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Adventures with a Lego-cased A7K web server

By Peter Howkins. Published: 21st Nov 2008, 19:49:07 | Permalink | Printable

Having previously built desktop and laptop cases of out Lego bricks, model building Peter Howkins has turned his attentions towards crafting a slim box to slid his A7000 into a rack, alongside other rackmount servers. Having pieced together the housing, Peter puts a legacy RISC OS machine through its paces as an internet-facing server.

As an offshoot of my cunning project to create a 1U size case for my A7000 out of plastic Lego bricks, I pondered the suitability of actually running the ARM7500-powered computer as a server. This is 13-year-old hardware so I rightly can't expect modern performance, but can the A7000 fill some sort of low-power, power-efficient server role? I decided to investigate this by testing various bits of server-related software available for RISC OS, having assumed the computer will be used as an unattended machine in a rack hooked up to a network. As it will not have a monitor or keyboard attached to it, I also decided to attempt to address the need to monitor and control it remotely over said network.

The contenders
To start, my Acorn A7000, manufactured in 1995. Its vital statistics are:
  • 32MHz VLSI ARM7500 processor
  • 68MB RAM, 4MB onboard, 64MB SIMM
  • RISC OS 3.60
  • EtherH network card
  • IDE-to-Compact flash card adapter
  • 2GB Compact Flash 'hard disc' with a RISC OS 4.00 softload from Pace
  • Custom 1U rackmount case, made from Lego, with internal fluorescent tube light and no fans.

Pictured is the A7000 server in the Lego rackmount case, sitting in a rack, and, right, dismantled. Click on a thumbnail for a full image.

I intended to compare the A7K with a PC, namely this HP dx2000, manufactured in 2004:
  • 2.8GHz Intel Pentium 4 (Prescott A)
  • 1GB RAM
  • 40GB IDE hard disc
  • Solaris 10 operating system
  • Standard desktop ATX mini-tower case

Services provided
Compared to other server platforms, RISC OS (as a primarily desktop OS) offers fewer services. However several internet and file/print sharing services are available, such as HTTP, FTP, SMB, NFS and Access(+). For the sake of this article, I'll only be comparing HTTP servers, of which RISC OS has several. A HTTP server works by setting itself up and then waiting for web browsers to send it requests for pages, images and other documents. The web server locates and serves the documents, which could be stored on a hard disc or generated on-the-fly or a mixture of both, by sending them back to the clients, which then display or do some other work on them.

Here are the HTTP servers available:

  • Webjames - 0.48 - 05/05/2007 - A largely capable web server with support for CGI, SSI and PHP (available as a separate or combined download). Freeware.
  • Serviette - A recent web server, supporting Python scripting. Commercial.
  • NetPlex - 2.01 - Supports CGI scripting in Perl, PHP and SHTML. Commercial.
  • h11p - 1.31 - 11/06/2006 - Included only for my own amusement. It's a web server that measures just 1KB in size and is not even HTTP/0.9 compliant. Freeware.
  • InetD/micro_httpd - Included only for my own amusement as it's my unfinished InetD with a port of Acme's micro_httpd. Unavailable.

The following servers have been available in the past but have proved difficult to find for testing purposes:
  • HttpServer - A simple server, written in BBC Basic, by Stuart Brodie. Freeware.
  • DeltaNet - A large package of servers including HTTP. Shareware.
  • AlphaNet - A commercial development of DeltaNet. Commercial.

A primary concern of a remote server is the stability of the software and hardware. Having to reboot a server in normal operation should not be expected because, among other reasons, services are unavailable during this process. After some initial concerns, RISC OS proved stable enough to provide five days of up time without issues and may provide more if I were to test it more thoroughly.

Environmental factors
Adequate cooling needs to be provided to any server with heat sensitive components. For the A7000 in this project, I replaced the standard issue hard disc with an IDE-to-Compact Flash adapter and a Compact Flash card. Cooling requirements for the server are not on the radar as all the components run at room temperature even under load; there's simply no need for a fan or such device. Power usage of the A7K, being a modest ARM-driven machine, should ideally be low, or at least offer a good power/performance trade off. The power draw measured on the A7000 was 11W while under web serving load and 10W idle. My comparison desktop PC pulled 99W under similar load and 75W idle.

Remote management
Being able to control a machine remotely is important in a server product so that changes can be made and fixes installed without having to be on-site. Racks of servers are predominantly locked away in large warehouses, where they can be closely coupled to internet backbones, kept in cool and machine-friendly conditions and watched over by security guards. The downside to housing machines in data centres is that it's a chore to go on-site to fix them, hence the requirement of stability and remote management.

Here's what I uncovered:

  • SSH - This provides a secure and encrypted method for connecting to a remote host, but such a service is not available for RISC OS, and also generally unsuitable due to the graphical nature of RISC OS applications. This is the de facto standard for remote access on UNIX and UNIX-like OSes.
  • Telnet - A telnet server exists for RISC OS. One again due to the graphical nature of most RISC OS programs (and their configuration) coupled with telnet's extremely poor password security I would not recommend it.
  • VNCServer - A VNC server, for 26bit and 32bit RISC OS machines, provides 'slow' access to the RISC OS desktop from pretty much any client OS available. Due to its graphical nature, it's easy to configure and control all programs. VNC works like Windows Remote Desktop, in that you can remotely view the server's desktop and interact with it using the mouse and keyboard connected to the computer running the VNC client. However by default VNC security, whilst considerably better than telnet, is poor and susceptible to determined malicious folk. Appropriate firewall rules to prevent access from most IP addresses would be advised.

Perhaps as a last resort this project would benefit from the server being attached to a network-accessible power rail, with the ability to remotely power cycle it - effectively switching it off and switching it back on again when a problem occurs using a power supply that's connected to the network.

Remote monitoring
Being able to see the state of the server, or even if it's running at all is useful. The normal protocol used for this purpose is SNMP, of which no RISC OS server is currently available. Ideally the solution would need to provide the following information live:
  • CPU usage
  • Memory usage
  • Disc space usage
  • Network bandwidth usage

The closest RISC OS software I can find to providing this is Chris Williams' Status Daemon* which may provide enough information.

Benchmarking of HTTP servers
Each of the server software packages were benchmarked one by one on a local area network with one ethernet switch between the test host (a PC running Linux Ubuntu 7.10) and the target machine. All tests were run using 'ab' (Apache benchmark), which measures how many requests for web pages the server can handle per second. The Linux PC was therefore told to fire requests for 1,000 1KB and 100 25KB pages at each of the HTTP servers. Two levels of concurrency were also used, one being one request sent at a time and five being that many requests sent simultaneously. In the real world, web servers are constantly bombarded with multiple requests at the same time and this tests the software's ability to handle multiple clients.

The RISC OS servers were also allowed to run and serve pages stored on the RAM disc. On RISC OS servers, logging of requests was disabled. The comparison PC was running the Apache 2.2.6 web server.

Example 'ab' usage:
ab -n 1000 -c 5

ServerPage SizeStorageConcurrencyReq/sTransfer Rate (KB/s)
RISC OS - A7000
h11p1 KBDisc116.7318.07
h11p1 KBDisc516.7218.06
h11p25 KBDisc17.78194.99
h11p25 KBDisc57.79195.03
h11p1 KBRAM116.6517.98
h11p1 KBRAM516.6517.98
h11p25 KBRAM18.45211.69
h11p25 KBRAM58.49212.67
InetD/micro_httpd1 KBDisc14.615.53
InetD/micro_httpd1 KBDisc54.585.50
InetD/micro_httpd25 KBDisc12.8371.43
InetD/micro_httpd25 KBDisc52.8471.66
InetD/micro_httpd1 KBRAM15.136.16
InetD/micro_httpd1 KBRAM55.116.13
InetD/micro_httpd25 KBRAM13.3584.55
InetD/micro_httpd25 KBRAM53.3484.10
WebJames1 KBDisc115.8817.47
WebJames1 KBDisc514.9716.47
WebJames25 KBDisc17.85196.26
WebJames25 KBDisc58.52213.04
WebJames1 KBRAM116.7518.42
WebJames1 KBRAM517.8619.64Fastest RO Req/s
WebJames25 KBRAM18.27206.67
WebJames25 KBRAM59.08226.97Fastest RO KB/s
Solaris - PC
Apache 2.2.61 KBDisc11587.251949.14
Apache 2.2.61 KBDisc52353.662890.30
Apache 2.2.625 KBDisc1340.578592.56
Apache 2.2.625 KBDisc5445.8211248.13

It seems that running and serving from RAM disc provides a 5 to 10 percent performance boost for all the RISC OS servers, except for some cases of h11p. WebJames comes out as the fastest RISC OS server, managing up to 17 requests a second or 226KB a second, depending on the size of the page. Unsurprising, the 2.8GHz Intel-powered machine blew the A7K out of the water with 2,353 requests a second or 10MB per second. Given the low-power consumption of the RISC OS platform, and the particulaly high consumption of the P4 in the comparison machine, I calculated the following metrics to see if the little A7000 fared better:

Requests per Second per Watt
ServerPower (Watts)Req/sReq/s/Watt
RISC OS (Web James)11W17.861.62
Solaris (Apache 2.2.6)99W2353.6623.77
KiloBytes per Second per Watt
ServerPower (Watts)KB/sKB/s/Watt
RISC OS (Web James)11W226.9720.63
Solaris (Apache 2.2.6)99W11248.13113.61

And here's the utilisation of underlying network transport, maximum theoretical throughput, excluding ethernet, IP, TCP and HTTP protocol overheads:

ServerNIC Type and Max throughputKB/s% of Max
RISC OS (Web James)10 Base T (10 Mbit/s 1280 KB/s)226.9717.73%
Solaris (Apache)100 Base T (100 Mbit/s 12800 KB/s)11248.1387.87%

It appears possible that the comparison PC is being limited by availabilty of network bandwidth. An upgrade to 1GBit/s networking might prove useful.

I'll be blunt. Using 13-year-old hardware for sensible things is a bad idea. My A7000 offers slow performance for low absolute power requirements. However it appears that even the famously power inefficient Pentium 4 architecure in a 4-year-old PC out-performs it significantly in power-based metrics. Looking beyond the fact that the meaty P4 can happily cope with over 130 times the number of requests for pages than the A7K, it still delivers more performance per Watt.

A case could be made that an A7000 could be suited to a low-traffic website when the server would spend most of its time idle. However an even more efficient solution would be to virtually host such a website on a server with other sites hosted on as the small site would barely take up any additional power at all when hosted alongside other sites on a PC solution.

The increase in performance when using RAM disc to serve files suggests that RISC OS may benefit from a cache of recently-accessed files, which would be held in RAM. It is faster to fetch a file from memory than from a hard disc or even Compact Flash and most modern operating systems employ this technique of disc caching.

However I'm not entirely dismissive of the use of RISC OS hardware as a server, and am interested in running future benchmarks on a StrongARM RiscPC and an A9home. As I expect the increase in performance (without
the corresponding increase in power requirements) may prove more competetive. But in fairness more power efficient PC architetures such as Intel Core2 and Intel Atom should also be investigated.


A7000 in a Lego rackmount case * As a declaration of interest, StatusDaemon was written by Drobe editor Chris Williams.

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But, but, but! RISC OS kit uses less power!

 is a RISC OS Userrjek on 21/11/08 11:54PM
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Great article and really interesting little project. I am very interested in knowing how newer RISC OS machines perform and just for fun , throw in stats from a HP DL360 G5 :-)

 is a RISC OS Userstevek on 22/11/08 5:59AM
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What screen mode was used?

I found with a microdigital mico using high screen modes really hammered the performance. (And the mico has significantly faster hardware than the A7000).

 is a RISC OS Userjess on 22/11/08 10:26AM
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The mode was 640x480 in 8bpp colours. In theory a drop to 16 colours would halve the video bandwidth used. However if I remember correctly the VNC server recommended 8bpp.

The Mico should have had more performance that an A7000, the Mico being closer in design to an A7000+

 is a RISC OS Userflibble on 22/11/08 1:08PM
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I remember old machines blanking the screen to get more processing power (I know the ZX81 did it, but seem to remember it being an option on old 3.1 machines.) I wonder if this would be a possible upgrade? (even if it were a DPMS style screensaver.)

 is a RISC OS Userjess on 3/12/08 2:07PM
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Fascinating project and a great write up. In all fairness to the A7000, it wasn't designed to be especially low powered as it's a desktop workstation. That said, I suppose an old PC laptop would be even more power efficient.

I too would be interested to see how a SA would fare. I wonder how much of the inefficiently is caused by RO itself? Another interesting comparison would be between ARM Linux and RO on the same hardware.

 is a RISC OS Userkillermike on 23/11/08 10:03AM
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I'd expect ARM Linux to comprehensively demonstrate the folly of using RISC OS as a server, even on exactly the same hardware. :(

 is a RISC OS Userdruck on 24/11/08 9:10AM
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I had initially planned on benchmarking NetBSD alongside RISC OS on the A7000. However <a href="[link]">my adventures</a> with NetBSD suggest that the A7000 and Risc PC are no longer supported platforms (in reality as opposed to what the web pages say).

I did for a short time manage to get NetBSD 3.1 working on it long enough to benchmark one server. It got a peak transfer of about 210KB/s, which is almost identical to RISC OS.

This surprised me rather a lot and left me wondering if there was a hardware limit I'd run into.

 is a RISC OS Userflibble on 24/11/08 10:08AM
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I think the A7000 hardware is indeed too puny for you to get meaningful results, here. I suspect the performance difference between RISC OS and Linux on, say, a StrongARM RiscPC, would be somewhat larger.

 is a RISC OS Userrjek on 24/11/08 10:12AM
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Well, when you benchmark them you'll be able to say for sure, until then it's just hot air.

 is a RISC OS Userflibble on 24/11/08 10:19AM
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Neat article. A mad project but wonderfully technical. And what a fun thing to do with old kit. I like it !

 is a RISC OS Usermartin on 29/11/08 4:44PM
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