On Sun, 26 Apr 2015 04:30:31 PM Craig Sanders wrote:
Last time I tried this with a HP server there was no way to run drives without having the RAID header. The RAID header tells the RAID controller to treat the disk as a JBOD, but it makes the disk slightly smaller and at a slight offset.
i.e. it can't be done without wiping the original drives. it might be possible to shrink the filesystem and partitions on the orig drives and use gparted to move the partition(s) to make room for the raid offset....but that's a lot of stuffing around - would probably be much less hassle to backup, repartition with the HW raid, and restore.
Yes.
stupid crap like this is one of the reasons why HW raid cards should be avoided. this is an anti-feature that serves onlY HP by locking in customers to their products.
I think that HP RAID supports a purported industry standard for such things, so it's not just them. Also if you have the RAID metadata at the front of the disk then a RAID volume can't be accidentally mounted as non-RAID. In the early days of Linux Software RAID it was a feature that you could mount half of a RAID-1 array as a non-RAID, but that had serious potential for data loss if you made a mistake. Now Linux Software RAID usually defaults to the version 1.2 format which has the metadata at the start. So your criticism of HP RAID can be applied to Linux Software RAID.
Unless you are going to use ZFS or BTRFS then the HP hardware RAID is a better option.
i disagree with the last part of that. the only time hardware raid is even a reasonable option is when you want to use RAID5/6 *AND* you have a support contract with the HW vendor *AND* can afford to have a second identical raid card sitting idle.
If you buy a HP server to run something important that needs little down-time then you probably have just that. If your HP server doesn't need such support guarantees then you can probably deal with a delay in getting a new RAID card.
that still doesn't make hardware raid a better or even good solution, just a tolerable one.
for raid-1 or 10, software raid beats the hell out of HW raid,
For RAID-5 and RAID-6 a HP hardware RAID with battery backed write-back cache vastly outperforms any pure software RAID implementation.
and ZFS mirrored pairs adds error-checking and correction of data as well as snapshotting and many other useful features.
for RAID-5 or RAID-6 linux software raid is better, and ZFS RAID-Z is far superior for the same reasons that ZFS mirroring is superior to RAID-1.
I agree that ZFS features are good and I've run a HP server with it's RAID configured as a JBOD for ZFS. But I've also run HP RAID-6 and found it to be dramatically better than Linux Software RAID. -- My Main Blog http://etbe.coker.com.au/ My Documents Blog http://doc.coker.com.au/