LSI - MR-Fusion controller driver <mrsas> patch and man page

[Borja Marcos]

On Mar 24, 2014, at 6:45 PM, Doug Ambrisko wrote:

> On Mon, Mar 24, 2014 at 09:03:43AM +0100, Borja Marcos wrote:
> | 
> | On Mar 21, 2014, at 5:09 PM, Doug Ambrisko wrote:
> | 
> | > Do you have a simple test case for that?  There were issues in the SCSI
> | > command translation which should have been fixed via switching it to use
> | > the CAM translation code.  Can you try it via a RAID volume of one disk?
> | 
> | Yes, I tried all those possibilities. "syspd" devices, passthrough 
> | (same result, corrruption) and when creating single-disk RAID0 volumes 
> | it worked, no corruption.
> 
> Okay, so you don't have and simple test case to show this.  What are
> you currently doing?  I would think the syspd and the single disk RAID0
> should be very similar.  I'll take a look at that.

Yes, sorry for not being so explicit.

The server  I tried has a backplane, with 23 disks fitted. At first  I assumed it would work, so
I just created a raidz2 vdev  and begun running benchmarks. That's where I noticed  that it was
corrupting data badly.

The disks were set as "JBOD" with the Invader's built-in configuration tool and visible as mfisyspd drives.

So I reduced it to using a single disk. Choosing one of them at random, I did a newfs. Mounted, and executed
bonnie++. I got a panic after  some time. To avoid the inconvenience of panics, I moved to ZFS (single disk vdev) 
so that I could still detect corruption.

The tests I did were:

- Disk in JBOD/syspd mode, accessed through /dev/mfisyspd -> corruption
- Disk in JBOD/syspd mode, passthrough enabled, accessed as /dev/daX -> corruption
- 1 disk RAID0 volume, accessed as /dev/mfid0 -> NO corruption

And I understand that syspd and RAID0 should be really different. I understand that it's a shallow layer
doing little more than passing through commands? I should read the driver thoroughly it seems... Pity there
are no available documents.

> | Just in case I tried with SSDs (Samsung EVO  840 and OCZ Vertex 4) and 
> | Seagate SAS disks.
> 
> So it seems generic.  Size of disk might be useful.


The Samsung are 1 TB, the OCZ are the 512 MB ones, and the Seagates are 146 GB. 
The SSDs (Samsung and OCZ) are SATA disks, the Seagate is SAS. The Seagate was corrupted as well in the
same test cases, so it doesn't seem to be linked to SATA-on-SAS or to TRIM. TRIM, anyway, doesn't work
on "mfisyspd" devices, which is a problem if you want to run ZFS on SSD disks.

> | Actually I think that converting passthrough disks to "mfisyspd" or an
> | equivalent is a bad idea, unless, of course, there's a compelling reason
> | I don't realize. For instance, if you are using SSDs you need access to
> | the TRIM command.
> | 
> | So, if I can vote, I vote with arms and legs for "da" devices in case it's
> | a passthough.
> 
> Nothing is planned to be removed from mfi.  However, LSI would like mrsas
> to be used on newer cards.  We've let people LSI know that people use
> the pass through mode and having the logical volumes come up as /dev/daX
> and pass through would be confusing.  Granted mrsas doesn't support pass
> through so that isn't a problem.

Pass through is a critical feature when you are running ZFS. I think it's a real problem
if the new driver (the only one that will support newer cards, I guess) won't support
pass-through. 

And of course I know that you can just buy making sure that you get HBAs instead of
RAID cards, but  so many manufacturers bundle those RAID controllers in fixed  configurations
that it wouldn't be practical.

The ideal solution would be to have logical volumes come up as /dev/mfid, /dev/mrsas, /dev/mfisyspd
or whatever, and passthrough devices as real passthrough devices like /dev/da. That would avoid
confusion.

So, please, LSI, consider it. It would really add to the versatility of your cards and there's nothing
to lose.

> | It's not a pressing need, I installed a LSI2008 card and I connected the 
> | SAS backplane to it, so for now the Invader
> | is a non-problem, but if it will help to run some tests with the mps 
> | driver I can certainly do it.
> 
> The mps driver is a different thing, mrsas is LSI's replacement for mfi
> with newer cards.  So if you could try syspd and single RAID 0 test
> with mrsas that would be great to see if that shows the same pattern
> of syspd failing with mfi and passing with single RAID 0.  Again,
> the logical volumes will show up as /dev/da* with no pass through
> devices.  If I can reproduce the problem then I can look into here
> or others might be able to find the solution.

I'll try, thanks :)





Borja.