Hardware RAID strongly discouraged

[f00ch0w]

So I've read the hardware requirements and I noticed that in brackets, on several spots, writes 'Hardware RAID Strongly discouraged'. What do they mean by that? Could someone give me an explanation please?

 

[m0nkey_]

So I've read the hardware requirements and I noticed that in brackets, on several spots, writes 'Hardware RAID Strongly discouraged'. What do they mean by that? Could someone give me an explanation please?

No hardware based RAID controllers. A RAID controller will typically present all drives to FreeNAS as a single drive, something you don't want with ZFS. ZFS works best when it has direct access to the drives.

If you're using a hardware RAID controller, you're doing it wrong.

 

[melloa]

FreeNAS uses ZFS a software "RAID". You don't need a controller for that and you can use your motherboard sata ports to build the volumes. Using the hardware controller with ZFS will create a conflicts, unless it's in IT mode.

Do a little reading on OpenZFS http://open-zfs.org/wiki/Main_Page and this resource https://forums.freenas.org/index.ph...ning-vdev-zpool-zil-and-l2arc-for-noobs.7775/

 

[Pitfrr]

It means that some extension cards propose RAID capabilities (RAID 0, 1, ...). The redundancy is managed by these extension card and the system (or the OS) doesn't know that such redundancies are in place.

In FreeNAS, the redundancy is managed by the OS and therefore the OS has to be able to access the drive directly without any unknown "filter" (in that case a hardware RAID controller for example). That's why hardware RAID is strongly discouraged with FreeNAS.

And when you need to extend the number of SATA ports you can use an extension card but this card needs to allow direct access to the drive (so you might need to flash its firmware to achieve that).

 

[wblock]

Thread subject changed to the actual question.

ZFS changes the computer into a bigger and better RAID system than a hardware RAID card can provide. Using hardware RAID in addition not only does not make things better, it makes things worse with extra unnecessary hardware and software layers between ZFS and the drives.

 

[f00ch0w]

Thanks, this solved my question!

 

[JohnnyFreeNAS]

I understand the pro/con for hardware raid vs zfs. I have a hardware raid controller with cache on it and an external tower to house disks. The raid controller gives me a way of cabling up the external box of disks. my question is can i use the raid controller to take advantage of the cache and the cabling to the external box without using its raid capabilities or will it still interfere with the zfs file system?

 

[rogerh]

I understand the pro/con for hardware raid vs zfs. I have a hardware raid controller with cache on it and an external tower to house disks. The raid controller gives me a way of cabling up the external box of disks. my question is can i use the raid controller to take advantage of the cache and the cabling to the external box without using its raid capabilities or will it still interfere with the zfs file system?

Depends what controller exactly it is. It may be possible to flash the firmware to make it behave as a transparent drive controller. What model is it?

 

[Ericloewe]

take advantage of the cache

That's exactly what you don't want.

gives me a way of cabling up the external box of disks

Any SAS HBA can do that. No HW RAID required.

 

[melloa]

take advantage of the cache and the cabling

Don't use the cache. Take a look how ZFS works and you will understand why. Use original cables? 100% possible. Did it with Dells and doing with supermicros.

 

[JohnnyFreeNAS]

the purpose of using the controller was mainly to take advantage of an external drive box. in any case it would not work. This particular controller would only function when the drives were placed into its raid configuration. this was a problem because the disks were not presented to the FreeNAS the way i needed them to be. so i scrapped that idea