JTBurton wrote:JBOD - biggest capacity but if one disk dies I lose the lot (is that right?)
RAID 1 - a bit faster (?) and guards against a disk failure at the expense of losing a disk's capacity
RAID 5 - no performance gain, but guards against a disk failure at the expense of losing a disk's capacity
As stated above. Some people regard RAID as a red herring and that it's completely over the top for home use. However, I certainly want as little hassle as possible in recovering from a failed disk or unit.
Also consider the Synology Hybrid RAID format, also called "Standard", as this will be presented by default I tink in models with more than 2 bays. The disadvantage of the above RAID formats is that your capacity is restricted to the size of the smallest disk. This is not a major problem with 2 disks in RAID 1, however if you've got 4 disks in RAID 5 and you decide you need to increase your capacity, you have to replace ALL of your disks with bigger ones before you gain anything. SHR uses a combination of RAIDs to provide multiple partitions, but it is completely transparent and it just looks like you've got one volume. But with SHR, you benefit immediately by increasing the size of just one disk. SHR will maximise the use of the disk space that you have available. The disadvantage is a 10% loss in performance.
I currently have a DS209 with two 1TB disks in RAID 1. This is intended to be a dedicated backup server, to back up the contents of my 2 PCs, also my media files. RAID 1 might be over-the-top for a backup device, but what happens if you need to retrieve a file from backup and then find your backup disk has crashed? Not hugely likely to happen, but can you afford to take the risk, it's a choice only each individual can make!
I'm also toying with the idea of a 4-bay NAS which will be an always-on device, for serving media files and perhaps for general network storage, moving My Documents from the PCs onto it for example. I will start with 2 disks in SHR (I want SSDs...), then add more when prices drop and capacities increase. If one disk fails, then I can simply replace it without having to restore from the backup server - as the last backup might not be current enough. Note that a single RAID system like this does *not* safeguard against accidentally deleting files or corrupted files.
So data security/safety has two considerations:
1. Availability of data and not losing *current* data if a disk fails. This implies a main filestore in some sort of mirrored configuration, i.e. RAID.
2. Ability to go back to any backup in the past to restore lost or corrupted files. This probably implies a separate backup device from your main filestore to which you back up at regular intervals.
In which case, how do I backup the NAS except with another NAS? Can I backup the NAS media folders to the NAS itself, which is a bit of a crappy strategy.
Yes, you can do this, but as you've realised it's not *completely* foolproof. If the RAID fails, or the unit fails and corrupts the data and is not recoverable, you've lost everything. With a 2-NAS strategy, you've lost your current data but at least can restore from the most recent backup.