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?
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