Date: Mon, 21 Dec 2009 13:20:53 +0200 From: Daniel Braniss <danny@cs.huji.ac.il> To: Miroslav Lachman <000.fbsd@quip.cz> Cc: freebsd-scsi@freebsd.org Subject: Re: iSCSI initiator and Dell PowerVault MD3000i Message-ID: <E1NMgJp-000587-VZ@kabab.cs.huji.ac.il>
next in thread | raw e-mail | index | archive | help
> Daniel Braniss wrote: > > > >> So instead of iSCSI connected storage with multipath failover, I got > >> singlepath storage causing system freeze in case of network disconnection :( > > > > well, if you unplug the net, or reboot the target, it will recover. > > it's when you down/up the network when problems occur, and I'm > > looking into it. I took a machine, with 2 nics, connected to 2 vlans, A is the default, B is on the same vlan as my target iscsi server. if I unplug or do an 'ifconfig netB down', the iscsi_initiator will recover - after about 1 minute - reconnecting to the target via netA > Just the note to my tests with multipathing. I asked about MD3000i one > friend who is aware of DELL arrays and he told me that it is > 'active/passive' / 'dual active' type of array and Virtual Disks (LUNs) > are always accessible only by one controller. In case of failure of > currently active controller path, the driver must send some command to > the other controller to take ownership of the LUN to this controller. > > I searched the net for some more information and it seems that it is > handled by RDAC on Linux > (http://fxr.watson.org/fxr/source/drivers/md/dm-mpath-rdac.c?v=linux-2.6) but > we don't have it in FreeBSD? > http://lists.freebsd.org/pipermail/freebsd-scsi/2009-December/004045.html > > Do you have some knowledge about this? Is it something that can be done > in iSCSI or is it something for another part / layer in the FreeBSD? > Let me see if I can untangle all these acronyms :-) iSCSI is scsi over ip, it's 'usually' presented some 'scsi device', tape, disk, via some target. It's the target that controls the real hardware, so a hardware error at the raid controller level cannot be handled by the initiator (so no RDAC), specially when the target provides a virtual disk (which is about 100% true for all the targets I have encountered so far). A RAID controller is not a SCSI device, and so it can't be controlled by the iSCSI initiator. Multipath, in iSCSI it means more than one network path to the same target/lun, the current iscsi_initiator does not handle this, but since istg handles this, I'm looking into it. it would be helpful if you can describe what you are trying to accomplish. danny
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?E1NMgJp-000587-VZ>