Re: Database storage

On Thu, Jul 9, 2009 at 7:29 PM, Greg Stark<gsstark(at)mit(dot)edu> wrote:
> On Fri, Jul 10, 2009 at 1:28 AM, Scott Marlowe<scott(dot)marlowe(at)gmail(dot)com> wrote:
>>
>> $750 is about what a decent RAID controller would cost you, but again
>> it's likely that given your bulk import scenario,  you're probably ok
>> without one.  In this instance, you're probably best off with software
>> RAID than a cheap RAID card which will cost extra and probably be
>> slower than linux software RAID.
>
>
> Fwiw the main disadvantage of software raid is NOT speed -- Linux
> software RAID is very fast. Aside from raid-5 where it lets you
> offload the parity calculation there really isn't much speed benefit
> to hardware raid.
>
> The main advantage of hardware raid is the error handling. When you
> get low level errors or pull a drive a lot of consumer level
> controllers and their drivers don't respond very well and have long
> timeouts or keep retrying tragically unaware that the software raid
> would be able to handle recoverying. A good server-class RAID
> controller should handle those situations without breaking a sweat.

Definitely a big plus of a quality HW controller, and one of the
reasons I don't scrimp on the HW controllers I put in our 24/7
servers. OTOH, if you can afford a bit of downtime to handle
failures, linux software RAID works pretty well, and since quad core
CPUs are now pretty much the standard, it's ok if parity calculation
uses up a bit of one core for lower performing servers like the
reporting server the OP was talking about.