It sure would make life a lot easier if the data centers we manage existed entirely within two dimensions; which seems to be the world that server manufacturers think we live in. To them, the only two specifications of size that matter are height and width. They could care less about that forgotten dimension, DEPTH.
Every time a new server appears on the market the very first spec I check is depth. Width is a given, and heights are limited to a very narrow range (1U, 2U, etc), but the makers of gear destined for the data center seem to think they’ve been given a free pass go as deep as they please. This drives me and I can only assume my peers in the community, crazy! Nothing would please me more than to get a bunch of Dell, IBM, HP, Apple, etc server hardware engineers into a room … and then flood it with Halon. Oh, OK maybe not halon… I’d probably hit them with FM200 and then when they come to take them for a tour of a data center and show them the error of their ways.
My biggest beef here is the 1U servers that seem to be growing to absurd depths. The worst offenders I’m dealing with at the moment are Dell’s 1950 and Apple’s latest version of the Xserve. Both arrive at 30″ (76.2cm) or longer. I’m sure there are others that have reached these lengths too. They have roughly the same form factor as the flight deck of an aircraft carrier. 1U x ~18″ x REEEEAAAAALLLLLLLYYYYY LOOOOOOONG. Attach a catapult and you could be launching Maverick and Iceman in their Tomcats to intercept the inbound bogeys.
When 1U servers started appearing they were rather compact, akin in form factor to your average Ethernet switch. 1U x ~18″ x ~12″. Some, such as the old Cobalt “RAQ” web servers (remember those?) could be stacked on both sides of a 2-post rack for a total of 84 servers in under 6sq’ of floor space. When the larger players started shipping 1U boxes, they ranged in depth from 20″ to 24″ (51cm - 61cm) on average. This was the same, or a bit longer than the average 2U and 4U boxes that preceded them, but still manageable. They could fit in 2-post or 4-post racks. But about five years ago 1U servers started getting longer and longer.
How does this affect us? Density of course. While having nothing but 1U servers would seem to be a step towards higher density that is really only true if you live in a two-dimensional world. If your servers are now over twice as deep as they once were entire rows of datacenters have to be moved farther apart to accommodate them. Logically if your rows of racks are farther apart, the number of racks you can install in your datacenter shrinks.
Additionally cabinets keep getting deeper to accommodate these longer and longer servers. It used to be that any server could be mounted in a 2-post rack. Cabinets were only needed if extra security was desired. Now the manufacturers of server EXPECT you to mount them inside cabinets. No flexibility in mounting is offered… except maybe cage nuts or tapped.
I remember when a cabinet averaged 32″ (81cm) deep. Many of today’s servers won’t even fit in a 32″ deep cabinet. Well, they might fit, but you won’t be able to close the doors anymore! The cabinets we’re buying for our data center are now 42″ (107cm) deep. That adds almost two feet (61 cm) to every aisle in the facility. That means you can fit fewer aisles. By my top-of-my-head math that means you lose two full aisles for every 5000 sq’ of data center. Depending on the number of racks-per-aisle, that can add up to a LOT of servers you lose by having these outrageously long boxes.
There are many facilities, primarily older colocation datacenters that limit how much power-per-rack you can use, so frequently you see 42U cabinets with MAYBE 14U of space that is usable. Why even bother with 1U servers then? Your cooling is messed up by all the empty space. You might as well go back to the big 4U servers of yesteryear and pack ‘em in. But nobody makes those anymore. The only time you see servers larger than 1U is when they are serious power hogs, packed with drives and CPU. So we’re back to square one.
Two recent events triggered this rant:
A customer sent a new Apple Xserve to us to replace their old Apple Xserve. The old one was a G5 unit, the new one a Dual-Core Xeon unit. Both we and the customer thought this would be an easy swap… power down, unplug, and pull out the old one, slide in the new one plug in and power up. Minimal downtime. Unfortunately the new one is two inches longer, the ports (network and power) have swapped sides, and the rack mounting hardware is completely different. What should have been a 5 minute operation turned into a multi-hour ordeal.
The next event, which sent me over the top is a new client had 32 Dell 1950’s shipped to our facility, along with an APC Netshelter cabinet and powerstrips to plug it all in. Upon arriving for assembly we noted that the rackmounting rails provided by Dell stuck out in the back of the 32″ (81cm) deep 1950 by an additional 3″ (7.6cm). So now the total depth of the servers amounted to 35″ (89cm). There was no longer enough room at the back of the cabinet to mount the power strips. Comparing these to previously installed Dell 1950 servers they did not have rails this long. What does this mean? Is Dell planning on making their next rackmount servers even LONGER? How long before we see 36″ long servers?
Do server designers ever try to actually rackmount their gear? Do they account for cables, power strips, etc? It seems to me that the unrestricted lengthening of the standard 1U server is becoming completely counter-productive to the original design goal of the 1U server, namely density of computing in the minimum amount of space. They’ve gained rackspace at the expense of usable FLOOR space. In the balance sheet of datacenter operations floor space is WAY more expensive than rackspace. I want my floor space back.
Does this frustrate you as much as it frustrates me?
