Edited by tkaiser at Fri Nov 21, 2014 09:00 |
cyryllo replied at Fri Nov 21, 2014 06:23
Of course you can build a really good NAS Raid on the board as provided
Unfortunately this is not true. When you deal with TBytes of storage 'good old' RAID-5 isn't sufficient any longer due to just single redundancy and the statistical failure rates that put your whole array at risk! It's a simple fact. So you need at least double redundancy and that means RAID-6 or similar. And then just 4 drives do not make that much sense.
Using an el cheapo port multiplier as one central single point of failure between host controller and disks does not only mean horribly slow performance in general but also putting your data at even higher risk: 1) if a disk fails -- or the RAID implementation thinks so -- and a rebuild is started and now the PM does something wrong all data is gone instantly. And 2) due to the bad performance the rebuild will take ages which means that meanwhile no other disk is allowed to fail otherwise all data is gone. This alone thwarts the whole RAID approach completely.
If availability / business continuity is a concern (which it isn't at home!) then you have to do it right. And then you should also think about data integrity and that means using a modern file system that implements end-to-end data integrity utilizing checksums over the whole data paths. Which is pointless on 'tablet grade' hardware that lacks at least simple ECC memory.
So the minimum hardware requirements to do RAID correctly if you want to enhance availability and want to care about data integrity (and also want low power consumption, less noise and so on) is at least something like Gigabyte GA-9SISL, SuperMicro A1SAi-2750F or when many disks should be used ASRock C2750D4I or SuperMicro A1SA7-2750F. These octacore avotons with support for large amounts of ECC RAM are fast enough for a lowend RAID. And then you would use eg. FreeBSD or Solaris with ZFS/raidz2/raidz3 to build a reliable RAID implementation featuring also data integrity and that will not fail in 'worst case' scenarios.
And nothing of this addresses even remotely 'data safety'. This can only be done using a separate storage implementation using versioning (no direct mirroring!). RAID won't help here at all.