[linux-lvm] Hot backup for boot/root disk

[linux-lvm] Hot backup for boot/root disk

[Hacksaw]

I have a Linux system with 2 identical disks for the OS portion. The 
goal is to have them essentially mirrored, but not continuously. I want 
to be able to rsync them on occasion.

I need this disk to be bootable on a moments notice, in case the main 
one dies.

The layout of the current boot disk is a partition for /boot which is 
ext3, and then the rest as a LVM set, of essentially one large partition.

My first thought is to create the second disk pretty much as the first 
was created, do the rsyncs, and make some script that will maintain the 
configuration files which mention the physical disks.

I have to admit that it's unclear what they all are.

In fact, I'd prefer something clever with disk labels.

In the best of all possible worlds, the system would recognize the 
bootable partitions, and fail over to the backup one if there was a 
problem with the main one.

I would appreciate some advice here. I need this machine to go live in a 
few days, as the server it's replacing is close to just falling over 
after more than 6 years of active service, all honor to it.

Re: [linux-lvm] Hot backup for boot/root disk

[Toby Bluhm]

Hacksaw wrote:
> I have a Linux system with 2 identical disks for the OS portion. The 
> goal is to have them essentially mirrored, but not continuously. I want 
> to be able to rsync them on occasion.
> 
> I need this disk to be bootable on a moments notice, in case the main 
> one dies.
> 
> The layout of the current boot disk is a partition for /boot which is 
> ext3, and then the rest as a LVM set, of essentially one large partition.
> 
> My first thought is to create the second disk pretty much as the first 
> was created, do the rsyncs, and make some script that will maintain the 
> configuration files which mention the physical disks.
> 
> I have to admit that it's unclear what they all are.
> 
> In fact, I'd prefer something clever with disk labels.
> 
> In the best of all possible worlds, the system would recognize the 
> bootable partitions, and fail over to the backup one if there was a 
> problem with the main one.
> 
> I would appreciate some advice here. I need this machine to go live in a 
> few days, as the server it's replacing is close to just falling over 
> after more than 6 years of active service, all honor to it.
> 

Some people like using LVM for system/OS disks - I don't. So I would
ditch the LVM and use software raid1. I don't understand why you
wouldn't want the disks to be constantly in sync. What if they're out of
sync when a disk dies? However, you could break and rebuild the mirror
at your whim when using sw raid.


--Toby

Re: [linux-lvm] Hot backup for boot/root disk

[Hacksaw]

Toby Bluhm wrote:
>
> Some people like using LVM for system/OS disks - I don't. So I would
> ditch the LVM and use software raid1. I don't understand why you
> wouldn't want the disks to be constantly in sync. What if they're out of
> sync when a disk dies? However, you could break and rebuild the mirror
> at your whim when using sw raid.
>
With the scheme where the main data (user dir's and databases) are on 
the data disks, the OS shouldn't change very often. The more likely 
scenario is that something really dumb has been perpetrated on the OS 
disk, and you'd like to be able to recover from that. With continuous 
syncing, what you have is two volumes messed up in the same way.

With the data volume, I'd actually have mirror or at least RAID it, and 
have snapshots. At least, that the plan.