It would be useful to know more details -- how much storage space you
need for example.
fwiw I considered all of these issues when we first deployed SSDs and
decided to not use RAID controllers.
There have not been any reasons to re-think that decision since.
However, it depends on your specific
needs I think. We prefer to think in terms of a single machine as the
unit of service failure -- a machine
is either working, or not working, and we ensure state is replicated to
several machines for durability.
Therefore a storage solution on each machine that is more reliable than
the machine itself is not useful.
In our deployments we can't max out even one SSD, so there isn't
anything a RAID controller can
add in terms of performance, but your case could be different.
You might also want to consider the power dissipated by the RAID
controller : I was quite surprised by how much heat they generate, but
this was a couple of years ago. Possibly there are lower power
controllers available now.
You need the capacitor on the SSD -- a RAID controller with BBU will not
fix a non-power-fail-safe SSD.
On 4/4/2014 10:04 AM, Steve Crawford wrote:
>
> I've been looking into upgrading to SSD and wondering about RAID and
> where to apply $$$ as well. In particular I'm curious about any
> real-world PostgreSQL-oriented performance and data-protections advice
> in the following areas:
>
> 1. With SSDs being orders of magnitude faster than spinning media,
> when does the RAID controller rather than the storage become the
> bottleneck?
>
> 2. Do I need both BBU on the RAID *and* capacitor on the SSD or just
> on one? Which one? I'm suspecting capacitor on the SSD and
> write-through on the RAID.
>
> 2. Current thoughts on hardware vs. software RAID - especially since
> many of the current SSD solutions plug straight into the bus.
>
> 3. Potential issues or conflicts with SSD-specific requirements like TRIM.
>
> 4. Manufacturers, models or technologies to seek out or avoid.
>
> 5. At what point do we consider the RAID controller an additional SPOF
> that decreases instead of increases reliability?
>
> 6. Thoughts on "best bang for the buck?" For example, am I better off
> dropping the RAID cards and additional drives and instead adding
> another standby server?
