What to look for in a server rack?

Question

I'm looking to purchase a rack/enclosure for some servers. As this is my first time shopping for this type of equipment, I need to know what to look for. I'm asking not only about how to buy the rack, but also what accessories will I need? What can I do without? What should I look for in terms of delivery and assembly? What do I need to prepare for in terms of power? Cooling inside the cabinet? Anything else I might be overlooking?

I'll share some back story in case anyone finds it helpful, but really generic answers for anyone who is shopping for rack equipment is helpful.

Where I'm at we used to have mainly tower servers... even a number of glorified desktops that lived in our server room. We do have a couple two-poster racks for switches, but everything sits in a wooden bench made of 2x4's and plywood that's been here much longer than I have. Over the last three years I've been able to virtualize the desktop "servers" and as items have come up for refresh I've purchased rackmount servers, with rails. I put the servers on their sides in the old space, and set the rails aside in the store room, biding my time.

We are now (at last!) to the point where in the next six months I'll be down to only a single tower server, and it just happens to be 19 inches high, so I'm thinking 1U shelf. Everything else except the the UPS equipment should mount in a rack. In anticipation of that event, I'm looking to spec out a server rack enclosure to purchase and install this summer. I want to be get preliminary shopping done over the next month or two so I can get it put into the budget for next fiscal year, in time to actually execute the project late this summer.

For size, we should fit comfortably inside a single 42U height-wise, even including mounting our existing switches, so I'm pretty sure one rack will handle it. ... I just need to know what to look for in that rack.

Answer 1

It's really difficult to buy an unsuitable rack today if you're purchasing new.

I usually encounter generic, custom or unbranded racks, APC Netshelter, Dell and HP (10642 G1 and G2 models) in the field. They've all been solid and have handled the systems and equipment I've needed to mount within them.

The basics:

• Begin with your servers. Why not match up with the equipment you're currently using? If you're on Dell servers, you know Dell racks will work. Same for HP. That's a very good starting point.

• In addition to manufacturer compatibility, you'll want a four-post, square-hole rack. At this juncture, you should not consider anything else for housing servers. That means NO round-hole threaded or unthreaded round-hole racks! Other answers here elaborate on the reasons why, but again, it's difficult to end up with a round-hole rack if purchasing something new today.

• Do you want sides and doors? Sides are optional in situations where you make want to bay/bind two similar racks together side-by-side. Also, if you need easy access to systems and cabling, you may want to omit doors/side panels. Is there a security concern or a need to restrict physical access to the systems? If so, the doors and side panels are worth getting.

• Networking gear could mean switches, or switches and patch panels... While both of those work best in 2-post telco or relay racks. They can live happily in a 4-post rack, but would ideally be mounted in the rear rails versus the front of the rack.

• Think about were your infrastructure cabling will terminate. E.g. do you want to drape fixed wiring inside the cabinet? You want to absolutely avoid this scenario.

• You'll want shelves for any non-rackmount equipment (tape drives, Cisco 1700 routers, KVM switches, etc). Try to buy shelves purpose-built for the chosen rack. (e.g. HP shelves with HP racks... APC with APC...)

• I don't usually bother with in-rack cooling. Proper rackmount servers and equipment pull cool air in from the front and exhaust hot air out the rear. A top-mount fan really hasn't been particularly useful in my environments.

• I skip the dedicated KVM/monitor/keyboard in racks these days, opting for a more portable "crash cart" or a laptop-KVM adapter.

• Ensure depth is appropriate for your preferred power distribution choice. APC racks accommodate their PDU's quite well.

• Full rack enclosures are often delivered whole, palletized with casters. There isn't any assembly really required, other than removing them from the pallet anchors. Open-frame racks may be shipped in one or more flat boxes and require assembly.

• Do you want a permanent installation, or do you want casters in the bottom to allow the rack to be moved and repositioned easily?

Outside of those items, you'll be well-served with most recent APC (universally-accepted, very adjustable), HP or even Dell racks. Quite a few data centers use APC racks, or at least use similar designs since they're in the business of accommodating a wide variety of customer equipment. You can also opt for an open-frame 4-post rack if this is a permanent installation.

Rack Solutions is also a great (re)source and can answer any specific questions or give you some design ideas.

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Examples:

Custom rack: Permanent installation. No casters, front view with shelves, side panels and door attached.

HP 10642 G1 rack: Movable rack on casters with side panels installed, door removed, fully loaded with big servers, UPS, CRT monitor (LOLWUT?), KVM, 1U pull-out keyboard/mouse and two shelves.

Dell rack: Rear view. Split rear door for clearance and ease of access (versus a one-hinge full door). Side-mounted cable management loops.

Custom rack: Rear of a custom data center rack enclosure with patch panels and networking facing the rear. Proper clearance for PDU's and server rails.

Open-frame 4-post rack No doors, side panels or casters. A skeleton rack, essentially. Good for airflow or easy access to cabling.

Answer 2

Considering you're upgrading from tables to a rack, you don't need to get too fancy with it.

Accessories:

• Doors, Front Very handy for keeping questing fingers from pressing buttons (or pulling levers) they shouldn't. Also makes for a neater appearance; that can actually count for things! Should be fully perforated, I don't think they're even selling partial-perf doors anymore (thank heavens).
• Doors, Back Very handy for restraining the back-of-rack cable-spam from reaching out and grabbing things. Should also be fully perforated.
• Shelves They make rackmount shelves for holding up things that don't have rails. Sounds like you need one or two of these.
• Fan-tray, top-of-rack Unless you have weird AC, this doesn't sound like the kind of thing you need.
• Fan-tray, back-door At your density, useless overkill. But if you have heat monsters, this can help expedite heat removal more than just the server fans can.
• Monitor tray Usually a 1U or 2U flip-up monitor with keyboard and trackpad/ball. Probably not needed in your area, but useful if space is a problem and you NEED a monitor in your rack somewhere.

If you're going for a back-door, the space between the back rail and the door is going to be where you have to stuff all of your cables and power distribution into. More is better, in my opinion, which is why I prefer longer racks.

Running door-less is just fine, depends on your space, neatness, and how much certain people who pay the bills complain about mess.

Delivery will depend on whether it comes assembled or not, but the few racks I"ve had delivered have actually come in fully assembled on a shipping pallet. This creates some problems. We had to get it off the pallet and roll it on its casters through doors. If the rack is taller than standard door height (80" I believe) getting it through doors will require tipping and other fun things. They're big, heavy and awkward but can be moved around.

Power

Pretty much, unless you're building something new go with what's already in the room. You already have UPSes in there, so connect to them the same way you always have been.

If you're willing to upgrade a few things, going 220v if you're not already is a good idea; PSUs perform a bit more efficiently at the higher voltage. If you're doing that, go for a locking outlet, such an an L6. Then connect up a new 220v UPS to it that also has a locking outlet on it, and connect up a rack-mount PDU, such as one that can connect to the side of the rack, to reduce how far cables have to run to get to power.

The locking outlet thing is where fire-marshals start coming into play, they don't like seeing chained NEMA-15 plugs. Locking plugs mean that the chances of a violent disconnection are greatly reduced, which in turn reduces the chance of a spark being generated. Sparks are ignition sources, and fire-marshals have Opinions about those.

Answer 3

I've used a number of different racks and while they all did the job, some are distinctly better than others.

I strongly recommend staying clear of any rack that uses round mounting holes (I inherited, so it wasn't my choice). Two things stand out for me as really important.

1. The depth. I've had more than one rack where I couldn't fit the rear door because the rack had insufficient depth. If you have the depth and later need to grow, but don't want to buy another rack, you could remount your switches and patch panels in the rear of the rack, freeing up the front.
2. Adjustable pillars. This one might not always be a concern but I've had situations where due to the specific requirements of the installation there were great benefits in being able to reposition the pillars.

All racks I've used, even that oddball with the round holes, can take any number of accessories, such as shelves and fan trays, so don't make such items too high a priority. If the rack manufacturer doesn't have them you can always get them elsewhere.

Above all else, when mounting your servers make sure you use hinged cable trays. Few things annoy me more than the need to unplug or re-route cables so that I can slide the server out.

Answer 4

Others have provided excellent advice on racks.

I want to strongly emphasize that you avoid server racks with round holes, which you probably see with your telecom equipment.

Use racks with square holes. SQUARE! Square holes can accept labor-saving "quickrails" sold by Dell & Supermicro, and rack-nuts can accept just about anything which uses screws. I've racked and re-racked over 400 pieces of equipment in 50 different racks, and I have yet to find any equipment which cannot be racked into a square hole rack. Square holes save labor.

Round holes don't work with a substantial number of rails, and round holes can strip when the wrong screws are used. This leaves you with a useless hole and you might be unable to use that valuable rack space. Rarely, a screw can get stuck in the hole and the equipment will be stuck in the rack. You'll have no choice but to remove the screw with a pair of bolt cutters. Usually you run into this when the equipment is 80% of out the rack and your poor coworker is holding the weight. Sometimes it's 11PM and you're in the server room. Yes, this is are rare. But believe me it happens.

Answer 5

Bottom line, the servers and cables need to fit and still move air. You also need to remember that you will end up moving servers, due to maintenance or just upgrades. So room to move inside is a big plus. I am a fan of the Panduit racks, you can get them extra wide, so all cable management is on the sides of the servers not right behind them like the photos above. A lot of colo's or datacenters don't have very nice racks, as they are maximizing their square footage. When you don't need to worry about that you can end up with a much nicer rack to work in. Round holes are a disaster, as mentioned by the others. Something else to keep in mind, if you put your network patch or switches in the middle of the rack, you will only need 3 & 5 foot cables in the rack - helps with cable management and standardizes what you need to buy.