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I regret building this $3000 Pi AI cluster

jeffgeerling.com

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Re: I regret building this $3000 Pi AI cluster

#171

Post by LTL_FTC »

mercutio2 wrote: post #122
rogerrogerr wrote: post #102

Earlier quoted context omitted.

100W over a month (rule of thumb 730 hours) is 73kWh. Which is $7.30 at my $0.10/kWh rate, or less than $25 at (what Google told me is) Cali’s average $0.30/kWh.

Your googling gave results that were likely accurate for California 4-5 years ago. My average cost per kWh is about 60 cents. Rates have gone up enormously because the cost of wildfires is falling on ratepayers, not the utility owners. Regulated monopolies are pretty great, aren’t they? Heads I win, tales you lose.

They have definitely increased but not all of California is like this. In the heart of Silicon Valley, Santa Clara, it's about $0.15/kWh. Having Data Centers nearby helps, I suppose.

Re: I regret building this $3000 Pi AI cluster

#172

Post by uncircle »

shermantanktop wrote: post #14
fidotron wrote: post #3

If Pi Clusters were actually cost competitive for performance there would be data centres full of them.

Like the joke about the economists not picking up the $20 bill on the ground? Faith in the perfect efficiency of the free market only works out over the long term. In the short term we have a lot of habits that serve as heuristics for doing a good job most of the time.

> Like the joke about the economists not picking up the $20 bill on the ground?

For those like me that don't know the joke:

Two economists are walking down the street. One of them says “Look, there’s a twenty-dollar bill on the sidewalk!” The other economist says “No there’s not. If there was, someone would have picked it up already.”

Re: I regret building this $3000 Pi AI cluster

#173

Post by ToucanLoucan »

nine_k wrote: post #76
blobbers wrote: post #55

Earlier quoted context omitted.

The internet says 100W idle, so maybe more like $40-50 electricity, depending on where you live could be cheaper could be more expensive. Makes me wonder if I should unplug more stuff when on vacation.

I was surprised to find out that my apartment pulls 80-100W when everything is seemingly down during the night. A tiny light here and there, several displays in sleep mode, a desktop idling (mere 15W, but), a laptop charging, several phones charging, etc, the fridge switches on for a short moment. The many small amounts add up to something considerable.

I got out of the homelab game as I finished my transition from DevOps to Engineering Lead, and it was simply massively overbuilt for what I actually needed. I replaced an ancient Dell R700 series, R500 series, and a couple supermicros with 3 old desktop PCs in rack enclosures and cut my electric bill nearly $90/month.

Fuckin nutty how much juice those things tear through.

Re: I regret building this $3000 Pi AI cluster

#174

Post by kllrnohj »

mattbillenstein wrote: post #154
kllrnohj wrote: post #117

Earlier quoted context omitted.

Note the E5-2690V4 is a 10 year old CPU, they are talking about used servers. You can find those on ebay or whatever as well as stores specializing in that. Depending on where you live, you might even find them free as they are often considered literal ewaste by the companies decommissioning them. It also means it performs like a 10 year old server CPU, so those 28 threads are not exactly worth a lot. The geekbench r…

This is the correct analysis - there's a reason you see this stuff cheap or free. The homelab group on Reddit is full of people who don't understand any of this - they have full racks in their house that could be replaced with one high-end desktop.

> The homelab group on Reddit is full of people who don't understand any of this - they have full racks in their house that could be replaced with one high-end desktop.

A lot of that group is making use of the IO capabilities of these systems to run lots of PCI-E devices & hard drives. There's not exactly a cost-effective modern equivalent for that. If there were cost-effective ways to do something like take a PCI-E 5.0 x2 and turn it into a PCI-E 3.0 x8 that'd be incredible, but there isn't really. So raw PCI-E lane count is significant if you want cheap networking gear or HBAs or whatever, and raw PCI-E lane count is $$$$ if you're buying new.

Also these old systems mean cheap RAM in large, large capacities. Like 128GB RAM to make ZFS or VMs purr is much cheaper to do on these used systems than anything modern.

Re: I regret building this $3000 Pi AI cluster

#175

Post by NordSteve »

dukeyukey wrote: post #144
bunderbunder wrote: post #20

Earlier quoted context omitted.

The cost effective way to do it is in the cloud. Because there's a very good chance you'll learn everything you intended to learn and then get bored with it long before your cloud compute bill reaches the price of a desktop with even fairly modest specs for this purpose.

It's good for the soul to have your cluster running in your home somewhere.

Bad for your power bill though.

Re: I regret building this $3000 Pi AI cluster

#176

Post by phatfish »

buildbot wrote: post #163
kolbe wrote: post #150

Earlier quoted context omitted.

The author, Jeff Geerling, is a very intelligent person. He has more experience with using niche hardware than almost anyone on earth. If he does something, there's usually a good a priori rationale for it.

Jeff is a good person/blogger and does interesting projects but more experience with niche hardware than literally anyone is a stretch. Like what about the people who maintain the alpha/sparc/parisc linux kernels? Or the designers behind idk tilera or tenstorrent hardware.

Youtubers have armies of sycophants (check their video comments if you dare). Not saying they even court them, something to do with video building a stronger parasocial relationship than a text blog I think.

Re: I regret building this $3000 Pi AI cluster

#177

Post by _boffin_ »

Aurornis wrote: post #31
moduspol wrote: post #29

Earlier quoted context omitted.

Also cost effective is to buy used rack mount servers from Amazon. They may be out of warranty but you get a lot more horsepower for your buck, and now your VMs don’t have to be small.

Putting a retired datacenter rack mount server in your house is a great way to learn how unbearably loud a real rack mount datacenter server is.

Not true. Have one running in the closet and never hear it.

Re: I regret building this $3000 Pi AI cluster

#178

Post by geerlingguy »

buildbot wrote: post #163
kolbe wrote: post #150

Earlier quoted context omitted.

The author, Jeff Geerling, is a very intelligent person. He has more experience with using niche hardware than almost anyone on earth. If he does something, there's usually a good a priori rationale for it.

Jeff is a good person/blogger and does interesting projects but more experience with niche hardware than literally anyone is a stretch. Like what about the people who maintain the alpha/sparc/parisc linux kernels? Or the designers behind idk tilera or tenstorrent hardware.

I was just at VCF Midwest this past weekend, and I can assure you I am on some of the lower echelons of people who know about niche hardware.

I do get to see and play with a lot of interesting systems, but for most of them, I only get to go just under surface-level. It's a lot different seeing someone who's reverse engineered every aspect of an IBM PC110, or someone who's restored an entire old mainframe that was in storage for years... or the group of people who built an entire functional telephone exchange with equipment spread over 50 years (including a cell network, a billing system, etc.).

Re: I regret building this $3000 Pi AI cluster

#179

Post by CamperBob2 »

stuxnet79 wrote: post #127
TZubiri wrote: post #115

Earlier quoted context omitted.

Fun fact, a raspberry pi does not have a built in Real Time Clock with its own battery, so it relies on network clocks to keep the time. Another fun fact, the network module of the pi is actually connected to the USB bus, so there's some overhead as well as a throughput limitation. Fun fact, the Pi does not have a power button, relying on software to shut down cleanly. If you lose access to the machine, it's not poss…

> Fun fact, a raspberry pi does not have a built in Real Time Clock with its own battery, so it relies on network clocks to keep the time. > Another fun fact, the network module of the pi is actually connected to the USB bus, so there's some overhead as well as a throughput limitation. > Fun fact, the Pi does not have a power button, relying on software to shut down cleanly. If you lose access to the machine, it's no…

With all these caveats in mind, a raspberry pi seems to be an incredibly poor choice for distributed computing

Exactly. This build sounds like the proverbial "1024 chickens" in Seymour Cray's famous analogy. If nothing else, the communications overhead will eat you alive.

Re: I regret building this $3000 Pi AI cluster

#180

Post by geerlingguy »

TZubiri wrote: post #115
Aurornis wrote: post #17

I thought the conclusion should have been obvious: A cluster of Raspberry Pi units is an expensive nerd indulgence for fun, not an actual pathway to high performance compute. I don’t know if anyone building a Pi cluster actually goes into it thinking it’s going to be a cost effective endeavor, do they? Maybe this is just YouTube-style headline writing spilling over to the blog for the clicks. If your goal is to play…

Fun fact, a raspberry pi does not have a built in Real Time Clock with its own battery, so it relies on network clocks to keep the time. Another fun fact, the network module of the pi is actually connected to the USB bus, so there's some overhead as well as a throughput limitation. Fun fact, the Pi does not have a power button, relying on software to shut down cleanly. If you lose access to the machine, it's not poss…

The Pi 5 / CM5 / Pi 500 series does have a built-in RTC now, though most models require you to buy a separate RTC battery to plug into the RTC battery jack.
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