InfiniBand Storage

Question

I'm contemplating the next restructuring of my medium-size storage. It's currently about 30TB, shared via AoE. My main options are:

1. Keep as is. It can still grow for a while.
2. Go iSCSI. currently it's a little slower, but there are more options
3. Fibre Channel.
4. InfiniBand.

Personally, I like the price/performance of InfiniBand host adapters, and most of the offerings at Supermicro (my preferred hardware brand) have IB as an option.

Linux has had IPoIB drivers for a while; but I don't know if there's a well-known usage for storage. Most comments about iSCSI over IB talk about iSER, and how it's not supported by some iSCSI stacks.

So, does anybody have some pointers about how to use IB for shared storage for Linux servers? Is there any initiator/target project out there? Can I simply use iSCSI over IPoIB?

Answer 1

I've just had to deal with an IB SAN using Mellanox NICs. Works out of the box on RHEL

Answer 2

Do you need IB's latency benefits or are you just looking for some form of combination of networking and storage? if the former then you have no choice, IB is great but can be hard to manage, FC works great and is nice and fast but feels a bit 'old hat' sometimes, iSCSI can be a great solution if you consider all the implications. If I were you I'd go for FC storage over FCoE via Cisco Nexus LAN switches and a converged network adapter.

Answer 3

Although it is possible to run iSCSI over InfiniBand via IPoIB, the iSER and SRP protocols yield significantly better performance on an InfiniBand network. An iSER implementation for Linux is available via the tgt project and an SRP implementation for Linux is available via the SCST project. Regarding Windows support: at this time there is no iSER initiator driver available for Windows. But an SRP initiator driver for Windows is available in the winOFED software package (see also the openfabrics.org website).

Answer 4

What about 10gb ethernet? The more exotic the interface, the harder time you're going to have finding drivers and chasing away bugs, and the more expensive everything is going to be.

Okay -- here is a cheap rundown given that everything's all within cx4 cable distances (15 meters):

(I'm using us dollars and list prices found on web pages. I'm assuming the vendor prices are USD are as well)

• Switch: $5222
• 10gig card with cx4 interface: $495 x12
• cx4 cables: $82 x6 + $165 x6
• Grand total: $12,700

Is infiniband that much cheaper?

(please note -- I've never actually used any of this gear, I'm only going by whatever pops up on google after 30 seconds of googling. I'm certainly not endorsing it or making recommendations that it will do anything good or bad)

Answer 5

NFS over RDMA works GREAT in Fedora linux

It's very easy to set up. Install the right rpms and tweak a couple of files. Just google to find instructions.

I used Mellanox MT25208 PCIe-x8 infiniband cards, flashed to the latest firmware. Total cost for two cards and a 15 M cable: $150. Who cares about "market adoption" at that price.

Smokin' bandwidth, well over 400 MBytes/sec, with very little CPU usage on client or server. The bottleneck is the RAID controller.

As a bonus, X over IPOIB is also smokin', you'd swear the app is local.

Answer 6

I approached the same problem by using 10-Gigabit iSCSI with a dedicated 6-port switch (HP 6400cl-6XG - $2200) and Intel dual-port CX4 NICs (Intel EXPX9502CX4 - $650). The cost per server came down to the NIC and a $100 CX4 cable. In this case, very little was needed to get drivers, etc. to work in a mixed Linux, Windows and OpenSolaris environment.

Answer 7

The difficulty with IB when building a SAN is to manage the srp target. There are very few pre-built solutions available and most are expensive. If products like Open-E introduced native IB support into their software (specifically srp) you would have an easy hardware solution. The client side is very simple to set up on RHEL and it works perfectly. We have a test system up and running now which is performing at 600MB/s consistently and under high load. The performance is amazing and the large amount of available bandwidth gives you great peace of mind and flexibility. Yes you are still limited to the speed of your array, but with IB you can connect multiple arrays without losing performance. Use one for backups, one for main storage etc etc and use them simultaneously without any loss of performance. In my experience, as a pure RDMA storage network, without IP, there is nothing that can beat IB and if you shop around, you can set something up for a very reasonable price. If someone was to introduce some storage appliance software similar to Open-E with full SCST SRP target support it would open up the mainstream market to IB and I for one would be very happy.

Answer 8

I have not implemented an IB storage solution myself, but the main problem as I understand it is that the host drivers are not in wide use in your average environment. They are in wider use in the Windows world than in the Linux world. Where they are in use in the linux world, it's usually in "packaged" infiniband hardware appliances or supercomputing applications with tuned/customized drivers.

10g ethernet or 10g fiber is in much broader use.