[mdlug] New Server - Hardware Configuration

[Aaron Kulkis]

Robert Adkins II wrote:
> It's time to upgrade the old servers here at the office.
>  
> Here's the plan:
>  
> Matched pair of HDs for the Main OS Drive. These will be mirrored.
>  
> Matched Pair or two matched pairs of drives for Filesharing. These will be
> mirrored.
>  
> Separate RAID Card that supports Hot Swap on Linux to allow for two to three
> removable drive bays that will be used to duplicate the entirety of the
> mirrored data drives.
>  
> I have a quote from Dell for a server that uses their Linux Compatible RAID
> cards. Right now, they are quoting three RAID Cards. The onboad card that
> the OS will be booting off of, a second card that will be for the data
> drives and a final card that won't be setup as RAID, which means that it
> won't/shouldn't crap out the kernel while supporting hot swapping.
>  
> Thoughts? Opinions?

Not all Hardware RAID puts the same RAID information on the disks
in an identical fashion -- switching disks from one RAID controller
to a different manufacturer, or even model of RAID card can be,
shall we say, problematic (i.e a *bad* *thing*(tm) in the event
that you have any sort of need to connect the RAID-ed disks to any
controller other  than the original one, especially if 20 minutes
earlier, you had not the slightest intention of doing any such thing).


Do not rely on any hardware RAID that you cannot replace
with identical hardware.

Therefore, you should order extra RAID cards of IDENTICAL make
and model to keep on hand as spares, as there is no guarantee
how long they will be available.

For the same reason, configuring a system for hardware RAID using
an on-motherboard controller is just begging to abused (in the most
embarrassing way possible) by Murphy's law.  Iknow it's not the case
for what you specified, but if you have a system which has only
motherboard RAID, then forego the hardware RAID and use software RAID.
Relying on motherboard RAID in the long term (say, longer than
guaranteed availability of the motherboard within some already
devised contract (3 days? 12 hours? 2 hours?) is also setting
yourself up for failure.

Although slower, software RAID has the advantage that you can
lose a controller card have a no-hitch recovery with ANY card
that you find as a replacement.  Depending on how "mission-critical"
the system is (does downtime annoy one user, or does it bring
the entire company to a halt?) should have an influence on
how you choose to implement your RAID system.


>  
> Thanks.
> 
>