iSCSI initiator and Dell PowerVault MD3000i

[Miroslav Lachman]

Daniel Braniss wrote:
>> Daniel Braniss wrote:
>>
>> [...]
[...]
>> I think there is in-band management commands (management over iSCSI
>> interface of the MD3000i) used to move virtual disks between controllers
>> driven by connected host / driver in OS.
> I tend to believe that this is out-of-band, ie, http. when you connect to the
> target, you get only virtual disks, ie, da0, da3, etc. this are scsi disks.
> if there was some scsi-raid, then it should appear as some other device,
> like tape robots, they have st0 for the tape, and ch0 for the 'robot'.
>>
>> I am not too experienced with iSCSI / SCSI, so please correct me if I am
>> doing something wrong or I have wrong expectations.
>>
>> Miroslav Lachman
>
> if you are not planning to use the network, ie, you mentioned cross cable,
> and no switches, then you can get the MD3000 (notice no i :-),
> and you can then connect it using SAS cable(/s) to a raid controller.
> We do that here, have a dell PowerEdge 2950, running 7.2 (and soon 8.0)
> conected to a MD3000. btw, SAS is several times faster than iSCSI. We run
> ZFS on it and provide NAS services via NFS to several hosts.

This is just a testing setup, there are plans to use it as SAN with 
other systems (mainly ESX virtualized Windows for other projects, but 
ESX and Windows is not part of my work ;])

My current setup:
Direct-Attached Servers, Dual-Path Data, Dual Controllers (Duplex)
http://support.dell.com/support/edocs/systems/md3000i/en/2ndGen/IG/HTML/hardware.htm#wp1008180

Future planned setup:
SAN-Configured Servers, Dual-Path Data, Dual Controllers (Duplex)
http://support.dell.com/support/edocs/systems/md3000i/en/2ndGen/IG/HTML/hardware.htm#wp1011011

> If you go the network/iSCSI route, you can share virtual disks
> aming hosts - as long as they are readlony, or move them around r/w between
> hosts.
>
> anyways, all this multipath stuff is tickling my curiosity, stay tuned :-)

I found that there is something called "Controller-based Auto Virtual 
Disk Transfer (AVT)" but I can't find this feature in MD Storage Manager 
and I can't find any useful detailed info for this feature. I only tried 
to disable one controller and then all LUNs were migrated to active 
controller. But it does not happen when network to controller is down. 
So still there must be something on the host to send some command to 
MD3000i to move LUNs to other controller in case of network failure.

If you (or somebody else) are interested in "how it works with other 
OS", there are some links:

Debian, Dell MD3000i, dm_multipath and path checking
http://blog.loftninjas.org/2008/06/13/debian-dell-md3000i-dm_multipath-and-path-checking/

The MD3000i uses RDAC to impliment failover
http://www.performancemagic.com/Dell1950_MD3000i_Xen_Debian_iSCSI_RDAC/Multipathing.html

MPIO to PowerVault MD3000i with Microsoft iSCSI Initiator
http://www.delltechcenter.com/page/MPIO+to+PowerVault+MD3000i+with+Microsoft+iSCSI+Initiator

Miroslav Lachman

PS: let me know if you want something more about MD3000i, screenshots 
from management SW, manuals, linux driver sources etc.