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It might sound as "how long is a piece of string"? In my current job the process is to leave 1U spacing, with no blinders, between servers; this incurs a considerable loss of space, no event sparking about turbulent air flow. Everyone is adamant that's the way to go and I have hard time making my case for a no spacing approach to rack-filling. What's your experience? Provided that the AC air flow is fine and tile floor robust, how many hp servers have you managed to put into a 42U rack?

I'd love to have hp official recommendations, if anyone has a link to share.

Thank you, -A Ps: google search didn't really give usefull info...

ewwhite
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Alex
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4 Answers4

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You can fill a 42U rack with ProLiant servers as long as you have the power distribution and cooling coverage to support it. Cold air is drawn-in from the front and exhausted out the rear of the chassis. ProLiant servers have a high thermal tolerance and this is a supported setup.

Reasons for leaving space/blank panels can include aesthetics, ease of maintenance, cabling, etc... but there's no harm in stacking the systems.

Also see: Rack Mounting a Server with hot air vents on the top? where I give an example using G7 ProLiants.

Community
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ewwhite
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  • Precisely... But that doesn't seem to convince anyone here. It's up to the point where they think that stacking the servers will prevent proper heat dissipation. I think they just need something like a white paper to cover their ass. – Alex Jun 20 '12 at 17:37
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    Get HP sales involved, they'll help you if they know there's an order in the pipeline. – Chopper3 Jun 20 '12 at 17:42
  • Get your HP rep to find you a whitepaper or an expert. – mfinni Jun 20 '12 at 17:42
  • Jinx! (10 more chars) – mfinni Jun 20 '12 at 17:43
  • Ok, that's exactly what the guys here say. The top-vent lead everyone to think that there must be spacing, which I think is incorrect. Until I get an official hp recommendation that's not going to change. Did you get your hands on such document? – Alex Jun 20 '12 at 17:44
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    Email your HP sales guys, say "Could you provide pricing for a single 43U rack filled with 42 x DL360's including support please", when they send in the quote you have your answer as their quotes have to be signed off by technical presales. – Chopper3 Jun 20 '12 at 17:47
  • The vent is passive ventilation for the PCIe slots on the DL360 G7. The *DL380 G7*, for instance, does not have such vents. – ewwhite Jun 20 '12 at 17:47
  • I'd love to have the hp guy, but it's controlled by another department, so no account number available. Plus the guy who makes the company recommendation just doesn't want to hear anything about it(20 years experience ossified in his job).... – Alex Jun 20 '12 at 17:50
  • Then check on the [HP support forums](http://h30499.www3.hp.com/t5/Planning/HP-DL360G7-server-rack-mounting-without-skipping-a-gap-between/td-p/5499735#.T-INHytYvYA) to get an expert answer. – ewwhite Jun 20 '12 at 17:52
  • I have a dedicated HP sale team, I'll drop them a line but they may take a while. Oh and I meant 42U above, typo! – Chopper3 Jun 20 '12 at 17:56
  • @Chopper3 : that would be almost a god send! :) – Alex Jun 20 '12 at 18:33
  • Sent the email, it's 19:30pm in the UK, I'll let you know what they say. It's 'godsend' btw ;) – Chopper3 Jun 20 '12 at 18:36
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    Right Alex, only just got an official word back. The WILL work stacked on top of each other BUT 'best practice' is to leave a gap - you you/me AND your colleagues are both right and wrong. Sorry this doesn't conclusively answer your question but the key part is they WILL support 42 1U servers in a rack, they might just moan about it not being 'best practice'. – Chopper3 Jun 21 '12 at 17:57
  • @chopper3 Did they give a reason for needing/wanting the gap? – ewwhite Jun 21 '12 at 18:16
  • No, just 'best practice' - quite surprised myself. – Chopper3 Jun 21 '12 at 18:32
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    Yeah - like I say though, what they support and what they write in a 'best practices' are very different things. – Chopper3 Jun 22 '12 at 14:19
  • @Chopper3: woo, this is really surprising, considering that the immediate consequence is to double a server deployment footprint. Collocation turns very expensive this way. My 20-year-old-experienced-ossified colleague will smile... Damnit. I just can't figure out why they say this? Not even speaking about the number of racks I've seen in previous jobs with servers stacked on one another. plus, if you have to use blanking panels, what's the point of leaving a gap? This leaves a layer of hot air that's never cooled properly. Not the answer I wanted, but it is what it is.. Thanks a bunch! – Alex Jun 22 '12 at 14:37
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If you have the power outlets and cooling capacity you can fill a 42U rack with 42 of those servers, I've seen it done - and HP will support it - but to be honest it was needlessly heavy and was replaced by blades very quickly afterwards - would that be an option, or SL's for that matter.

Obviously in your case you're limited to 22.

Chopper3
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  • True, it's always good to leave up to 4u spacing at the bottom for the cable slack etc.. – Alex Jun 20 '12 at 17:54
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Get blades if you are worried about space.

Ladadadada
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fern
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    The specific requirement for HP DL360 G7s suggests that the hardware might have already been purchased before the question was asked. It was asked a bit over a year ago so new answers are unlikely to be helpful. – Ladadadada Aug 06 '13 at 09:39
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The 1U vertical air gap between servers is reputable to stop the server below adding extra heat to the server above. Any its also best practise to put blanking plates on these gaps. So that the cool air in the front passes more efficiently through the server.

As for this 1U vertical gap, I've never seen any supporting material, so Ill take it with a pinch of salt and would be happy to forget it if research disproved this hypothesis. Its a moot point at our place as we couldnt power a full rack.

Sirch
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  • I strongly dispute this answer - HP specifically states that they support racks FULL of servers and that no spacing is required. In fact not only do they sell fully built rack completely full of servers with no gaps but I've bought a few like this. The spend a huge amount of time ensuring that all heat is vented rearwards to allow them to do this - other brands may not and thus may have this restriction. – Chopper3 Aug 06 '13 at 09:59
  • You dispute that some manufactures say leave a gap? I've heard it plenty, and when I pushed the for a why, I was told that. Perhaps you could ask why too. I'd like to see best practise be based on research too. – Sirch Aug 06 '13 at 10:03
  • Not at all - I dispute that HP say to leave a gap. As I state some servers aren't as well designed so probably do leak heat upwards - HP specifically design theirs not to - but this question is about a particular HP model that does support 42 servers in a 42U rack as detailed in their documentation. – Chopper3 Aug 06 '13 at 10:06
  • I dispute it too, I've been long enough in telco shelters to say that filling up the full 42 U should be fine, provided there's a proper cooling system, and power capacity. I think the HP sales guy just didn't want to deal with an installation lacking adequate cooling system. Spacing at the bottom/middle is required to accomodate the cable slack, end up with 34 to 38 U used, that's all. But there is no reason in the world to impose 1U spacing, considering this doubles the hostings costs. Dell provides 42U support with similar server cooling design, HP sales are just sissies. – Alex Aug 07 '13 at 13:50