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Readynas 314 adding new hard drives
Hi I had 2x2TB hdds installed in my 314 with RAID1 setup. I wanted to add 2 new hdds with 4TB capasity so I just added two disk in and it started to sync. Now when syncing is ready it shows that ...
StephenB wrote: If you leave it as RAID-5, the volume will expand to 6 TB (5.45 TiB) after you add the two new disks. ...I missed that you were adding 4 TB drives. RAID-6 isn't actually possible (the four largest drives all need to be the same size).
XRAID will give you an 8 TB volume (~7.27 TIB). The capacity rule is "sum the drives and subtract the largest". After the expansion, you'll be able to replace a failing drive with one of the same size, or with one that is larger than 4 TB.
Sandshark gave you the technical explanation of how this works. As he says, you'll end up with a RAID-5 group of 4x2TB (6 TB capacity) and a RAID-1 group of 2x2TB (2 TB capacity). These are concatenated into a a single 8 TB data volume.
XRAID will protect you from routine drive failures (of any of your drives). But RAID in any form isn't enough to keep your data safe - devices (and redundant RAID arrays) can still fail. So if your data matters to you, you do need to back it up onto at least one other device. USB drives are a cost effective way to do that. The array isn't protected during expansion, so I recommend backing up your data before you hot-insert the first new drive.
thanks for your reply
I'm a really newbie, maybe thats why :)
So in RAID5 2TB hdds are clone together and 4TB hdds are also clones? So if 2TB hdd fails the other one has the same data inside (and 4TB are the same)?
Or how my data is protected in RAID5?
Why two RAID1 volumes is only 4TB? So it's not that 1 volume of 2TB and other RAID1 volume of 4TB.
XRAID is a kind of "layer cake".
Starting with 2x2TB and adding 2x4TB will first add a 2TB partition of each 4TB drive to the existing 2TB drives, converting it to RAID5, so you get 3x2TB of usable space and 2TB of redundancy in that layer. Then, it will create a RAID1 from the remaining 2x2TB from the 4TB drives, with 2TB of usable storage and 2TB of redundancy. The file system will span the two RAIDs, invisible to you. So, you get a single volume of 3x2 + 2x1 = 8TB with XRAID. If you had 1 RAID1 of 2x2TB (2TB usable space) and one of 2x4TB (4TB usable space), you would have only 6TB, and it would be in two separate volumes. You can do that in FlexRAID, but you would have had to switch to that before adding the drives. XRAID gave you the most efficient use of your new drives.
Each layer must consist of partitions the same size. That's what limits adding smaller drives to a RAID (unless there previously were similar small drives), a large enough partition for that layer cannot be created on them. And each partition must have a mate for at least a RAID1, which is why the first drive of a larger size isn't fully utilized til it has a mate.
BTW, none of the methods used to actually create this layer cake are proprietary. The proprietary part is the smarts that figures out for you what to do with the added drives. It does lead to some limitations in expansion (adding smaller drives being one of them, it actually could be done, though not efficiently) so that the logic doesn't become too convoluted for the next step to be determined.
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