Timothy
Parker Consulting Incorporated
|
|
|
|
Tarantella and Metaframe Application servers like SCO Tarantella Citrix MetaFrame
for UNIX and designed to allow a server to provide UNIX and Java applications to
almost any type of client machine, usually UNIX and Windows machines attached to
the network. Most application
servers work in the old mainframe or minicomputer model whereby clients are
relatively unintelligent terminals and all the application execution gets
performed on the server. While a
server-centric design by its nature imposes a heavy load on the server (which
has to handle not only all the applications being run but also the task of
handling the client interface communications), the design does allow virtually
any type of client to connect over any type of connection and achieve reasonable
execution rates. There are a lot of trade-offs when considering an
application server model for your business.
First, the advantages are relatively straight-forward: access to any
application on the server from any type of client and over any type of
connection, lower-cost client machines can be used, common application data
access is available for all clients, and applications need licensing for only a
single server installation instead of a bunch of clients.
The obvious disadvantages are also straight-forward: a powerful (and
usually expensive) server is needed to keep up with the application demands,
application server software must be bought and configured, and clients may not
experience the performance they would with local applications. Whether the advantages outweigh the disadvantages is a
matter for each installation to decide. In
general, application servers work extremely well under specific circumstances.
If you have a bunch of legacy equipment being used as clients, or there
is the need to connect over a variety of different (and sometimes slow)
connection methods, application servers can be an inexpensive means of providing
faster execution. If your
applications are server-centric anyway, such as databases that must reside on a
single host, then application servers can be more efficient and cost effective
than traditional distributed computing methods.
If licensing of applications is an issue, where you need to provide only
a fixed number of floating licenses to a larger user base, application servers
can also be cost effective. And if
you need better control of your network applications, then application servers
provide centralized management, administration, and security. Traditionally, UNIX systems were application servers.
When SCO servers were first set up, dumb terminals accessed the
applications on the server over standard serial lines or modems.
The server hosted the client sessions, as well as the applications.
As client machines became more intelligent and powerful (especially with
the development of personal computers and Windows), the urge to move processing
off the UNIX server into the clients provided better performance for users and
off-loaded the servers. Windows NT
provided a familiar environment for many administrators to resort back to
application servers for traditional server-centric applications like databases
and order-entry systems. And still
the tide swings back to application servers for many more applications,
especially since the mobile workforce has expanded.
Being able to connect to a central server from a laptop or smaller device
like a PDA still gives access to the applications used in the main office
through an application server. That’s
a market that was addressed by Citrix with their WinFrame product several years
ago. SCO tackled the same market
with Tarantella a couple of years ago. Now,
Tarantella has evolved into a new version, and Citrix has introduced MetaFrame
for Windows and MetaFrame for UNIX, both evolutions of the WinFrame product. This review takes on both SCO Tarantella and Citrix
MetaFrame as application servers. We assembled a test network based on a 100Mbps
Ethernet network, and configured three servers: one with SCO Tarantella, one
with Citrix MetaFrame for Windows NT, and one with Citrix MetaFrame for UNIX (MetaFrame
for UNIX runs under Solaris). We
loaded the servers with a variety of applications including traditional office
suites (word processors, spreadsheets and presentation graphics), as well as
more traditional server-centric applications (two databases, an accounting
package, an inventory and order entry package, and a set of Java clients that
access data files). We accessed all three application servers from the clients
ranging from older PCs (80386s through 80486s), a set of current Pentium-class
PCs (running mixes of Windows 98, Windows 2000, Windows NT, Linux, SCO UnixWare
7.1 and SCO OpenServer 5), through modems to a set of laptops running Windows 98
and SCO OpenServer connecting at speeds from 28.8kbps up to dual ISDN (128kbps),
and from a remote network attached through dual ISDN 9128kbps) and a T1
(1.544Mbps) lines. We also used a
variety of PDAs and subnotebooks to test the access to Java clients. Two application servers (SCO Tarantella and Citrix
MetaFrame for Windows NT) were identical machines featuring dual Pentium-III
600MHz CPUs, 512MB RAM, and triple 9.1 UltraSCSI drives.
MetaFrame for UNIX runs under Solaris 2.6 and 2.7, so we configured a Sun
SPARCUltra with 512MB RAM and triple 9.1GB SCSI drives. We installed the base
operating systems out-of-the-box and did no real tuning other than setting up
network services and Web servers. All
three servers had similar applications and database contents. Accurately
comparing Pentium-class machines to a SPARCUltra machine is difficult as the two
hardware designs are not equivalent: all else being equal the SPARCUltra will
outperform the Pentium III CPU. While this apples-to-oranges comparison is not
really fair, MetaFrame for UNIX is not available for Pentium-class CPUs, so we
continued with the testing fully cognizant of the difference in servers. To arrive at performance measurements we used WinRunner and
XRunner to run scripts accessing the application servers in turn.
We set three load levels with light, medium and heavy application demands
on the servers. We timed response
times for ten different scripted tasks, as well as monitoring the server CPU
loads. We also assessed the
ease of installation, configuration, and management of the three application
server packages. Citrix MetaFrame for UNIX MetaFrame for UNIX is an extension of the popular Citrix
MetaFrame for Windows. The key to
MetaFrame for UNIX’s functionality is Citrix’ Independent Computing
Architecture (ICA). While the UNIX and Java applications all execute completely
on the server, ICA allows the presentation layer of the application to be seen
by the clients. ICA uses a
compression method to send the interface layer to the client, and returns any of
the user’s inputs to the server. MetaFrame for UNIX is installed on Solaris 2.6 and Solaris
2.7 only. Support for other UNIX variants may appear, but Solaris is the primary
UNIX vehicle for Citrix at the moment. We used Solaris 2.6 for our tests,
including the X Windows System and Iconv modules, both of which are necessary
for MetaFrame for UNIX. To install
MetaFrame for UNIX, a new administration login is created and used to handle the
install and configuration. From the
mounted CD-ROM, installation proceeds smoothly using pkgadd.
A reboot makes MetaFrame for UNIX available to clients. Administration
tasks to set up MetaFrame for UNIX for clients takes a little while, providing a
total application load time of three hours. To use MetaFrame for UNIX, all Windows clients need to run
an ICA client package. A 32-bit DLL
for Windows is provided with the system and needs to be installed on all
clients. Configuring the client requires a bit of time and is not for
non-technical people. Installing
the client on our Windows clients took another three hours, and in larger
corporate environments this step could be a considerable time investment by the
IT groups. Access to MetaFrame for UNIX is not limited to Windows machines running ICA clients. There are client drivers for some devices embedded in the MetaFrame for UNIX server, and there are stand-alone clients for other clients available. A common method of accessing the application server instead of loading clients is to use the HTML interface. Any Web-capable device could access MetaFrame for UNIX through a Web browser. Although there are limitations to the application support under HTML (not a limitation of MetaFrame for UNIX but of the HTML language itself) this does provide very broad client support. Setting up UNIX applications for access through the HTML interface takes a while, and requires a fair amount of trial-and-error on more complex interfaces for applications. In testing the Solaris platform running MetaFrame for UNIX proved stable, with no application problems at all. The system didn’t have a core dump or any other anomaly during the testing period of two weeks. Citrix MetaFrame for Windows MetaFrame for Windows is similar to MetaFrame for UNIX
except designed, as the name suggests, to run on a Windows NT server and provide
access to Windows applications. Installation
and configuration of MetaFrame for Windows is straight-forward, mirroring many
of the steps of the UNIX variant. Configuring
Windows applications for use by MetaFrame for Windows takes as much time as
configuring UNIX applications under Solaris, so there is not much time
difference in the installation and configuration procedures.
Where some time may be saved is in the HTML interface, as many Windows
applications are easily made Web-aware. Our MetaFrame for Windows installation started on a Windows
NT 4.0 machine running Service Pack 6, and ended with a fresh install on Windows
2000 Professional. Under both
platforms we did experience some application problems, both with the
applications being accessed by MetaFrame for Windows and in MetaFrame for
Windows itself. In a two week
testing cycle we recorded three MetaFrame for Windows crashes, usually under
heavy client testing conditions, and most likely caused by the applications
themselves. We had one total
machine crash under Windows NT 4.0 and two under Windows 2000 Professional.
However, in normal load usage (light and medium load conditions)
MetaFrame for Windows behaved fine under both operating systems.
Whether the problem lay with applications, Windows itself, or MetaFrame
for Windows we didn’t investigate. SCO Tarantella Tarantella Enterprise II is the latest version of
Tarantella (we looked at Tarantella in some detail in earlier issues of SCO
World). Tarantella is designed as
an application server which resides on several platforms including SCO
OpenServer, SCO UnixWare, HP-UX, Solaris, and AIX. Access to a Tarantella server
is mostly through Web browsers. Tarantella
uses Adaptive Internet Protocol (AIP) for communications between the application
server and clients. AIP employs a
compression algorithm and allows access to the server over slow
telecommunication links, as well as through networks. Is this an important issue? Can integrate and handle windows applications by
connecting to a Windows NT Server using Microsoft’s Remote Desktop Protocol (RDP).
Alternatively, Windows application can be handled on the UNIX server using SCO
Merge. The former is the more
efficient solution in most cases unless there are few Windows applications that
need handling. Tarantella is
designed more specifically for Windows clients than a wide variety of other
devices. A minimum recommended
client has an 80486 processor and a Web browser.
While not onerous requirements by any means, Tarantella does prevent
access through some of our test devices like PDAs and subnotebooks. Installation of Tarantella is quick: mount the CD-ROM, run
an installation script, add a couple of directories, and configure the software
through an HTML interface. The process took us just over an hour.
There is no software required on the clients as all access is through a
Web browser. Administering
Tarantella takes a bit of time, but nothing too time consuming.
Ongoing maintenance is about the same as MetaFrame. During the testing
period of two weeks the Tarantella server on UnixWare behaved perfectly, with
nary a hiccup. Summary Before discussing the performance results, it is
interesting to note that with both UNIX and Windows application servers on the
same network, each one of our clients had access to the best applications from
both operating systems. We could
very easily switch from a UNIX-based database to a Microsoft Office tool, and
cut-and-paste data between the two on most clients.
With many legacy UNIX applications still in use in many businesses, the
combination of the two environments as application servers seemed to provide us
with the best of both worlds. Both products (SCO and Citrix) allow load balancing and
arrays of servers, balancing application demands across primary and secondary
servers. This can be important as
companies expand and the servers are placed under more load, or simply to handle
short-term demands on a secondary server. Both products distribute users
according to load balancing algorithms that worked well, resulting in no notable
performance difference between the two. One difference we noted between SCO Tarantella and Citrix
MetaFrame is the two protocols used to communicate between the application
server and clients. Citrix uses ICA
while Tarantella uses AIP. While
both protocols work just fine and we couldn’t see any real performance
difference between the two, a close look at the packets of the protocols shows
one possible weakness. Both
protocols compress and encrypt data to some extent, but the Citrix ICA seems
weaker than AIP. Indeed, it appears
that the ICA protocol could be hacked with less effort than AIP, making
communications a bit more susceptible to interception and decoding.
To beef up ICA third-party encryption software can be used, but this adds
more cost and processing to the process. Tarantella
does provide an add-on Security Pack which uses RSA encryption, but again this
is an extra layer of software that must be processed. Is this an important
issue? Probably not, but under some
corporate conditions it may be necessary to evaluate these protocols for
security. Performance measurements were interesting but in the end,
mostly useless. When the numbers
are analyzed, both Tarantella and MetaFrame provide roughly equivalent
performance to the end clients, behaving within a few bytes of each other over
modems from 28.8 to 128kbps. On a
network, the MetaFrame product served up applications a touch faster than
Tarantella, but the administration overhead for MetaFrame is higher than
Tarantella’s. MetaFrame for UNIX
performed better than MetaFrame for Windows but that’s a direct effect of the
processors in the UltraSPARC, which are faster than Pentiums.
Also, UNIX (both SCO and Solaris) tends to outperform Windows NT in heavy
loading situations. As noted earlier, the Windows platform was the only one to
crash on us, and we suspect that’s a function of the operating system and not
MetaFrame. Both MetaFrame and Tarantella use proprietary protocols for
their application servers, although AIP is more open than ICA.
Both products perform approximately the same in the end, with neither
having an edge over the other. There’s
an interesting spin to the MetaFrame vs. Tarantella debate when it comes to ASP.
Although ASP is still young, the use of a proprietary protocol by Citrix
(ICA) may lead to incompatibilities later. Choosing between MetaFrame and Tarantella is going to be a
choice between two approaches for handling clients and Web interfaces.
Tarantella uses the Web for most tasks, while MetaFrame uses the Web as
an option. On the other hand,
MetaFrame requires a client package on the client or server (as an embedded
driver) while Tarantella doesn’t require special client software at all.
Tarantella uses the Web for everything, MetaFrame allows a choice between
the Web and native interfaces. The
latter will be a more user-friendly approach for Windows-centric networks. If you are choosing an application server then Tarantella is really the only choice, at least until Citrix releases a version of MetaFrame for SCO. If you have a choice between Windows NT and SCO, then the choice would most likely be SCO Tarantella unless you have to serve up primarily Windows applications. Finally, the choice between Solaris-based MetaFrame for UNIX or SCO Tarantella for SCO UnixWare or OpenServer is more difficult; the latter is a lot less expensive a platform than Sun’s UnltraSPARC, but the UltraSPARC is faster. That’s a debate bordering on apples to oranges, so we’ll leave it to you to decide. MetaFrame for UNIX Summary: Provides both HTML and specific interface
application servers. Requires
client software. UNIX version robust and talented. Tarantella Summary: HTML-specific application server with better security and more open protocol than MetaFrame. Under UnixWare is very robust. |
|
Send mail to
tparker@tpci.com with
questions or comments about this web site.
|