Summary:

Our experience at Brandon running K12LTSP has found the following hardware configurations to be suitable:

• CPU: PII 300 or faster. CPUs in excess of 1 ghz may run applications locally.
• RAM: 32mb (up to 256)
• NIC: Motherboard or PCI slot. Netbootable preferred: PXE or Etherboot ROM (requires floppy if not).
• Video: 4mb RAM
• Storage/drives: None (except for floppy drive in case of floppy etherboot but this is to be avoided if possible).
• Other requirements: Small form factors eg. Mini-itx, Flex-atx, slim desktops preferable.
• Monitors: Restricted by video RAM available but typical supported resolutions are 800 x 600 and 1064 x 768.

• Classroom 2-4 stations: PIII 1 ghz or AMD equivalent or faster, 512mb RAM, 7200 rpm 20GB IDE hard drive, CD-ROM, 2 NICs.
• Classroom 3-6 stations: P4 or AMD equivalent (Celerons and Durons not optimal but useable) 1.5 ghz, 768mb - 1 gb RAM, 7200 rpm 40gb IDE/SATA hard drive, CD-ROM, 2 NICs.
• Computer Lab 10 users: P4 or AMD equivalent dual-core 2.8 ghz, 2 gb RAM, 10k SATA drive, 2 NICs (one gigabit), DVD/CDR burner.
• Grade Level 30-40 non-concurrent users: P4 or AMD equivalent dual-core 3.2 ghz, 4 gb RAM, 2 x 10k SATA drive RAID 1 array, 2 NICs (one gigabit), DVD/CDR burner.

Discussion

Morris Brandon is implementing the K12LTSP package as a "proof-of-concept". K12LTSP is a Linux Terminal Server Project focused on the K-12 educational environment. It uses a server, running Fedora Core Linux, powering "thin clients", which can be new, small footprint appliances or older legacy PCs. All applications run on the server - the clients merely display the video stream. More importantly, the K12LTSP package delivers a wide variety of educational applications ranging from language to chemistry, math, astronomy, computing and more. Below is a more in-depth description of what we are using and our experiences.

Clients: We use a mix of donated and system-provided clients ranging from PII 350 mhz to P4 1.4 ghz and AMD equivalents. We also use purpose built clients in the computer lab using Via Mini-ITX EPIA M Eden motherboards witih 600mhz Cyrix CPUs. These clients, being fanless, have no moving parts. In theory, clients with CPU speeds in excess of 1 ghz can run many or all applications locally (not off the server) although in practice, we haven't done this because of the small number of such powerful clients. The other requirement is that the video card have at least 4mb of memory.

Other LTSP (and K12LTSP) installations reportedly can and do use even weaker clients, down to PI 150 but we've done little in the way of experimenting with these given the plethora of more powerful clients available.

Almost all clients are netbootable either via a motherboard network connection using the PXE protocol or a bootable ROM on a network PCI card (Etherboot). In rare cases, we've used an Etherboot floppy which allows a network card without a bootable ROM to network boot. The advantage of this is that it saves the $20-30 cost of a bootable NIC. The disadvantage is that it relies on the floppy drive. The Etherboot floppy image and instructions are included as part of the K12LTSP installation in /tftpboot/lts/boot/bootroms .

We remove hard drives from donated computers as they are superfluous, might have software with restrictive licensing (read: Windows) or contain personal data of the donee. We also disconnect any other drives as, again, they are not needed and only create noise and heat. Lastly, we enter the bios, and if net or net/floppy booting, set the bios appropriately.

Servers: We use a range of servers in the classroom. Linux is much more CPU friendly than other operating systems and we've found that PCs that struggled under other OSes, thrive. Even something as modest as a PIII 1 ghz (or AMD equivalent) functions fine as a desktop and serving 2 or even 3 other clients. Processors with more cache - Pentium instead of Celeron - do better, too.

We upgrade all servers to a minimum of 512 mb RAM. By using net vendors such as newegg.com or chiefvalue.com, RAM can be upgraded at a modest cost - even as low as $80-90/gb (RAM used in current desktops tends to be cheapest). More powerful servers easily use 1 GB of RAM. Servers in the computer lab have 2 GB and grade-level servers, 4 GB. Having a lot of RAM keeps the server from using swap space (hard drive as memory) and boosts performance. The server usually takes 250mb for itself and from 50-150 mb per client. We have successfully run servers with less than 512 mb of memory but it's a worthwhile investment to have 512 as a minimum.

All classroom servers are also upgraded with at least 7200 rpm drives. The most powerful servers use 10k rpm SATA drives. The K12LTSP package takes up a modest amount of disk space (6-8gb including applications) and even older 20gb drives have been used. New drives can be had for around $50 - spending more usually isn't worth it because of the small disk footprint of K12LTSP (see more below).

Any server serving six or more clients should use a gigabit ethernet connection to the clients as we've found Flash animations and other video intensive applications send 10-15 mb/sec per client on the network. More than six clients will overwhelm a 10/100 connection from the server slowing all activity to a crawl. The connection from the server to the switch only needs to be gigabit; from the switch to the client, 10/100 is totally adequate. We use off-the-shelf 24 + 2 switches, having 24 10/100 ports and 2 gigabit ports (of which, typically, only one is used).

While in the classrooms, we have a mix of servers - with a number of converted Celeron 1.8 ghz from the computer lab - all working well, we use more powerful servers in the current lab setup. The computer lab differs from the normal situation where a number of users are doing different and diverse activities, often not at the same time. In the computer lab all users could be doing exactly the same thing at the same time - e.g. a processor and network intensive Flash application such as Accelerated Reader. Thus, performance is at a premium per a given number of clients. With the advent of dual-core CPUs from both Intel and AMD, it's easy to get a lot of performance at a low cost. We built two 2.8 ghz dual core P4 servers (2 gb RAM, 10K SATA drive, gigabit NICS), each serving ten clients and a third 3.5 ghz AMD64 server (2 gb RAM 10k SATA drive, gigabit NICS) serving 5. They all easily handle their workload and we've not experienced any CPU limitation issues. These servers each cost less than a $1000 per unit.

We are also experimenting with a "grade-level" server to test the practicality of running an entire grade from a single server. Other schools have indicated that a powerful server can support several dozen clients. This server has a 3.2 ghz dual core P4 processor, 4 gb RAM, gigabit NICS and 2 10K SATA drives in a RAID 1 array. The RAID array provides not only redundancy but since most disk activity is reads, actually is faster than a single drive as the data can be read from either drive. Our objective is to serve five classrooms (around 30-40 clients) from this single server. This server was built for approximately $1400 which gives a $/client ratio of about $35-45/client.

The "grade-level" server being so powerful - and idle after 3 pm - will make an ideal testbed for using FreeNX technology. This will allow students to access school software from home using VNC-like technology over a secured connection. The compression in FreeNX means that even, possibly, students on a dialup connection will be able to access, write and edit documents from home.

The current K12LTSP package is built for 32 bit platforms which doesn't take advantage of - but is useable on - 64 bit aware processors such as the new AMD64 dual core chips (as of early 2006). A 64 bit distribution is in beta testing by the K12LTSP community and may be used at Brandon at a later date as a number of servers have 64 bit capable chips.

We are also repurposing our old Accelerated Reading server (AR is now web-based), as a file server as it has a SCSI RAID 5 array, ideal for document and file serving and storage. This will allow portability of documents around school and access from home. We'll use Fedora Directory Services as the user management protocol although SMB, NFS and others are also possible.

Summary: We've found that the K12LTSP package to make fantastic use of existing and donated resources. PCs that previously were obsolete work well as clients and those that are beginning to creak under the weight of Win XP work fine as servers. Additionally, inexpensive new servers can serve a number of clients from 10-40, depending on the likely workload pattern.