3 ms·

I'm not sure hotpugging is still there.

by wmf 2y ago

deleted 2y ago
[deleted]
chiph 2y ago
At least partially - the technical introduction for the Z17 says that several items can be concurrently maintained (IBM-speak for hot-swapped). So far as major items like the processing units - maybe (still reading). (3.4mb PDF) https://www.redbooks.ibm.com/redbooks/pdfs/sg248580.pdf https://www.redbooks.ibm.com/redbooks/pdfs/sg248580.pdf > Four Power Supply Units (PSUs) that provide power to the CPC drawer and are accessible from the rear. Loss of one PSU leaves enough power to satisfy the power requirements of the entire drawer. The PSUs can be concurrently maintained I would think their customers would demand zero downtime. And hey - if BeOS could power down CPUs almost 30 years ago I would expect a modern mainframe to be able to do it.
- wmf 2y ago
  All servers have hot-swap power supplies. (I'm pretty sure BeOS never actually powered off CPUs; it just didn't schedule anything. Linux "hotplug" works the same way today.)
sillywalk 2y ago
The Unisys Clearpath/MCP runs on Xeons, so I don't think there is CPU hot-swapping. I don't know about physically removing a drawer, but on IBM Z, if there is a un-recoverable processor error, it will be shut down, and another spare processor brought on-line to take over, transparently. I don't know how licensing/costs ties into the CPU/RAM spares.
- skissane 2y ago
  > The Unisys Clearpath/MCP runs on Xeons, so I don't think there is CPU hot-swapping. Nowadays it is a software emulator that runs under Linux – so if the Linux kernel and hardware you are running it on supports CPU hot-swap, then the underlying OS will. I believe at one point Unisys would only let you run it on their own branded x86 servers, they now let people run it in Azure, and I'm sure Microsoft isn't using Unisys hardware for that. Running Linux in a VM, the hypervisor can implement hotplug whether or not the underlying server hardware physically does. Of course, without physical CPU hot-swap, it may not add much to reliability, but it still can potentially help with scaling. If you hotplug a new virtual CPU into the Linux VM, you'd probably want to hotplug another emulated mainframe CPU into the mainframe CPU emulator at the same time. No idea if Unisys actually supports that, but they easily could, it is just software – the Linux kernel sends a udev event to userspace when CPUs are plugged/unplugged, and you could use that to propagate the same event into the mainframe emulator.
yencabulator 2y ago
> With IBM z17 ME1, concurrent upgrades are available for central processors (CPs), Integrated Facilities for Linux (IFLs), Integrated Coupling Facilities (ICFs), and IBM Z Integrated Information Processors (zIIPs). However, concurrent PU upgrades require that more PUs are physically installed but not activated previously. > In the rare event of a PU failure, one of the spare PUs is immediately and transparently activated and assigned the characteristics of the failing PU. Two spare PUs are always available on an IBM z17 ME1. PU = Processor Unit, a common name for the CP/IFL/etc variants above. So, you can tolerate minimum 2 CPU failures (money gets more) without shutting down. Beyond that, you can move active workloads transparently to a (possibly remote) zSeries, to schedule maintenance.

I'm not sure hotpugging is still there.

by wmf 2y ago

I'm not sure hotpugging is still there.

deleted 2y ago

[deleted]

chiph 2y ago

At least partially - the technical introduction for the Z17 says that several items can be concurrently maintained (IBM-speak for hot-swapped). So far as major items like the processing units - maybe (still reading). (3.4mb PDF) https://www.redbooks.ibm.com/redbooks/pdfs/sg248580.pdf https://www.redbooks.ibm.com/redbooks/pdfs/sg248580.pdf > Four Power Supply Units (PSUs) that provide power to the CPC drawer and are accessible from the rear. Loss of one PSU leaves enough power to satisfy the power requirements of the entire drawer. The PSUs can be concurrently maintained I would think their customers would demand zero downtime. And hey - if BeOS could power down CPUs almost 30 years ago I would expect a modern mainframe to be able to do it.

wmf 2y ago
All servers have hot-swap power supplies. (I'm pretty sure BeOS never actually powered off CPUs; it just didn't schedule anything. Linux "hotplug" works the same way today.)

sillywalk 2y ago

The Unisys Clearpath/MCP runs on Xeons, so I don't think there is CPU hot-swapping. I don't know about physically removing a drawer, but on IBM Z, if there is a un-recoverable processor error, it will be shut down, and another spare processor brought on-line to take over, transparently. I don't know how licensing/costs ties into the CPU/RAM spares.

skissane 2y ago
> The Unisys Clearpath/MCP runs on Xeons, so I don't think there is CPU hot-swapping. Nowadays it is a software emulator that runs under Linux – so if the Linux kernel and hardware you are running it on supports CPU hot-swap, then the underlying OS will. I believe at one point Unisys would only let you run it on their own branded x86 servers, they now let people run it in Azure, and I'm sure Microsoft isn't using Unisys hardware for that. Running Linux in a VM, the hypervisor can implement hotplug whether or not the underlying server hardware physically does. Of course, without physical CPU hot-swap, it may not add much to reliability, but it still can potentially help with scaling. If you hotplug a new virtual CPU into the Linux VM, you'd probably want to hotplug another emulated mainframe CPU into the mainframe CPU emulator at the same time. No idea if Unisys actually supports that, but they easily could, it is just software – the Linux kernel sends a udev event to userspace when CPUs are plugged/unplugged, and you could use that to propagate the same event into the mainframe emulator.

yencabulator 2y ago

> With IBM z17 ME1, concurrent upgrades are available for central processors (CPs), Integrated Facilities for Linux (IFLs), Integrated Coupling Facilities (ICFs), and IBM Z Integrated Information Processors (zIIPs). However, concurrent PU upgrades require that more PUs are physically installed but not activated previously. > In the rare event of a PU failure, one of the spare PUs is immediately and transparently activated and assigned the characteristics of the failing PU. Two spare PUs are always available on an IBM z17 ME1. PU = Processor Unit, a common name for the CP/IFL/etc variants above. So, you can tolerate minimum 2 CPU failures (money gets more) without shutting down. Beyond that, you can move active workloads transparently to a (possibly remote) zSeries, to schedule maintenance.