In the past couple of months there have been several customers asking me many questions around their current practices of OS disk mirroring with respect to Solaris 10 volume management. These questions are due to the differences between the SPARC boot architecture ( Openboot ) and the x86/x64 boot architecture (BIOS & GRUB).
What I have come to learn from these questions are: mirroring of the OS disks is being used to solve problems (Failsafe Boot and Alternate Boot Environments) in which mirroring was not intended to solve; the process to make mirroring solve these other problems can leave one without disk protection, be complex, and be difficult to setup; and, these problems were solved along time ago by using Live Upgrade.
Disk mirroring does a good job of protecting against disk failures. And it is a good practice to mirror your OS Disks. So let's leave it in place and use Live Upgrade with mirrored OS disks to create a failsafe and alternate environment that can be independently patched, upgraded, flashed, and booted.
Suggestions:
In a 2 OS disk configuration:
Okay just in case you don't have the ability to do h/w raid via built-in controller. Here's how you would mirror the root disks with Solaris Volume Manager - here's how on SPARC. And for x86 here's how.
Note: you need to reserve some slice(s) for Live Upgrade. And they should be mirrored if you are going to switch back and forth between the two environments in production.
Ah! Now I can sleep better.
What I have come to learn from these questions are: mirroring of the OS disks is being used to solve problems (Failsafe Boot and Alternate Boot Environments) in which mirroring was not intended to solve; the process to make mirroring solve these other problems can leave one without disk protection, be complex, and be difficult to setup; and, these problems were solved along time ago by using Live Upgrade.
Disk mirroring does a good job of protecting against disk failures. And it is a good practice to mirror your OS Disks. So let's leave it in place and use Live Upgrade with mirrored OS disks to create a failsafe and alternate environment that can be independently patched, upgraded, flashed, and booted.
Suggestions:
In a 2 OS disk configuration:
- H/W raid the 2 OS disks - On a T2000 here's how. On a x4200 here's how.
- Partition your h/w mirrored disk with Live Upgrade in mind - OS requires about 5GB so Live Upgrade space needs same.
- - Here's my general suggestions for x86:
- FDISK into at least 2 Primary Partitions - 3 if you want.
- Use first Partition for Production
- Use 2nd Partition for Live Upgrade (Failsafe/Alternate Boot Environment).
- - Here's my thoughts for SPARC:
In a 4 OS disk configuration:
- Since you will only have 1 device (h/w mirrored) and 7 slices you need to plan out your filesystem layout carefully.
- If at all possible keep the same number of slices for the original boot environment the same as the Live Upgrade (Alternate boot environment). A 4 disk configuration with 2 - 2 disk mirrors will help if you run into slice constraints. Or you can have your Live Upgrade environment use fewer slices. The downside of doing that is you won't keep your alternate boot environment with the same disk layout; thus, making it necessary to patch and test your alternate boot environment once okay then patch the original environment causing more downtime with respect to reboots.
- Do the same as a 2 disk config but with 2 h/w raid mirror sets (2 - 2 disk mirrors). The first mirror set would be my production and the second mirror set would be for Live Upgrade.
Okay just in case you don't have the ability to do h/w raid via built-in controller. Here's how you would mirror the root disks with Solaris Volume Manager - here's how on SPARC. And for x86 here's how.
Note: you need to reserve some slice(s) for Live Upgrade. And they should be mirrored if you are going to switch back and forth between the two environments in production.
Ah! Now I can sleep better.
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