Dell R710 with PERC H310. GPT issues and hardware raid or ZFS?

[Jeremy Chadwick]

On Sat, Jun 22, 2013 at 07:19:28PM +0100, John wrote:
> Hello, thank you for your reply.
> 
> On 22/06/2013 18:48, Steven Hartland wrote:
> > I see you have an dell + mfi controller, there was an important FW update
> > released a week or so back do ensure you have that installed or you'll
> > suffer from nasty IO stalls.
> 
> Thats... thats what I was seeing!!! I was running a svn update for ports
> and svn just sat there like a piece of cheese in a state of wdrain
> according to top.
> 
> OK so firstly I need to update the controller. After some googling I
> found this site https://calomel.org/zfs_raid_speed_capacity.html where
> they "raid0" each disk to take advantage of the controller, but it seems
> (so far) with my controller that once hardware raid is enabled it can't
> be disabled. It does not allow the opportunity to make one raid0 disk
> from one disk and then go to another disk to do the same. Maybe I should
> do it with the first one  then let zfs do the remaining three.

1. I would recommend you avoid use of the controller entirely.  Get
yourself a different controller that doesn't do RAID and use that.  If
you can disable the on-board controller in the BIOS, and pick yourself
up a Supermicro AOC-USAS2-L8e HBA (around US$140) and use that
(or even a siis(4) controller (around US$30)), you'd be better off.

http://www.supermicro.com/products/accessories/addon/AOC-USAS2-L8i.cfm?TYP=E

This uses the mps(4) driver.

I'm intentionally keeping this terse rather than going into the
different HBA types (ex. the 2108 uses mfi(4) (avoid please), and there
are other models which do RAID but some which can have RAID disabled by
using a different "version" of firmware (have to ask Technical Support
for it, etc.).

2. The "make each disk a RAID 0 volume" has caveats which the author of
that article does not disclose.  One of the biggest is if you plan on
using SSDs with the controller -- you won't be able to get TRIM/UNMAP
support (via SCSI commands 0x85 (PASS-THROUGH-16) or 0xa1
(PASS-THROUGH-12) doing that, which will hurt you **big time**.

It probably varies per controller, but it's proof that using a non-RAID
controller is always the way to go with ZFS.  Proof of the "RAID 0
volume per disk" crap:

http://lists.freebsd.org/pipermail/freebsd-stable/2013-June/073680.html

-- 
| Jeremy Chadwick                                   jdc at koitsu.org |
| UNIX Systems Administrator                http://jdc.koitsu.org/ |
| Making life hard for others since 1977.             PGP 4BD6C0CB |