I'm trying to renew reservations for several older B-series v1 virtual machines, but Bs_v2 isn't available as a resize option. The portal reports "Unsupported hardware." I'm seeing the same behavior in both North Europe and Australia East, including after redeploying the VMs. Is this expected, and what's the safest way to move these machines to Bs_v2 without losing their attached disks?
4 Answers
If these are not Windows workloads, check whether the B-series pricing still makes sense for your use case. Regardless, moving from a SKU with a temporary disk to one without it generally requires recreating the VM or using a migration script that preserves the existing managed disks.
A reservation is primarily a pricing discount, not a guarantee that a particular VM size will have capacity. The resize failure here is more likely caused by the hardware and temporary-disk difference between the two generations. Older B-series v1 machines may need to be migrated to another SKU rather than resized in place.
B-series v1 uses a local temporary disk, while Bs_v2 does not, so this isn’t a normal resize between compatible hardware profiles. The usual migration is to delete the VM while keeping its OS and data disks, then create a new Bs_v2 VM using those existing disks. Be careful to choose the option that leaves the disks intact.
There’s currently a preview feature that may allow this transition directly. Register the VMTempDiskResizePreview feature for the subscription, then try resizing from B-series v1 to Bs_v2 again. The documentation is a bit difficult to find, and this feature is still considered preview, so test it on a noncritical VM first.
You can also leave the network interface in place if you want to preserve its configuration. Just make sure the VM deletion does not remove the disks.