Linux server consolidation: Xen, Software RAID, LVM2

I play with virtual machines all the time but I don’t actually have any that are part of my daily “critical infrastructure,” in the sense that our important file, web, and backup servers are all running Linux on bare metal. I’m now coming at this from a security-conscious administrator’s and cheapskate’s perspective.

Some rough requirements:

  • I want to use mirrored disks so that the failure of one drive won’t bring the whole thing down.
  • I want the RAID configuration to TELL ME when one disk fails so that I know to replace it before the next one fails.
  • I want to be able to relatively painlessly allocate disk space between different VMs.
  • I’m not terribly concerned with performance at the moment, as the live servers are not very heavily loaded and the backup servers run on a schedule in the middle of the night.
  • I don’t want to spend any money on software.
  • I don’t want to be forced to use Windows to manage the thing.

I went into this thinking that VMware’s free ESXi would do the trick. However, I’ll either need to manage it from Windows or learn all the necessary command line mechanisms. I’m also approaching this from the “my brain is full” perspective, so I’d rather not add complexity I don’t need. I do have a fancy SAS/SATA RAID card available if need be, but I don’t want to fuss about drivers for it.

So, at the moment I’m leaning towards Xen. It seems like Xen vs KVM is a hot debate, but I can use paravirtualized guests and it seems that paravirtualized Linux on Xen is regarded as having the highest performance.

I haven’t actually put the thing together yet so there is likely to be another post. Pending the availability of free time I may try to mature this into a useful guide, since in my opinion much of the information available about these technologies (and a lot of Linux sysadmin stuff, for that matter) is rather dated.

Here are some threads and references that I have found to be useful:

Very useful Gentoo thread on LVM pros & cons

Very useful Debian thread on degraded software RAID array

Very useful Ubuntu thread on VMware ESXi vs VMware Server

Very useful guide to a particular installation of Xen using several large disk drives (PDF)

Xen with Ubuntu 8.04 LTS and software RAID, LVM

Ubuntu 8.04 LTS as a domU on the above setup

Software RAID1, Debian Sarge fresh installation, kernel 2.6.8, GRUB. A little dated, but not as dated as a lot of the other docs. It is kernel 2.6-based.

The RAID controller that I have available is an Adaptec SAS-3405. This page and these scripts appear to be somewhat useful regarding its use from Linux. About 2 years ago I tried to use that card with VMware ESX server 3.0.x to no avail. Here is a thread about it.

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