On Sun, Feb 13, 2011 at 9:44 PM, Robert Heller <heller at deepsoft.com> wrote: > At Sun, 13 Feb 2011 11:00:39 -0800 CentOS mailing list <centos at centos.org> wrote: > >> >> On 02/13/11 10:53 AM, Rudi Ahlers wrote: >> > Does any one know how to, if at all possible currently, to export a >> > block device via eSATA? i.e. how do I do something like iSCSI, but >> > over eSATA? >> > >> > I have a cheat ($15 probably?) media player at home (Egreat EG-M31B >> > Network Media Tank - awesome little machine) that runs some flavor of >> > Debian and can be connected to any PC via eSATA as an external HDD's. >> > i.e. it exports the built-in HDD as a block device to the host (My >> > laptop or PC). >> > >> > Now, the question is, how can I do this on Linux? >> > Would I need a different eSATA card than the on-board eSATA port on >> > most motherboards? Or would the on-board one work? >> >> I suspect your media tank is doing something electrical, like idling its >> processor, and re-routing the sata port directly to the internal storage >> device, when its in this mode. I'm unaware of any SATA target drivers >> (as opposed to the normal initiator drivers in libata etc) > > More likely, it is running some custom software the connects to the > exposed port (which is probably not a typical PC SATA port -- it would > be wired like a Hard Drive's SATA connector (opposite gender, opposite > signal directions, etc.). The custom software presents itself on this > port like it was a hard drive and implements some sort of logical hard > drive based on the actual internal hard drive -- not really much > different from a USB connected mp3 player or camera -- the USB > connected mp3 players / camera are just using a different physical > interface (USB), but the logic is the same. Again, the USB port on > these devices is 'wired' the opposite from the USB port on a normal PC > and the logic behind it is also opposite (you cannot really connect a > USB port of one PC to the USB port of another -- there is no such thing > as a USB 'cross over' (Ethernet) or null-modem (RS232) cable in the USB > (or firewire) world). The processor in the little box is implementing > much that same sort of processing that goes on inside the micro > processor on the controller board of a hard drive -- modern hard drive > controller boards are really a full fledged little computer running a > very special program that implements the drive end of the mass storage > interface (SCSI, SATA, PATA, etc.). The media tank is just taking this > to a different level. > >> >> >> Sure, I understand what you're saying, but the question is: If they can do it with a cheap device like this, then surely one should be able todo it with a normal / server motherboard? Obviously they won't tell us their secrets, so I need to dig around to see how todo it myself. This particular device has a eSATA slave + eSATA Master mode. i.e. I can connect another device to this one and they both work together, and then when I connect the first one to my PC, I have 2 HDD's - i.e. a cheap JBOD implementation. I'm trying to see if I can setup a Linux JBOD on a server chassis with say 16 HDD's or something, and then connect it to another server via eSATA - i.e. building a cheap scalable SAN. P.S. You actually do get USB cross-over cables: http://en.kioskea.net/faq/342-connecting-two-computers-with-a-usb-cable - they work quite well. They're not as fast a gigabit but works very well for older PC's without LAN. -- Kind Regards Rudi Ahlers SoftDux Website: http://www.SoftDux.com Technical Blog: http://Blog.SoftDux.com Office: 087 805 9573 Cell: 082 554 7532