I'm working on a home project to build a VM server. I'm have older hardware (IBM x306) and my processor doesn't have built-in virtualization support, so I'm going with VirtualBox. That seems to give me the most flexibility with supported guest OS's on my P4 processor. I'm using CentOS 5.4 installed on a software RAID1 array and I ran into an issue where every time I try to create a fixed-size virtual hard drive my whole server locks up. I think VirtualBox may have a problem managing virtual hard drives on a software RAID (unconfirmed).
Anyway my idea is to create 2 mirrored volumes using LVM to see if that works out any better. I started reading up on it and found
this article. My server only has 2 hard drive bays (it's 1U) and the article says that 3 physical disks are really necessary for true fault tolerance.
Quote:
Quote:
LVM mirroring at a minimum requires three physical volumes:
1. A volume for one side of the mirror
2. A volume for other side of the mirror
3. A volume for the log
Note: We recommend for recoverability purposes that the PV's be three separate physical disks. Although not recommended, the PV's could also be a combination of partitions from one more physical disks but understand that a hardware failure could render the data on the LVM mirror useless - which somewhat defeats the purpose of LVM mirroring.
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So, it sounds like if I create a standard 100MB /boot partition and then save some space on a drive for the LVM log and then one of my drives goes, I will not be able to insert a replacement, rebuild my mirror and resume normal use since the log and/or the /boot partition could be lost. Since it isn't possible to install 3 physical drives on my machine, I came up with this strategy to achieve the highest level of fault tolerance.
Code:
Disk1 Disk2
_________________ ________________
|________________| <-- /boot (software RAID1) --> |________________|
|________________| <-- Volume for LVM log (software RAID1) --> |________________|
| | | |
|Logical Volume 1| LV1 and LV2 mirrored |Logical Volume 2|
|________________| using LVM (not RAID) |________________|
That way there is a mirrored copy of the LVM log and the /boot partition on each drive. If one fails, I could put in a new drive, resync the RAID1 partitions to it, and then rebuild the LVM mirror. Does this make sense? Has anyone heard of this configuration being used? Are there any glaring issues that might prevent it?
