Before the upgrade, the fan noise was generally minimal with fan speeds between 1K-1.5K rpm and drives kept at a uniform temperature of 48-53 degrees C regardless of load or whether idle which is about perfect for seagate enterprise nas disks.
After the upgrade, quiet mode is letting disk temperatures - even when relatively idle reach 50-56 degrees with wide variation between disks. This is the default quiet mode. I worry that we might have short spikes to 58-60 degrees when the disks come under intense load.
Unfortunately, switching to balanced mode results in fan speeds increasing to 3K+ rpm and very high noise...I didn't bother to try 'cool' mode.
Opening a support case is unnecessary. Your logs show you were only in Balanced mode for 3 minutes, which really didn't give the system a chance to cool down into the new temperature range.
Stay in Balanced mode if you want your disks to run at a lower temperature. The fan won't stay at 3K RPM forever unless it really needs to. It will only stay in that range long enough to get the disk temps down to the new lower threshold.
OK, so on the first try, I aborted the balance fan mode test due to complaints from those in the same room as the NAS that it was making it impossible to work when FAN was at 3600RPM.
This time, I provided warning that the loud noise would go away after 5 minutes....and it did, but things still aren't right.
Before 6.5 firmware, Drives averaged around 50-52 degrees and never went over 54. Fan noise was never problem.
Quiet mode is now having them average 52-54 and the highest temperature we see is spikes at 56 degrees. This is a tad too high for our liking. Average Fan RPM seemed to be between 800-1400rpm, with 1200 the most frequent. Quiet mode is however indeed quiet.
On to the new balanced, the fan has stabilized at 1802rpm - a huge bump up and really more than what was needed. Drives are now averaging ~45 degrees. We only wanted to reduce drive temps back to pre 6.5 status...2-4 degrees, not the 6-9 degrees and +600rpm. The increased fan speed is not horribly loud, but it is much louder than we'd like and I'm not sure how much power it is using. I'm guessing if we could manually set to ~1400-1500, about half way between quiet and balanced - we'd get closer to pre 6.5 behavior.
In general temperatures for disks under 60 degrees are fine.
Well, that depends on what you mean by "fine". The temps are within the manufacturer specs (which might be "fine" for many people), But I don't think they are optimal.
One study has found that drive failure rate starts to climb as drive temps go above 34 degrees C (http://www.cs.virginia.edu/~gurumurthi/papers/acmtos13.pdf figure 5) Table 2 in the same study shows that drives running at 55C have an AFR (annualized failure rate) that is twice that of drives running at 40C.
Google's classic drive study found a weaker correlation between drive temp and failure rate. Though they weren't focused exclusively on temperature, they did find higher failure rates with drive temps above 45 C.
BackBlaze sees no general correlation - although they did find a correlation for some drive models. But their drives are all run between 20-30 degrees C.
I'm guessing if we could manually set to ~1400-1500, about half way between quiet and balanced - we'd get closer to pre 6.5 behavior.
There are multiple ways to do that. The simplest way is to go back to Quiet mode and write, say, 1400 to /etc/frontview/min_fan_speed_override. This should work, after rebooting:
