[CentOS] RAID 6 - opinions

Fri Apr 12 00:25:02 UTC 2013
John R Pierce <pierce at hogranch.com>

On 4/11/2013 5:04 PM, David C. Miller wrote:
> The LSI 9200's I use are nothing more than a dumb $300 host bus adapter. No RAID levels or special features. I prefer to NOT use hardware RAID controllers when I can. With a generic HBA the hard drives are seen raw to the OS. You can use smartctl to poll and test the drives just like they were connected to a generic SATA bus on the motherboard. The tools built into Linux(smartd & md) are better suited and more flexible at reporting problems and handling every level of RAID. It also makes migrating the array to another system trivial. I don't have to worry about finding the exact same RAID controller. Just a no frills SAS/SATA HBA will do.

yeah, until a disk fails on a 40 disk array and the chassis LEDs on the 
backplane don't light up to indicate which disk it is and your 
operations monkey pulls the wrong one and crash the whole raid.

have fun with that!

if you can figure out how to get the drive backplane status LEDs to work 
on Linux with a 'dumb' controller plugged into a drive backplane, PLEASE 
WRITE IT UP ON A WIKI SOMEWHERE!!!   everything I've seen leaves this 
gnarly task as an exercise to the reader. With a card like a 9261-8i, it 
just works automatically.

also, hardware raid controllers WITH battery backed (or flash backed) 
cache can greatly speed up small block write operations like directory 
entry creates, database writes, etc.

john r pierce                                      37N 122W
somewhere on the middle of the left coast