On Jan 21, 2011, at 6:41 PM, Edward Morbius <dredmorbius@gmail.com> wrote:

We've been wrestling with this for ... rather longer than I'd care to admit.

Host / initiator systems are a number of real and virtualized CentOS 5.5 boxes. Storage arrays / targets are Dell MD3220i storage arrays.

...

You need the RDAC kernel module installed, this handles asymmetric multipathing to these devices.

You can get this from Dell's site.

Once this is installed you need to setup dm-multipath, look for multipathd.conf in /etc, get the product id and vendor id from dmesg after making an initial connection via open-iscsi and use that in the mutipath config. Your going to need to use path utility 'rdac' in the config instead of tur.

Google is your friend here.

We've got *an* rdac module installed. Any way of telling whether or not this is Dell's? RPM says these are from kernel-2.6.18-194.17.1.el5.src.rpm.

$ lsmod | grep rdac
scsi_dh_rdac           43977 0
scsi_dh                42177 2 scsi_dh_rdac,dm_multipath
scsi_mod              196953 14 scsi_dh_rdac,be2iscsi,ib_iser,iscsi_tcp,bnx2i,cxgb3i,libiscsi2,scsi_transport_iscsi2,scsi_dh,sr_mod,sg,libata,megaraid_sas,sd_mod

$ rpm -qif $(locate rdac.ko)
Name        : kernel                       Relocations: (not relocatable)
Version     : 2.6.18                            Vendor: CentOS
Release     : 194.17.1.el5                  Build Date: Wed 29 Sep 2010 11:57:11 AM PDT
Install Date: Thu 14 Oct 2010 02:17:14 PM PDT      Build Host: builder10.centos.org
Group       : System Environment/Kernel     Source RPM: kernel-2.6.18-194.17.1.el5.src.rpm
Size        : 96488290                         License: GPLv2
Signature   : DSA/SHA1, Thu 30 Sep 2010 08:35:49 AM PDT, Key ID a8a447dce8562897
URL         : http://www.kernel.org/
Summary     : The Linux kernel (the core of the Linux operating system)
Description :
The kernel package contains the Linux kernel (vmlinuz), the core of any
Linux operating system. The kernel handles the basic functions
of the operating system: memory allocation, process allocation, device
input and output, etc.
Name        : kernel                       Relocations: (not relocatable)
Version     : 2.6.18                            Vendor: CentOS
Release     : 194.17.1.el5                  Build Date: Wed 29 Sep 2010 11:57:11 AM PDT
Install Date: Thu 14 Oct 2010 02:17:14 PM PDT      Build Host: builder10.centos.org
Group       : System Environment/Kernel     Source RPM: kernel-2.6.18-194.17.1.el5.src.rpm
Size        : 96488290                         License: GPLv2
Signature   : DSA/SHA1, Thu 30 Sep 2010 08:35:49 AM PDT, Key ID a8a447dce8562897
URL         : http://www.kernel.org/
Summary     : The Linux kernel (the core of the Linux operating system)
Description :
The kernel package contains the Linux kernel (vmlinuz), the core of any
Linux operating system. The kernel handles the basic functions
of the operating system: memory allocation, process allocation, device
input and output, etc.

There's also a rebuild of 'sg', with a source tree in /usr/src/sg-3.5.34dell

Diffing sources:

$ diff sg.c sg.c_rhel5
22c22
< #define SG_VERSION_STR "3.5.34dell"
---
> #define SG_VERSION_STR "3.5.34"
1879c1879
<         sg->length = (ret_sz > num) ? num : ret_sz;
---
>         sg->length = ret_sz;

I'll also note that Dell isn't playing nice with its package installs -- some stuff is under /opt/dell, some is installed via RPM, some appears to be tossed arbitrarily onto the system:

$ rpm -qif /lib/modules/2.6.18-194.17.1.el5/extra/sg.ko
file /lib/modules/2.6.18-194.17.1.el5/extra/sg.ko is not owned by any package

Bad Dell. No donut.

-Ross

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