SSB REPORT
FC vs Ethernet
Connectivity, especially in the high-end of the storage systems market,
is undergoing a rapid transition to higher bandwidth technologies. A
number of trends are driving the need to increase effective I/O bandwidth
between clients, servers, peripherals and networks. These factors have
created a rapid increase in the transfer of data between the desktop,
servers, peripherals and networks, resulting in substantial I/O and
network bottlenecks. Some of these are as follows:
X The introduction of increasingly powerful processors require more
rapidly accessed and intelligently managed data.
X Advanced operating systems, especially advances in open systems such as
UNIX and Windows NT, allow for faster I/O and multitasking.
X The growth of data-intensive software applications, such as graphics
and video, require increases in bandwidth.
X The proliferation of client/server networks, the Internet, email and
corporate intranets all drive growth in the number of servers clients,
all communicating over the same network.
X The growth in high performance peripherals, such as high capacity hard
disk drives, scanners, CD-ROMs, digital photography and voice recognition
technologies adds to the flow of information over the network.
The existing storage connectivity standard, SCSI, has begun to fall short
of the rapidly advancing system I/O demands. Due to the inherent
limitations of the SCSI standard, a new storage connectivity standard,
Fibre Channel, has emerging to take its place. This new standard has
gained strong momentum in the past year as the heir apparent to SCSI and
the enabler of Storage Area Networks (SANs); thereby, bringing the
additional benefits of networking to the storage world.
Note: Fibre Channel is based on SCSI protocol, think of it as supped up
SCSI.
Fibre Channel Moves Data More Quickly
Fibre Channel represents the combination of connectivity and networking.
While SCSI currently moves data at 40 and 80 Megabytes per second, Fibre
Channel currently moves data at one Gigabit per second (referred to as 1
Gbps, also referred to as 100 Megabytes per second or 100 MB/sec or 100
Mbps; its all the same thing).
Another benefit of Fibre Channel is that it is bi-directional, which
means that it can send and receive data at the same time. This feature
effectively doubles Fibre Channel's band width to 2 Gbps. SCSI
functions in one direction, either read or write. Fibre Channel
overcomes many of the limitations of SCSI.
Does this mean that SCSI is dead? No. In our experience technological
shifts of this magnitude occur over long periods of time and, in many
cases, both technologies co-exist for prolonged periods. We would refer
to this migration as evolutionary, not revolutionary. We predict that
both connectivity solutions will co-exist for another five to ten years,
albeit at a diminishing rate.
Fibre Channel Traverses Greater Distances
When storage was directly connected to servers, a short SCSI cable did
the job. With the expansion of data and the desire to centrally locate
and manage storage, SCSI's short distance limitations have lent Fibre
Channel another leg-up. While SCSI reaches distances of 12 meters, Fibre
Channel can span up to 10 kilometers.
Fibre Channel vs. Ethernet
Backing up in time for a moment, Fibre Channel actually came to the
market in the late eighties to be a data communications networking
technology; in other words, instead of using Ethernet one would use Fibre
Channel. In fact, Ancor Communications, one of the current leaders in
Fibre Channel networking, was founded in the late eighties as a LAN
company.
The benefit of Fibre Channel was that it could transmit larger packets of
data effectively (referred to as "block level" data transfers), while
Ethernet was more focussed on small packets. In the end, Ethernet won
because of its backing by the government and its broad-based support from
multiple organizations. Note, there was no real need at the time to send
block level data over the LAN, that was being handled behind the server
by SCSI which at the time did not have a demand to be networked.
In the mid 1990's, when SCSI began to look like it was running out of
gas, companies such as EMC and Brocade began to realized the benefits
that Fibre Channel could bring by networking storage.
Fibre Channel Components
Disk drive suppliers and component manufacturers also realized the
benefits that Fibre Channel components could offer. Today, Fibre Channel
technology is not only used for connectivity between servers and storage,
it is also becoming a preferred component technology. The benefit of
Fibre Channel components are 1) their ability to provide thinner internal
connectivity within systems, thereby enabling smaller systems, 2) that
they produce less heat, and 3) that they enable faster transmissions.
For example, Network Appliance was able to triple its Filers' capacities
to 1.4 terabytes, simply by using Fibre Channel drives instead of SCSI
drives.
Ethernet's TCP/IP Started Out Servicing Government
TCP/IP was originally design by the US Department of Defense and largely
used in governmental agencies and universities. However, it was the use
of TCP/IP to develop the Internet that gave it the ultimate upper hand
over competitors such as Novell's SPX/IPX and IBM's SNA protocols.
Ethernet Is Cumbersome
Ethernet uses a TCP/IP stack (Transmission Control Protocol/Internet
Protocol). The TCP part is for data transmission (what is being sent)
and the IP part is for communication (where to go and how to get there).
Ethernet works well for small bits of information, but generates too much
overhead and is too unreliable to effectively transmit larger blocks of
data.
The overhead in TCP/IP is partly a result in its smaller framing size (1k
frames), relative to Fibre Channel (2k frames which can be grouped
without interrupting the host). Further, TCP/IP often routes each frame,
or packet, differently; whereas Fibre Channel logically groups packets.
The result is that TCP/IP often drops and/or loses packets of data when
the network becomes congested. Lost data must then be retransmitted.
TCP/IP also has a more cumbersome instruction set (over 5000 instructions
per stack versus a few hundred in Fibre Channel), which requires the
utilization of more CPU cycles than Fibre Channel. While TCP/IP does the
job for file level data on the LAN, it does not currently meet the
performance requirements of block level storage transmissions.
Okay... let's look at this in a way that is easier to understand. Think
of a wooden log that you need to transport between point A and point B.
The log represents the data. Ethernet takes the log at point A, puts it
through a wood chipper, sends the various pieces to point B through
multiple paths, loses pieces along the way and reassembles the log at
point B. On the other hand, Fibre Channel takes the log at point A,
breaks it into a couple of pieces, establishes a dedicated connection to
point B, links the pieces together end-to-end, transfers the pieces to
point B over the dedicated connection and reassembles the log at point B.
There is not any debate that Fibre Channel is a more robust block level
data transfer technology! Also note that Gigabit Ethernet, although it
raised its data transfer rate 10x by moving to 1 Gbps, only increased its
throughput by approximately 3x as a result of its high overhead (one
could argue the increase is 2x or 4x, depending on the method of
measurement). Therefore, we believe the argument that Ethernet is
growing to higher capacities is largely irrelevant. In our view, in
order for Ethernet to match Fibre Channel it must reconfigure its
protocol.
We believe two solutions have been in the works to make Ethernet TCP/IP
more robust. The first is stacking encapsulated SCSI over TCP with IP.
The second approach is to beef up the current TCP/IP protocol to function
more like today's Fibre Channel. We believe either approach would take
many years to develop.
The Only Available Solution Ready For Primetime Today Is Fibre Channel
In the end, IT (Information Technology) professionals need a solution
today! The promise of Ethernet is, in our estimation, at least two or
three years out. Even then the revised protocol must gain the support of
broader industry groups to work in a unified direction to create hardware
and software support. Also, the resulting Ethernet stack will not be
compatible with today's Ethernet, so significant additional customer
investments must be made to effect the migration. We believe there are
going to be a heck of a lot of Fibre Channel networks deployed between
then and now and we have yet to met an IT professional who is in favor of
coldly abandoning a technology which they have spent years installing.
Therefore, we have to conclude that Fibre Channel will be around for some
time.
While we have heard some very good arguments that IP is a preferred
protocol as a result of its broad acceptance and use on the Internet, we
believe it is many years away from being able to service block level
storage data traffic reliably.
What Has EMC Said And Done On The Subject?
We believe EMC helped start this whole debate back in December of 1995
when it bought McDATA Corp., which was one of the first Fibre Channel
networking companies. Since then EMC has generated over $2 billion of
Fibre Channel revenues. Although these revenues are not all Fibre
Channel networking per se, we believe it is an interesting statistic in
light of today's debate.
EMC's Recent Announcement Of SRDF Over IP Is What Has Ignited Today's
Debate.
One of EMC's most recognized developments has been its ability to
remotely mirror multiple Symmetrix storage subsystems in multiple
locations real-time. The benefit of this is the ability to recover from
a Disaster in which all systems in one location fail; this is why its
referred to as Disaster Recovery (DR). The lack of being able to recover
data can cost companies millions of dollars in past, current and future
business.
Historically, remote mirroring has gone over leased T1 lines in order to
interconnect multiple sites; remember, IP is not robust enough to handle
block level storage traffic effectively. Recently, EMC announced that
its Symmetrix Remote Data Facility (SRDF) is available over IP. So now
IT managers can take advantage of the Internet and cut costs be using
SRDF over less expensive IP instead of having to lease expensive T1
lines? No!
Yes SRDF can go over IP, but not for Disaster Recovery as a result of the
high latencies associated with IP. EMC's SRDF over IP only supports
asynchronous applications. In other words, you can only use SRDF over IP
for static applications such as Internet content. We believe this
actually opens up new opportunities for EMC which complement SRDF's DR
functions.
EMC Has Entered The NAS Market To Offer Direct File Access Over IP.
A second application EMC is using IP for is to attach storage directly
onto Ethernet LANs in order to serve up file data directly to clients
(note: file data, not block level data), this is usually referred to as
Network Attached Storage or NAS. EMC's NAS solution connects a
Symmetrix directly to the LAN through its Celerra File Server. EMC can
also connect that same Symmetrix to a Fibre Channel based storage network
behind the server to keep block level data transfers separate. Notice
the convergence of storage networking behind the server (SANs) and
storage access directly on the LAN (NAS).
EMC Is Agnostic To The Debate Between Ethernet And Fibre Channel.
We believe a third application EMC is anticipating is Ethernet
connectivity between servers and storage. At the same time, it is our
understanding that EMC sees storage networking traffic remaining separate
from file data traffic. In other words, even if Ethernet TCP/IP were
just as robust as Fibre Channel, storage and datacom networks would
continue to be separate.
If the networks do, in fact, remain separate, we believe this will
benefit Fibre Channel storage networking which is continually gaining
momentum. We believe Fibre Channel and Ethernet networking technologies
will begin to overlap in the three to five year time frame.
EMC has told us that they do not foresee any precipitous change in the
storage networking landscape in the next two years. In other words,
Fibre Channel will continue to be the most robust block level data
storage networking technology for the next two years. Furthermore, they
do not have any preference as to which technology customers ultimately
favor.
Brocade's Move To Partner Up With ONI
We believe Brocade's recent ONI (Optical Networks) partnership
represents a significant shift in the dynamics of networking. The
agreement promotes Fibre Channel to fiber-optic connectivity across
Metropolitan Area Networks (MANs). We believe partnerships between voice
networking, datacom networking and storage networking companies has been
imminent. We believe Brocade has been strategizing with most major
networking companies in an effort to create synergies between various
networking platforms. We believe Brocade will continue its efforts to
leverage its core competencies across other networking platforms,
including Ethernet and ATM. In the end, we believe Brocade is a storage
networking company, not a Fibre Channel networking company.
It is important to note, the most robust storage networking platform
available today is Fibre Channel. Therefore, companies such as Brocade
use Fibre Channel. Many Fibre Channel networking companies are working
to develop networking capabilities across a wide variety of networking
platforms. Evidence of this can be seen in Gadzoox (ZOOX, $57.75, 3H)
recent acquisition of SmartSAN. SmartSAN has been developing Fibre
Channel to ATM and Ethernet connectivity. Note: we believe any competing
storage networking platform is at least two or three your away and will
take much longer to gain broad based adoption.
We expect many announcements similar to Brocade's ONI partnership
throughout this year and well into the future. |
