Working on some facilities/DR/BC planning for our backup FAS8300 cluster. I'm trying to answer the question of "how long a power failure can we withstand without data loss?"
The NVRAM/NVMEM backup battery in each controller has a "lot" of capacity but I'm not trusting what I see for run time.
#Estimating NVMEM battery runtime?
kind niche
Truncated a bit...
DeviceChemistry : LION
ChemistryID : 0x2615
Device Name : bq40z50-R1
ID : 27100076
Manufacturer : Simplo
FW_Version : A0
Manufacturer Date : 11/17/2022
...
Status : Ready
Current : 0 mA
Temperature : 23.45 C
Voltage : 7838 mV
MaxError : 1 %
RemainingCapacity : 1219 mAh
FullChargeCapacity: 1358 mAh
RelativeCharge : 90 %
AbsoluteCharge : 82 %
Bat_Dstg_Cycles : 13
RunTimeToEmpty : 65535 min
AverageTimeToEmpty: 65535 min
AverageTimeToFull : 65535 min
...
expected-load-mwh : 400
SystemPresent : True```65535 is a high suspicious number (16-bit overflow...), and even if true that's >45 days
If expected-load-mwh is "expected load on the battery in milliwatthours
0.4 W / 7.2v = 56mA drain at the mid-point of a 2-cell li-ion battery that's around
1300 mAh / 56 mA = 23.2 hours
which seems reasonable
So, if somebody could check my reasoning here, I'd appreciate it.
Followup question I've already answered: "No. Too bad."
https://kb.netapp.com/on-prem/ontap/Ontap_OS/OS-KBs/Can_ONTAP_be_shutdown_gracefully_by_UPS
open pond
there is no need to shut down ONTAP gracefully. Just let it run until the UPS has no more power. NVRAM takes care that no data is lost.
Battery runtime is also irrelevant since NVRAM content is destaged to flash within the first 60s or so after a power loss, after that the battery is no longer needed
kind niche
there is no need to shut down ONTAP gracefully. Just let it run until the UPS ha...
Is there a document describing the flash de-staging?
(I will look in the KB)
open pond
FAS8300 technical FAQ and FAS8300 SE presentation are two documents in Field Portal that describe that
kind niche
I don't think those are available to customers. I'll look some more later.
I see these nodes use NVDIMMs, and they have two NVMe Flash Cache cards each. I assume it destages to the Flash Cache(s)?
open pond
yep
kind niche
Ok, cool. Thanks - I'll proceed based on this, and dig up the supporting documentation later.
Our backup cluster is in a... suboptimal location and we're debating what to do about it short-term and long-term.
open pond
I'm pretty sure it's okay to share these two slides from the technical presentation in here, nothing really secret about them
