[kwlug-disc] Swapping drives on server

[john at netdirect.ca]

kwlug-disc-bounces at kwlug.org wrote on 01/14/2010 10:49:55 AM:
> From: "Insurance Squared Inc." <gcooke at insurancesquared.com>
> 
> I've got two almost identical servers:
> 1) live server, dell 1750,
> - 1 xeon cpu
> - 1 gig ram
> - no hardware raid, running 1 drive for OS, 2 drives for data on linux 
raid
> This server is live
> 
> 2) backup server, dell 1750
> - 2 xeon cpu's
> - 8 gigs of ram
> - has a hardware raid controller in it that I don't want to make use of
> 
> 
> How boring will my day be if I pull the three drives from server 1 and 
> insert them into server B (I don't mind a few minutes of downtime to 
> make the switch and reboot)?  Did I just upgrade my server?  Or is linux 

> likely to insert some excitement into my life?

I'm guessing that because both are Dell 1750s that both have the same 
chipsets, video, network, etc., etc. Checking 'lspci' on both will tell 
you. If they are the same it will make it easier to move. You will still 
be prompted to reconfigure network controllers.

The big change in moving disks is if you change the controller the disk is 
on or the order of the disks. If the root disk is on a SCSI controller 
then moving to another SCSI controller of the same model (really the same 
driver) is easy. SATA tends to be fine. But from SCSI to RAID card or RAID 
card to a different RAID card requires work that you probably don't want 
to do.

Also the order is important. Many Linuxes still need the disk to be on the 
same ordinal device, so controller 0, disk 0, or that it be on /dev/sda, 
not all of a sudden on /dev/sdb. Things have been changing so that UUIDs 
are used to find disks, but grub may still be confused with a switch.

Here is what I recommend:

Switch them, making sure to keep disks connected to the corresponding 
hardware in the other box.

Alternatively:

You could move the extra RAM and CPU from one box to another.

As long as the system boots then fixing drive mount problems or network 
problems is easy.

NOTE: If you have a live CD that is of similar vintage (just use the same 
distro and version) to the OS installed then fixing boot issues is usually 
simple, but it can often take a couple of boots to get it right.

John Van Ostrand
Net Direct Inc.
 
CTO, co-CEO
564 Weber St. N. Unit 12
map
 
Waterloo, ON N2L 5C6
 
john at netdirect.ca
Ph: 866-883-1172
ext.5102
Linux Solutions / IBM Hardware
Fx: 519-883-8533