Why hardware RAID controller is not recommended for unRAID?

[MarKol4]

Greetings!

 

I have heard many voices saying that a hardware controller (e.g. PERC) having drives configured as a RAID volume (e.g. 6) would not work with unRAID?

Can anyone explain why is that? Should unRAID care what type of block device it gets to build its own array?

 

For example I was thinking about the following config:

=> 2x hardware controller

=> 2x raid 6 volume built on each of hardware controllers

=> unRAID array built of raid 6 volumes provided by the hardware controllers

=> no parity or redundancy configured for the unRAID array

 

Due to the fact of having hardware controllers with cache and BBU/FBWC I would expect:

=> better write and read performance in comparison to pure unRAID array with redundancy

=> ability to survive 2 disk failures in each of the raid 6 volumes (4 disks in total)

=> ability to trade performance vs reliability by adding extra redundancy in unRAID (parity drive)

 

What I'm missing here? Why the above config is no go for unRAID? It cannot be done with unRAID or it is just not recommended? What are the main reasons?

 

Thanks.

 

[Vr2Io]

3 hours ago, MarKol4 said:

What I'm missing here? Why the above config is no go for unRAID?

You can use above setup with Unraid, but if you ask those question, it really don't understand why Unraid user use it rather then "hardware controllers with cache and BBU/FBWC".

 

Every solution have its cons/pros, no one are perfect or robust, I highlight why I like Unraid more then others FYR

- Power saving, most disks could be spindown.

- File pooling instead block level, expand storage just add disks, no re-balance / rebuild need in general. ( exclude if you add by volumes volumes volumes ..... )

- Easy exchange disk between different system ( cross different disk controller ), straightforward to manage disks and its health.

- Swap age disks for other purpose down to one by one.

 

 

What main pain for HW RAID

- It work like a blackbox, Unraid can't control or show the health status.

- Extra layer - disk controller driven

- Disk in group/set instead standalone.

- BBU ( battery will dead ).

 

All solution have draw back, depends on which you like. If use Unraid over HW RAID, it seems you like file pooling rather then LVM.