Linux – KVM Host: Hardware RAID with cache + BBU vs. Linux Software RAID with LVM writeback cache and UPS


I want to set up a RAID 5 with 3x1TB drives on a Linux KVM-Host. The RAID will be used as LVM thin storage for VM disks.

There has already been much discussion on hardware raid vs software [1]. According to this discussion one should not use software raid but hardware raid with cache and BBU for VM disk storage because of the better write performance.

What I would like to know is if the following setup would be comparable to a hardware raid with cache and BBU (e.g. HP P410 512 MB + BBU) in terms of read/write performance and data safety:

  • Linux Software RAID / mdadm RAID 5
  • LVM writeback cache on a 512 MB ram disk
  • Host backed by UPS to prevent data loss like the BBU on hw raid

[1] Software vs hardware RAID performance and cache usage

Best Answer

None from above! You really need to look at ZFS on Linux.

Perfect discussion, tons of links.