Re: Suggestions for a HBA controller (6 x SSDs + madam RAID10)

On Tue, Feb 21, 2017 at 1:40 PM, Wes Vaske (wvaske) <wvaske(at)micron(dot)com>
wrote:

> - HW RAID can give better performance if your drives do not have
> a capacitor backed cache (like the MX300) AND the controller has a battery
> backed cache. **Consumer drives can often get better performance from HW
> RAID**. (otherwise MDADM has been faster in all of my testing)
>

I stopped recommending non-capacitor drives a long time ago for databases.
A capacitor is basically a battery that operates on the drive itself and is
not subject to chemical failure. Also, drives without capacitors tend not
(in my direct experience) to be suitable for database use in any scenario
where write performance matters. There are capacitor equipped drives that
give excellent performance for around .60$/gb. I'm curious what the entry
point is for micron models are capacitor enabled...

MLC solid state drives are essentially raid systems already with very
complex tradeoffs engineered into the controller itself -- hw raid
controllers are redundant systems and their price and added latency to
filesystem calls is not warranted. I guess in theory a SSD specialized
raid controller could cooperate with the drives and do things like manage
wear leveling across multiple devices but AFAIK no such product exists
(note: I haven't looked lately).

merlin