Re: btrfs subvolume as an iSCSI target?

On 03/12/2014 04:23 PM, Dan Mossor issued this missive: > I've been combing the web for a couple days, and most hits I'm finding > regarding using a btrfs subvolume as an iSCSI target are posts from the > 2009/2010 timeframe stating that that functionality is broken. > > I'm working on a couple projects here, and one of those involves the > research into iSCSI targets and initiators, and the testing thereof. I > have an F20 system with a 1.3TB btrfs master subvolume (across three > dissimilar devices), and want to create a subvolume within that to serve > as an iSCSI target. > > The traditional methods, specifically those mentioned in the Fedora Wiki > and the tgtadm man pages, place the emphasis on using devices (/dev/sdx) > or files (dd if=/dev/zero of=/array/target1 bs=1k count=1). I realize > that using the file is probably the easiest thing to do in this > instance, but that's not the point of my project - I am intentionally > trying to designate the btrfs subvolume as the target. > > The issue I believe that is going to stop me is that tgtadm expects a > block device as the target, and btrfs does not provide that. Is there a > workaround, other than using a file in the subvolume as the target? Is > there work in progress to enable this feature, either in the > scsi-target-utils package or within the btrfs framework? iSCSI stands for "internet SCSI", a way to share raw devices over normal network mechanisms rather than having to have a storage farm (e.g. fiberchannel switches or SAS concentrators and a ton of cables). As far as I know, the functionality you want will never be available. iSCSI is intended to share raw devices, not subdirectories (that's what things like NFS and CIFS are for).