Re: Using blockdev-mirror for Live Backup

[Alberto Garcia]

On Tue, May 16, 2023 at 11:58:30PM +0330, aliqrudi@gmail.com wrote:

> We are executing hundreds of VMs in our hosts (dual AMD EPYC 7002
> CPUs + 2TB memory + 8 NVMe disks).  To cope with disk failures, we
> tried different Linux software RAID mechanisms.  At high disk usage,
> all of them faced unexpectedly high CPU load, mostly in the kernel.
> Therefore we decided not to use software RAID.

An alternative is the Quorum block driver:

   -drive if=virtio,driver=quorum,
          children.0.file.filename=disk0.qcow2,
          children.1.file.filename=disk1.qcow2,
          children.2.file.filename=disk2.qcow2,
          vote-threshold=2

   (this is supposed to go all in one line)

This is similar to RAID-1, but note that the disk images themselves
do not contain any kind of additional metadata and they don't know
that they are part of a Quorum array, it's your responsibility to put
identical images together.

Regards,

Berto