[CentOS] Opteron, Athlon/64, and disaster recovery
Benjamin Smith
lists at benjamindsmith.com
Wed Dec 28 22:21:08 UTC 2005
What it comes down to is this: so far, all the servers I've been administering
have been 32-bit P3/P4/Athlon alikes, so if a server died and we needed it up
NOW we could go to a local computer store here in smalltown USA, buy some
desktop machine, swap harddrives, press enter a few times while kudzu does
its thing, and have a working machine.
Now, we're moving to Opteron-based servers, and I just was wondering if it's
reasonable to expect that, in a worst-case scenario, we could get an
Athlon/64 system locally, and have it work, even if not optimally.
Obviously, the Opteron is better and faster, but if the Athlon 64 will run
CentOS X86/64, then I can be pretty certain that in the worst case, I can run
to the local Performance Leet g4m3rz store, and get an Athlon/64 to get a
needed database server back online.
Just checking the accuracy of the data behind my decisions. (I've turned down
Xeon servers for this reason)
-Ben
On Wednesday 28 December 2005 12:57, Bryan J. Smith wrote:
> Benjamin Smith <lists at benjamindsmith.com> wrote:
> > Has anybody here taken a HDD configured with an Opteron
> > system, and then put it into an Athlon/64 and had it work?
> > Are they interchangeable, like an Athlon/32 and a P3/P4?
>
> Yes, to a point.
> An x86 system will _not_ boot a x86-64 kernel.
> But yes, a x86-64 system _will_ boot a x86 kernel.
>
> The x86-64 kernel puts the CPU into a 52-bit PAE memory mode.
> x86 systems only support a 36-bit PAE memory mode.
> For more, see my blog entry here:
>
>
http://thebs413.blogspot.com/2005/10/what-is-x86-64-long-mode-memory-model.html
>
>
> The only other issues are boot-time storage support. Most
> [parallel] ATA devices are no issue, because they are in the
> stock ATA/IDE kernel support. SATA is a different issue,
> because many SATA drivers are SCSI block drivers at this
> point, so they need to be built into the initrd (initial root
> disk).
>
> Linux isn't like NT 5.x (2000/XP/2003), which sets boot-time
> information in the registry and will blue screen if you
> change mainboard/chipsets. Yes, not even changing the
> ntbootdd.sys file for the appropriate ATA/SCSI works (like it
> did for NT 4.0 and earlier). The only way to change that is
> to boot up another OS (e.g., Linux) with a registry editor
> and manually change the 3 or so keys for the boot-time
> storage device.
>
> --
> Bryan J. Smith Professional, Technical Annoyance
b.j.smith at ieee.org http://thebs413.blogspot.com
> ----------------------------------------------------
> *** Speed doesn't kill, difference in speed does ***
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