I don’t understand how this is an advantage. Yes, you can swap RAM with the system powered up, but what happens to the information in the module that was removed? Is the OS doing some kind of RAID-like memory allocation? The article wasn’t clear on how this would actually work.
Servers have had memory mirroring as a feature for years. This seems like a cool extension of that technology. It would be an advantage in some systems where scaling out isn’t an option and single node availability needs to be as high as possible.
Apparently, there’s some coordination mechanism, where you tell the OS that you want to remove a certain memory stick, so it moves all the memory onto other RAM sticks (or uses paging to move it to your hard drive). Only then would you actually physically unplug the memory stick.
I guess, you could see it that way…? The important part is that you don’t have to turn off the whole system. It can continue running without interruption. So, the RAM will be lukewarm when you swap it, but the system will still be hot.
I’m curious, does a 3 minutes power down to replace a RAM stick is that much of a deal in enterprise server that they need to invented a whole new technology just for that?
First of all, yeah. In enterprise, 1000 transactions per second can be a requirement. Second, enterprise servers take longer to spool up than 3 minutes.
Many that weren’t based on x86 microcompters could do this: Tandem, I mean, Compaq, I mean HP NonStop machines, Sun Ultra Enterprise as you mentioned, IBM s390 and System-Z, several HPUX systems, I’m sure there’s others.
I remember the ‘good old days’ of Sun Fire 10k and similar servers. You could replace entire boards of CPU and RAM and the server would keep on trucking.
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I don’t understand how this is an advantage. Yes, you can swap RAM with the system powered up, but what happens to the information in the module that was removed? Is the OS doing some kind of RAID-like memory allocation? The article wasn’t clear on how this would actually work.
Servers have had memory mirroring as a feature for years. This seems like a cool extension of that technology. It would be an advantage in some systems where scaling out isn’t an option and single node availability needs to be as high as possible.
Apparently, there’s some coordination mechanism, where you tell the OS that you want to remove a certain memory stick, so it moves all the memory onto other RAM sticks (or uses paging to move it to your hard drive). Only then would you actually physically unplug the memory stick.
See, for example: https://docs.kernel.org/admin-guide/mm/memory-hotplug.html
(Mind that this is kernel documentation. If you actually want to do this, there’s probably some CLI program to make it easier.)
Then it’s not Hot Swap, just Lukewarm Swap?
I guess, you could see it that way…? The important part is that you don’t have to turn off the whole system. It can continue running without interruption. So, the RAM will be lukewarm when you swap it, but the system will still be hot.
So “warm plugging” is a thing - it means a piece of hardware is detachable while the machine is asleep.
If you really want to be pedantic you could setup raid 1+0 or 5 and live the true RAM hot swapping life
USB devices are also hotpluggable, but that doesn’t mean that the data stays in the system if you just pull out the HDD.
But the ram will loose it without being powered.
This would either require persistent memory or something that could cache the flash for some minutes.
Cool, but why?
Enterprise server use mainly, to minimize downtime, which is a huge deal there. On the consumer level it doesn’t have much purpose.
I’m curious, does a 3 minutes power down to replace a RAM stick is that much of a deal in enterprise server that they need to invented a whole new technology just for that?
Have you ever power cycled a server? It can take over 10 minutes depending on the machine.
yeah.
The hangup is that you think shutting down and restarting a server takes 3 minutes
The surplus enterprise hardware I have in my homelab takes 3 minutes to just get to BIOS
Depending on your SLA, 3 minutes can be a pretty big chunk of your monthly error budget.
First of all, yeah. In enterprise, 1000 transactions per second can be a requirement. Second, enterprise servers take longer to spool up than 3 minutes.
Yes. Server boot times are long. Enterprise level NICs and hard drive controllers do a lot of checking at startup.
Historically, there were Sun servers that could hot swap CPUs. X86 can’t do that, though.
Many that weren’t based on x86 microcompters could do this: Tandem, I mean, Compaq, I mean HP NonStop machines, Sun Ultra Enterprise as you mentioned, IBM s390 and System-Z, several HPUX systems, I’m sure there’s others.
The coveted 5 9s of availability is only 5.26 minutes of downtime
5.26 minutes per year*
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I remember the ‘good old days’ of Sun Fire 10k and similar servers. You could replace entire boards of CPU and RAM and the server would keep on trucking.
Don’t. I still miss Sun. I miss that “Hey, fuck MS Office’s crazy pricing. Let’s buy their competitor for less and open source it!” energy.
We need more of that in these times.
I remap Caps Lock to Ctrl to this day as that’s where it’s meant to be, god damn it!
IBM System-Z mainframes still support CPU hot-swapping AFAIK.
Excellent! Hot swap all the things!!!
FInally, Banjo Tooie on PC
Did anyone else notice that in their stock photo they’re trying to put the DIMM into the socket backwards?
You want that distinct crunch as you force the RAM in with a mallet
Every stock photos is like a mini Easter eggs hunt.
Meanwhile, Windows requires you to buy a new license if you change your mouse.
That’s not entirely true. You can get a universal mouse license that will cover up to twenty approved mouse changes.