Drobo

DroboPro Behind Switch

So, I’m now running my DroboPro connected to my Mac Mini via the FW400 port (it’s the older model w/o FW800). I’d love to be able to connect with iSCSI but the wireless is too slow/unreliable so I need to use my lone ethernet port for my LAN/Internet connection.

I have read/heard conflicting information about whether I can/should put the DroboPro on a switch. I have a Gigabit switch the I could put between my router (Airport Extreme) and the Mac Mini/DroboPro. Does anyone have any experience or tips on this setup as a viable network/DroboPro configuration? I’m streaming a lot of HD video on the network (both from my 4 HDHomerun devices to my Mac Mini and from my Mac Mini to my 2 AppleTVs) so am I just asking for trouble dropping the DroboPro onto my LAN on the same subnet (is this even possible)?

I read on the Drobo site (http://www.drobo.com/resources/iscsi.php) that it’s best to put this on a VLAN but 1) I don’t know if I have the experience for this and 2) I don’t know that my inexpensive D-Link Gigabit switch supports this.

Any help would be greatly appreciated.

Thanks,
David

i was in a similar position to you regarding the last of etherrnet ports, but i got a very very cheap usb->gigabit (yeah right) ethernet convertor, which actually works amazingly well. so the “network” connection goes through the usb adaptor (which to its credit easily holds 350+mbit/s and the drobopro occupies my sole GBE port.

Thanks for the suggestion. I’ll definitely consider it. Which model did you get (I saw a couple but want to make sure I have Mac support)? The one question I have is that I’m heavily loaded on my USB ports running a USB/DVI video adapter and an Elgato Turbo.HD video encoder among other peripherals.

I’m starting to this of this a little more now, the Belkin looks like it might be viable:

Belkin Gigabit USB 2.0 Network Adapter - USB - 1 x RJ-45 - 10/100/1000Base-T - External

Is this what you’re using?

no - i bought one and it was TERRIBLE

it wouldnt go more than half an hour on my x86 win 7 machine with bluescreening it (and giving the belkin driver as the cause!)

i ended up getting http://www.kenable.co.uk/product_info.php?products_id=1261

its fugly but its fast and stable

it actually just the latest chip, pure reference design, in a cheapo plastic case, but since its generic is means it works with the latest drivers from the chip manufacture

I have a Cisco/Linksys SLM2008. This is an inexpensive 8-port Gigabit ethernet switch that supports setting up VLANs. It has an easy to use Web Interface.

The SLM2008 lets you assign ports to VLANs and one port can belong to more than one VLAN. This is useful since the MacMini has only one ethernet port.

As an example you could configure on the switch
Ports 1 to 6 in VLAN1 for other computers, uplink to router, etc
Port 7 in VLAN1 and VLAN2 for your MacMini
Port 8 in VLAN2 for your DroboPro.
This should restrict the DroboPro to only getting traffic from the MacMini.

In my setup I use Firewire 800, however I have been thinking about testing out iSCSI from my MacMini to DroboPro. If you set something like this up I will be very interested in how it goes.

I might consider picking up one of these switches, sounds like you’ve had good luck with it. Thanks for the tips on setting up the VLANs. As I’m new to VLAN setup could you possibly provide a little more detail on setting the configuration above up on this particular switch and/or a link to a reference on how to do it?

Thanks![hr]

Unfortunately, I already ordered the Belkin (I don’t see your recommendation for sale in the US) so I might give it a shot based on positive feedback on Amazon. Though, with the VLAN info above I might order the Cisco/Linksys switch and go that route.

the chip it uses is “ASIX AXX88178 USB 2 to Gigabit Ethernet Adaptor”

i found a lot of really cheap adapter which use the AX88178 so i imagine they all work equally as well (and about half th price of the belkin at least over here)

Just an update that I’m going to give the VLAN a go. I ordered the Linksys SRW2008 and found a great tutorial on setting this up:

http://www.smallnetbuilder.com/lanwan/lanwan-howto/30071-vlan-how-to-segmenting-a-small-lan

So, I’ll probably return the Belkin adapter and hopefully get this VLAN setup later this week. Wish me luck!

In this particular model there is a VLAN page in the Web interface. By default it has just the one VLAN, number 1.
Select it and click modify and you can choose which of the 8 ports are in this VLAN.
Also from the VLAN page you can create a new VLAN (e.g. number 2) and again assign the ports you want in it.

Using VLANs for the DroboPro you only want to restrict the traffic so I suspect it should just be a matter of setting up as I posted previously.

However if you have trouble a proper VLAN type setup is used to have multiple IP ranges on your network.
e.g.
VLAN1 may have PCs in the IP range of 192.168.1.x
VLAN2 may have PCs in the IP range of 192.168.2.x
You should still be able to do this with the single ethernet port on the MacMini by creating a virtual network interface on the Mac - easily done through the System Preferences on the Mac.
But again, just to segregate out the DroboPro from the rest of your network I you probably won’t have to bother with this type of setup.

I’m not sure adding a VLAN will actually help performance.

Apologies if you all know this, I’m from a networking design/architecture background and have beta tested hardware and software networking products for a while now.

Ethernet switches, by design, do not send all traffic they receive on one port to all ports (that is what hubs do). They selectively forward traffic to ports where they know a destination to be (or to all ports, if the destination is unknown (aka the learning process)). So, if you have a DroboPro on a switch, it should only ‘see’ traffic addressed to it, broadcast and multicast traffic. Most home networks will have virtually no such traffic on them. Directed traffic is called Unicast (single destination) to complete the terms.

So, what will a VLAN add in this situation?

Well, it will mean the DroboPro will still see the traffic it needs to (as before), but misses out on the tiny quantity of other traffic. It will be ‘invisible’ to everything else not on that VLAN - which is a security enhancement. Although VLANs are not really rated a security ‘barriers’ in more than low security environments.

VLANs work by adding 4 extra bytes to each packet, containing the VLAN ID. In effect, the envelope containing your data is put into second slightly larger envelope for transport, then the outer envelope discarded and the original handed to the destination.

On any given ethernet port or cable, only one VLAN can be untagged but many other tagged VLANs can be carried. The extra tags mean anything else just ignores the packet. So, the MacMini is going to have tag traffic on the DroboPro VLAN. This requires CPU, and a slight increase in the usage on the wire (an extra 4 bytes per frame). The switch will take off the tag and forward the packet on the ‘untagged’ port the Drobo is on. Switches do this in hardware, so no problems there.

The computer (a MacMini for me) has a single ethernet interface, which means it has to carry all the traffic. The addition of the VLAN tagging on this interface seems to negate any potential benefit this may introduce - unless it is the Drobo itself which requires a ‘clean’ network to work from. Which would be a stunning bit of bad design on Drobo’s part which I seriously doubt.

I have the DroboPro connected to a MacMini, acting as a sevrer for the rest of the network. When everything was on an AirPort extreme to give a GB switch, transfers from my iMac to the DroboPro would run the ethernet at about 46MByte/sec. Since I put an HP 1810G-8 port GB switch in, these now often go up to 50 MByte/sec in my limited testing. This seems probably down to the very low latency on the HP switch over the Apple device. Just duplication of a folder on the Drobo with some large files in using the MacMini I’ve seen the network to the Drobo peak at 70MByte/sec in/out as the files are read and re-written back (this doesn’t touch the ManMini HD, so a handy quick and dirty test)

I would expect Drobo to state that the DroboPro should be connected to a dedicated port in the computer. This is the best way to ensure best performance, as no other (web browsing, e-mail etc.) traffic will ever impact the available bandwidth between the Drobo and the computer. As soon as you get into the VALN (or even multihoming) the available space for iSCSI is the ethernet speed less anything else going on at the time.

Apologies for the long post, hope it helps. I’d still be interested in any before and after tests though. If I get time, I may have a tinker and see that happens too.

Yes absolutely agree. You won’t see a performance benefit.

The major benefit is security. DroboPro just lets you configure and IP Address - you can’t assign LUNs to specific computers as you can with the DroboElite.

If you happened to have DroboDashboard installed on more than one PC on your network (perhaps because you have another Drobo) it would probably see the DroboPro even if you didn’t want that PC to - so could cause some issues.

I also recall a thread on the forums where someone was having an issue and suspected the cause was another device on the network doing something dodgy. This really should not affect a DroboPro but VLANs ensures it won’t.

Just FYI, this is from the Drobo site:

So, if I’m understanding what you guys are saying, I COULD just stick the DroboPro behind my existing switch and it should work fine until I get the new VLAN-capable switch? Seems I had talked to Drobo support once and they recommended against running behind a switch without using a VLAN or dedicated network.

Yes. It would work fine, but expect a lower performance when you add the VLANs into the equation.

I have an 8 port GB switch, no VLANs and the like. To this is connected:

MacMini
DroboPro
iMac
Sonos Music player ZP120 (+ three more zones via Sonos own WiFi mesh)
AirPort Extreme Wireless bridge ( this is connected to my Cable Modem)
ReadyNAS NVX

Via Wireless from the AirPort is a MacBook Pro, PC Laptop, 2 iPhones, WiFi Printer/Scanner

The DroboPro is shared via the MacMini to everything else.

I have no problems, performance is pretty good. Direct from the MacMini I’ve seen averages of 70 MByte/sec read and about 65 MBytes/sec write. Whilst the iMac is streaming a video from the internet and I’m screen sharing the Mini to get the stats.

If designing a high performance system, with multiple DroboPro’s or a DroboElite shared between multiple servers then it would be worth building an iSCSI LAN. Just as you would with Fibre Channel. For a single device, ideally have it on its own physical network card. If this is not an option, and you want an increased level of protection for the Drobo from the rest of your network, then perhaps look at the VLAN solution. Although, the data is just as vulnerable, being at that point behind the server it is attached to rather than just on the network. Different attack path, and probably easier to attack than the iSCSI side of things.

For ideal performance, a low latency switch which supports flow control, Jumbo frames (assuming the DroboPro actually supports them) is all you really need. I went with the HP switch, which is very low latency. The Cisco has the first two, they don’t publish the latency.

Thanks! Now, I’m torn whether I should keep the new switch with VLAN or just use my existing Dlink GB switch.

Benchmark some copies with the D-Link, pop in the Cisco and run them again (you will need several passes) - see if you get any gain from the Cisco.

What model D-Link, I may be able to dig up some specs to compare the different switches.

Thanks so much for the help and advice. I have the D-Link DGS-1016D and the new one is a Linksys SRW2008. In either case, sounds like I probably don’t need VLAN if I want optimal performance.

There isn’t much available of either unit, bar the normal specs showing ‘wire-speed’ performance.

If the D-Link does all you need it to, and you are happy with it I’d stick with it. It has 16 ports over the Linksys 8 port. If you can try the Linksys before returning it, can’t hurt to do some testing though can it?

If the D-Link turns it’s toes up, look at the small HP ProCurve’s to replace it. Lifetime warranty (I have had fans replaced after 8 years, next day swap out) too. I am biased toward the ProCurve range though having been working with them for over 10 years now.

Always go with the recommendations of Drobo Support. If you do have any problems then the first thing they may tell you to do is separate it out via VLANs as per the Knowledge Base article.

Valid point. If I have to use support and they ask me, I will just directly connect the MacMini to the DroboPro with a Cat5 (with static IP’s assigned). That will be a dedicated network for the purposes of testing and an easy way to rule external influence in or out for testing. Diagnosis of an issue by creating a more complex network seems a bit odd to me when looking to isolate an issue.

Anyone know how Drobo would take it being on a separate IP subnet and multihoming the computer? Or is the concern just other traffic which may be on the LAN?

I think I’ll have a play with the VLAN setup later in the week and do some tests, just to see the impact of a more ‘correct’ iSCSI configuration. It will be a bit of fun (!).