I have always felt that real hardware should be rack-mounted, and I'm thrilled to see that some manufacturers are finally getting this concept. Compaq has had very nice rack-mountable servers for years, but only recently have HP, IBM and Sun got into the high-density rack-mount server business. Some of these companies have had their larger systems available in racks, but I think the trend is towards many small, specialized servers; not monster, multi-use boxes.

If you are going to talk about racks, you need to know rack-speak.

The first term is "U", which refers to a vertical height of 1.75". The vertical dimensions of racks and rack equipment will be expressed in U's. For example, a standard 7' rack can hold 42U of equipment. The most common width of rack-mounted devices is 19", but you can also find 23" and 25".

When I think of the term rack, I think of two vertical supports. This is commonly known as a telco rack. A rack is typically used for patch panels and lightweight devices such as routers, hubs and switches. Equipment is usually mounted at its front or middle only.

When you have four vertical supports, allowing equipment to be secured both at the front and back, I would call this a "cabinet", even if it does not have side panels and doors. You need a cabinet with heavy equipment, such as servers, large UPS and devices that slide out for maintenance. Racks and cabinets are usually secured to the floor, but they are sometimes wall- mounted in smaller applications.

As for rack-mounted servers, I have been very satisfied with the 3U Compaq Proliant 1850R. This is the closest thing to a standard Web sever I have seen: It seems like every Internet company I visit has some in the computer room. They make nice Windows NT or Linux servers.

Even the high-end Compaq SCSI RAID controllers, such as the SmartArray 221 and 3200, are supported by Linux out-of-the-box. You can fit up to 6 drives in the front of the 1850R, making it possible to do RAID 5 without buying an external enclosure. I am currently pairing these up with the Proliant Storage System UE, a 4U, and 12-drive external enclosures.

HP now has the 2U "LPr" (a funny choice of name for anyone in the Unix business). I have not actually played with one of these, but they look quite reasonable. Internal RAID would be limited by having only two internal drives, but I wouldn't expect more to fit into this form factor.

IBM has the 1U Netfinity 4000R, which has 2 CPUs, 2 internal disks, 2 ethernet ports, and a PCI slot. I have not actually used these either.

I am most excited about Sun's Netra T1 105. These are very cool: 1 U high, 1 440Mhz CPU, up to 1Gb RAM, up to 32Gb internal disk (2 18Gb drives), 1 PCI slot, and 2 built-in 10/100 Ethernet. Just imagine what you could do with 42 Netras in a single 7' rack! I've paired these up with the 4U A1000 Storage Array, which hold up to 12 drives and can do RAID 5 in hardware.

Sun is also coming out with rack-mountable versions of their departmental servers, which is smart. The previous Enterprise line has some very odd cooling issues that make them hard to rack. The SharkRack company makes some very nice racks and fan trays to handle these servers, but they are pretty pricey.

Compaq uses racks from Rittal, which means they have a vast array of rack components to choose from. I wanted to standardize on a single type of rack, so I looked for a way to mix servers from multiple vendors in a single rack type. I have been happy with the Compaq 7142 rack, but the Sun Netra T1 105 mounting rails are not deep enough for the rack. I found that Compaq sells a kit (Compaq part # CPQ-292406-B21) that allows adjustable depth rails to be mounted inside of the 7142. This means the Compaq rack can have sections of Compaq servers and sections of Sun Netras within the same rack.

Sun Netra T1 105 rails mounted in
Compaq adjustable rail kit.
(Click image to enlarge.)


Pair of Sun Netra T1 105s in Compaq 7142
rack (on right side of LCD panel)
(Click image to enlarge.)

I have not tried mixing other brands of equipment, but I do think the Compaq kit would enable this, as long as your equipment wasn't deeper than the Compaq rack.

As for backups, nearly every one of these platforms has at least wide SCSI for tape devices and 100Mbs for over-network backups to some remote device. Because they all can take two Ethernet connections, you could use the second interface for a separate backup network.

Network wiring is no big deal. I just make custom CAT5 patch cords that run from the servers to the network equipment.

For UPS, I'm using an APC SU2200RMXLNET 2200 VA UPS with one APC SU48RMXLBP add-on battery for every three servers (or external RAID array). Each UPS unit is 5U each, so this combination eats up your U's pretty quickly. Make sure to put the UPS on the bottom, because they are quite heavy.

For PC console mangement, I'm using Connect-Tek 16 port KVM switches with Blac kBox 3-in-1 cables. For the Suns, I'm using Western Telematic serial port switches connected to a dumb terminal (a DEC VT220).

All this adds up to a very heavy cabinet. I am currently mounting them to concrete with "red-top" bolts. I use a rotary hammer drill and vacuum up the dust while drilling. I'm looking at the Hilti powder guns as a less dusty method of installation. I also secure the top of the cabinet to the wall so the server trays can be fully extended for maintenance.

If you are starting to run out of room for your pedestal or desk-side servers and want to move up to a "real" computer room environment, you should explore rack mounting. It may seem hard to justify spending thousands of dollars on inert pieces of metal; but trust me, it's worth it. You can fit amazing amounts of CPU power and disk storage into compact spaces.