Date: Tue, 22 Dec 2009 12:54:02 +0100 From: Miroslav Lachman <000.fbsd@quip.cz> To: Daniel Braniss <danny@cs.huji.ac.il> Cc: freebsd-scsi@freebsd.org Subject: Re: iSCSI initiator and Dell PowerVault MD3000i Message-ID: <4B30B35A.3000206@quip.cz> In-Reply-To: <E1NN0EO-000Jyv-Mq@kabab.cs.huji.ac.il> References: <E1NMgJp-000587-VZ@kabab.cs.huji.ac.il> <4B2FB9B4.7030401@quip.cz> <E1NN0EO-000Jyv-Mq@kabab.cs.huji.ac.il>
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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.
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