Making Best Use of Data Center Space: Density Vs. Isolation
jfruh writes The ability to cram multiple virtual servers on a single physical computer is tempting — so tempting that many shops overlook the downsides of having so many important systems subject to a single point of physical failure. But how can you isolate your servers physically but still take up less room? Matthew Mobrea takes a look at the options, including new server platforms that offer what he calls "dense isolation."
Man buys 1/3 rack and fills it. Looks for faster servers.
I read the blog post, and he's just comparing having a beefy server with multiple VMs to instead having a bunch of blade servers. How is this new? Heck, 13 years ago at a Canadian federal government job we swapped our web servers for blades.
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Personally I keep eyeballing the SuperMicro TWIN line. Extremely dense configurations of multiple servers per unit. Spread the workload across multiple physical boxes. Use something like vCenter Server to manage the networking and other resource configurations to simplify making them all the same and adding easy of migrating VMs from one physical host to another.
Because he writes like he is.
You should have your VM images on some storage system like a NetApp, this lets you transfer the entire VM to another blade if one fails. So you have two blade racks both connected to the NetApp with software set up to fail over all the VM's from a failed blade to a blade on the second blade rack. You would probably run all the blades active on 1/2 load where on failure you transfer to the alternate blade on the 2nd rack and go to a full load on that blade. This protects you from a rack failure as well as an individual blade failure. The router/hub on a blade server is a single point of failure which is why you need 2 racks.
is not good.
The problem with slashdot is that most of its users were bullied and stuffed into lockers as kids!
Maybe TFA just skipped it for brevity; but 'number of boxes' seems like a poor model for judging risk of failure. Some components appear to be nearly immortal(yes, mainframe wizards with onions on their belt have told me tales of failed CPUs; but it always seems to be PSUs, disks, and RAM that provide a daily stack of RMA boxes for the fedex guy).
Given that, in a situation where I have less money than would be ideal, I want to know which parts are critical to a dangerous number of systems(especially ones that VM migration doesn't hide well), not how many individual computers with their own boot screen and memory space I have.
In the case of the setup in TFA, the storage system is what scares me. That sucker goes down and every VM on an iSCSI LUN goes down screaming. And storage appliances are basically just servers; but with more exposure to HDDs being awful. Why fret about how many VM servers you have(as long as it's at least enough that you can reshuffle if one goes down) when your storage system is just waiting to knife you in the back and twist?
Also, how is your switching looking? Not much extra credit for still having VM nodes if you can't reach them, migrate to them, or supply th with storage.
Put all your eggs in one basket.
Then make sure you have copies of that basket.
If you're really worried, put half the eggs in one basket and half in another.
We need an article for this?
Hyper-V High Availability Cluster. It's right there in Windows Server. Other OS's have similar capabilities.
Virtualise everything (there are a lot more advantages than mere consolidation - you have to LOVE the boot-time on a VM server as it doesn't have to mess about in the BIOS or spin up the disks from their BIOS-compatible modes, etc.), then make sure you replicate that to your failover sites / hardware.
Look at the likes of HP Moonshot and AMD Seamicro. Those are some nice toys to play with ...
Nor are they "isolated". All of the blades connect to the same backplane.
And moving VM's between individual blades is a hassle unless you use some form of shared storage. Which makes them even less "isolated" but more redundant.
This reads more like he just wanted to show off that he calls blade servers "dense isolation".
VM is not magic. Also look into "fail over".
If you have to be called in to replace a CPU at 4 am then you have not planned correctly.
At most places I've worked, the situation described was requested / imposed by the PHBs and bean counters to save costs, reliability and isolation be damned.
Lack of physical room was NEVER, I repeat, NEVER an issue. This ain't Tokyo we´re talking about. If your office building doesn't have a spare room, you'll have other major issues down the road when ytour company expands its business.
Isn't it easier just to rent some dedicated boxes somewhere like Hetzner if you want dedicated hardware?
I'll accept the idea that somewhere somebody has so many servers and so little space that a blade center was the only way they could achieve the density they needed.
Except I've never seen it -- all the blade centers I've ever seen have been partially full and the equivilent 1U and 2U servers probably would have fit in the same or less space than the blade chasis was occupying.
And almost always there's a mongolian clusterfuck when they decide to add blades to the chasis -- which they inevitably do, because they have so much money sunk into the blades that there's no way out from under it.
The mongolian clusterfuck is the result of the byzantine cofiguration rules each vendor has for determining a blade's NIC or FC mapping with the blade center's (overpriced) internal switch bays. Half or full height? LoM or mezzanine slot? Which mez slot? Which blade slot? Oh, you want an extra NIC on that blade? Sorry, the mapping requires an additional switching module which will cost you more than any decent L3 48 port gig switch.
Whatever the savings from the blade center (and maybe in some metered situation there is power savings of couple hundred watts) is easily lost in hours of troubleshooting when trying to do something different.
Blade centers always look like some kind of pre-virtualization version of server consolidation that became obsolete once 24U of servers could easily be run on 8U or less of VM host and SAN. They would be a lot more interesting if their mapping regeimes weren't hard wired -- blade advocates give me blahblah "point of failure" about a switchable/configurable backplane.
...that's why you have multiple VM hosts....when one physically fails, the VMs transition to another physical host...it's not difficult.
He mentions just one product, while ignoring a host of other offerings.
virtualize means software runs on this hardware. this is a tight coupling. If containers (Docker is one such container with lots of hype= think quota based process) take off then it may be better to get a sea of computes and aggregate them. Then have your processes run n of them on this (one region...or many). That way failures happen and the orchestration layer above the containers can react and run or more of the process when things get busy or fail. Consider reading about mesos (it's what twitter uses to get scheduled work computed in a fault tolerant manner). https://mesosphere.github.io/marathon/docs/native-docker.html (here is a link with marathon directing the mesos layer with Docker containers.
In the current US situation at least, you have room to move servers from figurative jails to real ones.
Using virtualization correctly is NOT a single point of failure. Using individual servers for individual tasks is.
We have some Cisco UCS blade systems that are part of our VCE vBlock. 5 chassis with 40 blades. 32 of them running ESX, 6 running physical SQL (two 3 node MS clusters) and 2 blades sitting there doing nothing but acting as spares. All of the ESX and SQL servers boot from the SAN, there are no disks in the blades. Adding additional chassis and blades is very easy. At least compared to adding 8 more physical servers.
In theory I guess we could have done what we did in the past and use 40 single 1U servers and boot from SAN and accomplished almost the same thing but that would be about 250-275 more ethernet cables, 80 power cords, and 80 FC cables so a hell of a lot more ports and cabling would have been required.
The vBlock concept is nice. It is very structured but still flexible. We go through twice a year with patches and upgrades. We upgrade every single module, piece of firmware, VMware, switches, the SAN, fiber switches, all multipathing, bios, etc on the whole entire system in about 24 hours in a very logical step by step manner. Anyone can do that even without a vBlock but when you have 4 engineers supporting 20 offices around the world (operational and engineering), having that "structure" of the vBlock takes a huge load off your back.
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