MD1000 connected with two SAS cables in unified mode

Nick_Parrott at Dell.com Nick_Parrott at Dell.com
Fri Sep 12 04:31:48 CDT 2008


Hi Jeff,

>From what I understand of the MD1000 EMMs, there is failover, but only
for the management communications to the chassis, there is no data path
failover.. so losing the active EMM/connection will result in the PERC
needing to re-init (host reboot). This limitation is determined by the
PERC..

Agreed, not much use in monitoring the chassis if the data path is
unavailable, but useful to understand the failure sometimes. I've
checked every Dell doc I can see here, and there isn't a single image or
mention of 2 cables from PERC to Unified MD1000, however I've had a good
few customers manage this fine, with an MPIO driver to take care of the
multiple LUNs.

Maybe anyone else who's done this before can comment on it's success..

-----Original Message-----
From: linux-poweredge-bounces at dell.com
[mailto:linux-poweredge-bounces at dell.com] On Behalf Of
Patrick_Boyd at dell.com
Sent: 11 September 2008 22:20
To: jewing at aconex.com; linux-poweredge-Lists
Subject: RE: MD1000 connected with two SAS cables in unified mode

This does not provide any fail over. Assuming that you have this
connected to a PERC, this can result in the PERC doing very odd things.

-----Original Message-----
From: linux-poweredge-bounces at dell.com
[mailto:linux-poweredge-bounces at dell.com] On Behalf Of Jeff Ewing
Sent: Thursday, September 11, 2008 3:53 PM
To: linux-poweredge-Lists
Subject: Re: MD1000 connected with two SAS cables in unified mode



> This configuration is a problem and results in many times in seeing
all
> luns 2 times.

That is what is confusing me. I expected to see two paths in
/proc/scsi/scsi
and two sets of devices in OpenManage but I dont.  I was wondering if
this 
provided some kind of fail over facility. If not, I will get the second
cable
removed by our Dell service technician when we add more PERC cards and
arrays
next week.




On Thu, Sep 11, 2008 at 01:06:31PM +0100, Patrick_Fischer at Dell.com
wrote:
> Two cables are only supported in split mode in all other cases only
one.
> It has its cause that it is not in the manual because it doesn't make
> sence anyway.
> 
> -----Original Message-----
> From: linux-poweredge-bounces at dell.com
> Sent: Thursday, September 11, 2008 1:57 PM
> To: linux-poweredge-Lists
> Subject: MD1000 connected with two SAS cables in unified mode
> 
> The MD1000 array on my Redhat server was connected with two SAS cables
> from the dual port PERC 5 card to each EMM on the MD1000 array.
> It operates in unified mode.
> 
> This configuration is not described in the
> MD1000 Hardware owners manual.
> 
> Could this configuration cause problems?
> 
> Does this configuration provide any benefit?
> 
> 
> Jeff
> 

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