[ale] motherboard RAID versus software RAID

James P. Kinney III jkinney at localnetsolutions.com
Fri Jan 20 15:52:14 EST 2006

On Fri, 2006-01-20 at 16:10 -0500, John Wells wrote:
> Guys,
> I've been running software RAID on one of my servers for some time. It
> works very well.
> I'm now out of space, and am planning to add two additional SATA 250 GB
> drives tonight as an additional RAID 1 array.  I also recently upgraded
> the motherboard to an ASUS A7V-600X. The motherboard has a RAID option for
> SATA drives...as I've never owned any serial ATAs before it's gone unused.
> Would you recommend going with Linux's software RAID for these two drives,
> or should I go with the motherboard's RAID? I have no idea of the quality
> of the MB raid, and I suspect Linux's software RAID might offer more
> flexibility, but wanted to hear opinions from the group.

Hardware RAID has a slight speed advantage. But it has always been
outweighed for me by the flexibility and availability of software RAID.

Here's why:

Hardware RAID. You have a RAID5 3-drive system. Drive B fails. You
replace it and it automatically rebuilds the array. Good.

Software RAID. Same setup. Same problem. When the drive is replaced, it
automatically rebuilds the array. You can control the rebuild speed and
availability of the array data.

Hardware RAID. The controller fails. That model is no longer available.
Buy a new model. It doesn't recognize the existing array since it has
not been initialized. BAD DAY. Must use specialized RAID
extraction/recovery tools to create a virtual drive image for copying
the data to temporarily. Wipe the drives, create new RAID5 stripes, copy
back the image to the drive array. Total time on a 40GB filesystem:
28-24 hours.

Software RAID. No hardware component to fail. Can easily copy the
relevant files and configuration onto a floppy if needed (USB drive more
likely) for backup. Existing hard drives can be cloned and installed
into a secondary box. If the main box has a motherboard issue, pull the
drives, put them in a new box, edit the config files and reinstall
those, reboot, go back to work. Downtime: 1-2 hours (including google
searches for details on how to do this).

BOFH RAID method: Use Software RAID but document it as hardware RAID.
Unplug one drives power cord. Do this during end-of-month financials.
Remind accounting staff of the need to upgrade the backup system and how
they disapproved the funding request last quarter for the upgrade.
Inform the CFO that the recovery process will take about 18 hours since
the tape are stored off-site for Sarbans-Oxally compliance. Pop off to
the pub for 6 hours. Plug back in the power on the "damaged" drive.
telinit to runlevel 1 for the 20 minutes it takes to rebuild the drives.
Bring the system back up to full functionality. Report to the CEO that
even though the requested funding was denied by the CFO, you were able
to "streamline the process" by "multitasking the drive array" and it
would have been faster if that new backup system had been used since it
supports multitasking natively. Accept the sincere thanks from the CEO
for the diligent efforts and go back to the pub to finish the darts game
before the PFY gets too smashed to remember he's buying the next round. 

> Thanks, as always!
> John
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James P. Kinney III          \Changing the mobile computing world/
CEO & Director of Engineering \          one Linux user         /
Local Net Solutions,LLC        \           at a time.          /
770-493-8244                    \.___________________________./

GPG ID: 829C6CA7 James P. Kinney III (M.S. Physics)
<jkinney at localnetsolutions.com>
Fingerprint = 3C9E 6366 54FC A3FE BA4D 0659 6190 ADC3 829C 6CA7
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