Willing to bet that there was slicing on both sides of that conversation
and this is what I will now refer to as the expected and resulting razor
burn.
Babak Pasdar wrote:
Thanks James,
At signup we asked for N+1 power, two circuits to different UPS units.
I think they sliced it thin by connecting us to two battery packs on
the same UPS. When the UPS controller crashed both battery packs went
down. Which now raises the question -- is it reasonable to have to
specify and expect that two UPS units means that they do not share any
common points of failure.
Is the UPS the battery or the battery and controller combined?
Babak
On 10/23/23 15:16, James Jun wrote:
On Mon, Oct 23, 2023 at 10:38:09AM -0400, Babak Pasdar wrote:
I wanted to get some feedback as to what is considered standard A/B
power setup when data centers sell redundant power.?? It has always
been
my understanding that A/B power means individually unique and
preferably
alternate path connections to disparate UPS units.
Generally speaking, the definition of A/B has become muddied in
recent decades. It has almost become an inaccurate marketing term.
Most sane people have the opinion (myself included) that when "A/B"
power is offered, it is at minimum offererd as 2N UPS (different
building entrance and MSBs and even physically separate UPS rooms are
also desired on a true 2N A/B, but may not always be available).
Some data center operators go even further and architect load
switching within their distribution, thereby preventing
single-side/one-leg power outages for customers during most of their
power maintenance activities
Some data center operators treat "A/B" as convenience for them to
undertake maintenance and offload uptime responsibilities to their
own customers, and require them to either undertake their own
transfer switching and/or dual-cord every equipment, so that they can
keep taking one side of the power system down for repeated
maintenance. This does not scale well for retail colo, as not every
customer is going to be good at maintaining two PSUs for every single
piece of equipment.
Some data centers also view "N+1" system deployment at the UPS as an
acceptable form of A/B protection, as long as customer circuits are
on different PDUs.
Long story short, whether you're receiving N+1 or 2N or 1N, it's
important to inquire about how your power circuits will be
architected and delivered by the data center, and either have that
codified in the contract or reflected appropriately in SLA offering.
There is nothing wrong with the data center providing N+1 or 1N
power, as long as they're transparent about it and that it is what
you're willing to accept for the right terms. However, simply
accepting "we are providing you A/B power" or "we've never had
primary power failure" are not sufficient to meet proper due
diligence during a site selection process, unless you can accept the
site outage occurring from time to time, or you're deploying your own
power plant (i.e. DC power and batteries) to supplant data center's
own power protection scheme.
James
