searching raid 6 card working with fedora 23

[Gordon Messmer]

On 02/01/2016 08:33 AM, thibaut noah wrote:
> Yeah i saw some build reviews on freenas, they recommend ecc but it is 
> not mandatory (and actually after reading some tests i don't get all 
> the fuss on ecc ram).

Just as with disks, bits can flip in RAM.  Probably the most important 
feature of ZFS is checksums on all blocks so that bit flips can be 
detected and repaired.  ECC RAM does the same for memory.  If you don't 
have ECC RAM, and bits flip in memory, you're likely to silently corrupt 
data.

> Saw that too and i don't get it, i mean, what the hell? You can 
> replace disks with bigger one but you'll have all this trouble if you 
> want to expand the array? That doesn't feel right.

The same is true of any disk array, I'd think.  If you replace a disk, 
you need to rebuild the array.  The array size is determined by the 
smallest member in the array.  Given those two constraints, there's 
nothing unusual about the process.

> Thing is spending 600+$$ on a nas doesn't seem worth it compared to 
> buying an high end raid card.

ZFS (and btrfs) and hardware RAID are not, in my opinion, comparable.  
RAID arrays don't keep checksum information on each block, so if a bit 
flips they don't have a means of reliably repairing it.  ZFS can repair 
bit flips.  You probably don't want to use ZFS on hardware RAID, since 
many of ZFS' features rely on accessing each disk individually.  A 
battery backed write cache can be useful, but I don't think it's better 
than having a UPS that's monitored.

> Also it's either having a second case or buying a dual system case 
> which cost more than 500$$, those guys...
> Spending much money on a raid card also seem like spending money for 
> nothing too as it seems i'll have better performances with hba card + 
> zfs that using a raid card. (did some research meanwhile)

It's possible, but I don't think that's necessarily true.  ZFS' features 
come at a performance cost, in general.