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Forum Discussion
RN316 raid options
Just bought a new RN316 6-disk readynas on facebook. Owner bought it new but never opened the box so lucky me. I am not familiar with x-raid and my understanding of raid is more traditional. Also nev...
notspam wrote:
I wonder if I can use flex-raid to create:-
2x 2TB as raid1
2x 2TB as raid1
2x 3TB as raid1
Total 7TB. My goal is redundancy and easy retrieval when one disk is down.
You can do this. You'd need to switch to FlexRAID, delete the existing volume, and then create new ones.
notspam wrote:
I am not familiar with x-raid and my understanding of raid is more traditional
X-RAID uses normal mdadm software RAID underneath - it just simplifies expansion.
4x2TB+2x3TB XRAID would give you an 11 TB volume (the normal capacity rule for single redundancy is "sum the disks and subtract the largest). It would be set up as a 6x2TB RAID-5 group spanning all disks, and a 2x1TB RAID-1 group using the remaining space on the two 3 TB drives. The BTRFS file system is then configured to use both groups, so they are concatenated into a single volume.
Note the NAS uses TiB units when reporting space, so you'd see 10 TB reported for the space with XRAID. 2x2TB RAID-1 would be reported as 1.8 TB, and 2x3 TB would be reported as 2.73 TB.
Both FlexRAID and X-RAID would give you full access to the volume(s) when there is a single disk failure. Your proposed setup would actually handle more failures in some situations, and recovery would be simpler if the volume were to fail. But of course you are giving up some capacity in return.
In general, RAID is not enough to keep your data safe, so you should set up a backup plan.
Also, I always recommend a UPS. That ensures that the NAS will shut down properly if the power fails. Lost (cached) writes can result in an out-of-sync volume(s), and loss of some data.
notspam wrote:
Currently I have 4x 2TB and 2x 3TB in the RN316.
Many mechanical drives in the 2-6TB size range use SMR (shingled magnetic recording). They aren't good choices for RAID, particularly with the BTRFS file system. Write speeds can become glacially slow when you do sustained writes (including the initial volume sync).
Generally WD Red Plus or Seagate Ironwolf are good choices. Enterprise drives are of course also ok. Avoid desktop drives and WD Reds. Both Seagate and WD should identify SMR drives on their datasheets.
One of the features of XRAID (well, really the BTRFS file system underneath) is that all drives do not need to be the same size to fully utilize them (as long as there are at least two of each size). That may differ from your experience with RAID and may make you re-examine your plan. With three separate volumes, you have to allocate content to each one separately, where you don't with one RAID5 volume.
In the event of a hardware failure that corrupts a volume or the loss of two drives, recovery of most of the data would likely be easier with three volumes. But you really shouldn't be relying on RAID for that anyway. Unless what's on there is just backups (it exists elsewhere), then you really should have a backup plan.
And, as StephenB said, XRAID is not some exotic Netgear-unique RAID. It's standard Linux MDADM RAID with a BTRFS file system on top. So RAID recovery techniques for Linux RAID and BTRFS work fine with it. XRAID is nothing more than some logic that does the RAID manipulation, especially expansion, for you. (Nothing more italicized, because I'm sure the logic isn't trivial.)
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