by September 10, 2010 0 comments



In most data centers today you’ll still find Ethernet as the de facto
interconnect fabric for servers and storage. Familiarity could be one reason why
architects settle for this fabric; other reason could be that the
next-generation fabrics increase the cost. Though Fibre Channel has seen
increased adoption in storage area network (SAN) environments, the adoption of
10-Gig Ethernet is still to become mainstream. Apart from these two interconnect
technologies; there is InfiniBand which is gathering increased interests amongst
organizations working in high performance computing environments because of its
potential to deliver increased speeds with low latency.

Enterprise data centers host business critical applications like ERP or CRM,
which has resulted in increase of data volumes and also demand for reliability.
This has led to formation of clusters which operate parallel to serve an
application. To maintain data transfer speeds between cluster servers a reliable
interface is needed, and Inifiniband serves that well. The use of InfiniBand in
SAN vouches itself as an ideal usage in datacenters. Besides being used in HPC
environments, organizations that have used InfiniBand would already know the
benefits of it.

This time at our labs we had received Tyrone Opslag FS2, a unified storage
solution that can support 10 Gig Ethernet, Fibre Channel and InfiniBand as host
interfaces. This gave us the opportunity to benchmark the performances of these
three interconnect interfaces. Before delving into benchmarking, let’s first see
what InfiniBand is and where it is applicable.

Benefits of InfiniBand
InfiniBand is a fabric communication link that is used in enterprise data
centers and high performance computing. Like other modern interconnects, say
SATA or Fibre Channel; Inifiniband too offers a point-to-point bi-directional
serial link for connection of processors with high speed peripherals like disks.
It features high throughput, low latency, and is designed to be scalable. The
data transmitted with Inifiniband is in packets form, and this packet delivery
is handled in the hardware, not in the software. By use of credit based
flow-control mechanisms and monitoring of bandwidth, InfiniBand delivers packets
between sending and receiving nodes in a lossless way.

If as an interconnect medium we compare InfiniBand with Ethernet, the
difference is that InfiniBand is focused towards providing high reliability
connection over a short distance. In contrast Ethernet with TCP/IP is intended
towards undefined distances over any medium of connection. Though TCP/IP
provides robustness to work under any condition, and this robustness adds to the
overhead. With InfiniBand, overhead is minimal as it optimizes the data stack to
allow for Remote Direct Memory Access (RDMA). RDMA simply is the direct memory
access of one computer into that of another without involving the server’s
operating system for read/write procedures. This results in delivering very high
throughput, low latency interconnect, which is particularly essential to be used
in parallel compute cluster environments.

Thus, InfiniBand architecture simplifies the communication between the
servers and SANs in a datacenter, and also allows the scope of being scalable
while supporting quality of service and failover.

Benchmarking Setup
We used Tyrone Opslag FS2 as a SAN (Block level sharing) connected to a server
having specifications as 4x Intel Xeon quad-core processors, 32GB RAM, Windows
2008 R2. As interconnect interfaces we used InfiniBand, FC and 10Gig Ethernet
one at a time to see the throughput measured using IOMeter.

For the IOMeter tests, we used the block size of 512KB as standard and used
100% sequential read and 100% sequential write as tests to measure the
throughput of the interconnect medium. As pre-requisite we installed the
necessary drivers for each of the network interface onto the server. Also on the
SAN we configured a block target of volume 500GB which we had used as central
storage for the server with the benchmark. We connected the SAN over local
network too, so as to connect and manage the console remotely over the web
interface.

First we connected Infiniband; we installed the Mellanox 4X DDR Infiniband
card on our main server. Connecting over LAN to the Opslag FS2 console, we have
to enable the InfiniBand by going to Advanced Setup > InfiniBand Settings on the
menu. Once enabled, we have to enable the SRP settings from the same main menu
and also assign the block disk volume of 500GB that we have created earlier to
be used for streaming over SRP. Once done, and with InfiniBand connected to the
main server, we see that a new disk has been added under the Disk Management
console. We can now initialize, format and use this disk block from the SAN as a
local drive for the server.

To measure the throughput we ran the IOMeter on the newly added drive and set
the test configurations as mentioned earlier. For sequential read we were able
to get sustained throughput of 1570 MBps. While for sequential write we got a
speed of 1092 MBps.

Similarly we setup the 4G FC and 10GigE interconnect medium and conducted the
tests. The FC setup was straightforward through the web console, but for 10GigE
you need to initialize iSCSI also, and assign its initiator and target as well
because 10GigE doesn’t support native SCSI initiation. The speed that we got for
4G Fibre Channel was 390 MBps for read and write, while for 10GigE over iSCSI we
got speed for sequential read as 590 MBps and sequential write speed was
589MBps.

The InfiniBand architecture is also cheaper to FC and 10GigE, as the prices
of each of these cards is mentioned in the box. Having such virtualization base
would also be helpful in moving towards Cloud Computing, as one can already have
scalability enabled through InfiniBand.

SAN as store for Virtual Deployments
As more and more enterprise workload is moved into the virtual environment, it
becomes a challenge for the existing fabric to meet the requirement of increased
bandwidth and low latency. Since, InfiniBand can cater to such demand. We tried
to test the performance by having a virtual machine running from the main server
while its virtual disk is located in the central SAN, connected with InfiniBand.

Tyrone Opslag FS2

This is a unified storage solution for enterprises which provides both
NAS and Block sharing from a single box. For NAS or file level sharing it
can do SMB, AFP, FTP and NFS whereas for Block level sharing it can do iSCSI,
FC and SRP (over InfiniBand). You can find more information about the
product from http://tyronesystems.com . The USP of this unified storage box
is that, organizations looking for high performance storage solution can use
any interface, as it supports all the three, InfiniBand, Fiber Channel as
well as 10 Gig Ethernet.
The management of the device is through intuitive web based GUI through
which configuration and monitoring can be achieved. It also supports all
RAID types and the 4U box which we have received can support up to 24
hot-swap SAS/SATA hard drives.

The model that we received was FS2-D4A3-24 and was priced at Rs 5,23,109
(that include 12 1TB 7200 HDDs SATA HDDs) and had following specs: 1x Intel
Xeon 2GHz quad-core processor, 8GB DDR2 RAM and 4x Gigabit Ethernet

But to make sure the performance which we get is not hindered due to the
bottleneck of the Hard disk throughput. We have been sent a box with 20x
250GB HDDs.The interconnect cards that we used for the benchmarking, and
their costs: InfiniBand 4X DDR (Rs. 29,500), 10Gig Ethernet (Rs. 31,500), &
Fibre Channel 4Gbps single port (Rs. 35,500)

One can argue on the fact that why would someone not have a local datastore
where the virtual machine hard disks resides on the Host machine’s local hard
disk. The answer to this is very simple. First is the data redundancy and
scalability which can be only achieved by a SAN at the backend, the second is
the throughput. A simple server cannot match the throughput of a SAN as a server
has its limitation of number of hard disks it can have locally. And as we all
know, with RAID, the overall throughput is directly proportional to the number
of Hard disks connected to the RAID volume.

The third and the most important reason are the functionalities like vMotion
which has become very crucial for today’s complex virtualization setup. For
doing vMotion or any equivalent live migration exercise, it’s a must to have a
shared SAN (NFS or Block) at the back end which is reachable by all the Virtual
Hosts in the network.

So, to test this out, we installed VMware ESX server on the server and
created few virtual machines on it. For all these virtual machine we did not use
the local storage of the server as a datastore but used the storage of the SAN
exported has Block volumes. The virtual machine being an instance of Windows
2008 Server R2, we ran the IOMeter test from each instance onto the target drive
which was the virtual drive residing in the SAN. Through this clustered IOMeter
test we were able to get 1530MBps of throughput for sequential read and write
tests.

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