gives me two backups, one on each drive.
I don't need uninterrupted availability.

2) I am also using it as a media server, but RAID 1 is not important to me for this purpose. So it occurred to me that assigning 500 GB on each drive to RAID 1, would leave me 1 TB JBOD for other purposes; doing a complete RAID 1 would leave me half that - 500 GB JBOD - for other purposes

From your response I draw:

a) I may not need RAID 1 at all
b) if I had to choose & did not need the extra 500GB JBOD space, configure as pure RAID 1.

Am I missing anything?

Thanks,

Frank

[fordem]

Personally - I don't see the need for RAID1 to store a backup, especially when the backup is of a computer that does not in itself have a RAID1 disk subsystem.  If the disk in my computer fails, that system is down, and the fact that my backup is on a RAID1 device and continuously available even if a drive on the backup device fails doesn't help me any.

Consider instead using separate volumes and put your Acronis backup on one volume and then once a day backup that Acronis backup to the other volume - in the event of a computer hard drive failing (or other data loss occuring) at the same time the drive in the DNS-323 failed, you would have an additional level of protection.