Live-resizing vCPU, RAM, and disk
How online resize works on Vintony, and when to take a snapshot anyway.
3 min read
Live resize on Vintony VPS instances is genuinely live — sub-second pause for vCPU and RAM, no pause for online disk grow. Here's what happens under the hood and when you should still snapshot first.
vCPU hotplug uses QEMU's CPU-hotplug API. The new vCPU appears in the guest's `/sys/devices/system/cpu/cpuX/` tree within a second; for older kernels you may need to `echo 1 > online` to activate it.
RAM uses virtio-mem to plug or unplug memory regions. Going up is unconditional; going down requires the guest to release pages first, which we accomplish via a small kernel module on our default images.
Disk grow uses LVM online thinpool extension followed by an ext4/xfs filesystem grow. The whole operation is online; no maintenance window required.
When to snapshot anyway: any cross-plan family move (e.g. EPYC → Xeon, which may change available instruction sets), any disk shrink, or any migration into a different region. A snapshot costs two seconds and a few cents; the undo button is worth it.