Exploring some back-up / redundancy options thoughts?

[rongoodman]

Can you expand on that?

If you have two computers running different algorithms, they will disagree on what they're telling you to do, so which one will you follow? One won't be backing up the other in case of a failure, because they're running two different programs in the first place. The solution is to either buy computers that can run standard software, such as VPM or Buhlmann GF, or buy two of the same or similar computers if they're running a proprietary program, such as Suunto RGBM.

 

[FredGarvin]

Get the Aeris OLED AI computer and a small SPG on the other HP port clipped to the left waist D ring DIR style.

And no redundant computer back-up?

Garvelous

---------- Post added June 19th, 2014 at 09:46 AM ----------

If you have two computers running different algorithms, they will disagree on what they're telling you to do, so which one will you follow? One won't be backing up the other in case of a failure, because they're running two different programs in the first place. The solution is to either buy computers that can run standard software, such as VPM or Buhlmann GF, or buy two of the same or similar computers if they're running a proprietary program, such as Suunto RGBM.

Spot on answer!

I understand that all Aeris/Oceanic/Hollis and Sherwood use the same algorithm.



Garv

 

[Tortuga68]

If you have two computers running different algorithms, they will disagree on what they're telling you to do, so which one will you follow?

The more conservative one or the one that is still working

---------- Post added June 20th, 2014 at 01:51 AM ----------

And no redundant computer back-up?

Are you doing decompression dives?

 

[FredGarvin]

I would suggest you consider the following questions: How likely is a failure? What is the worst outcome if I have a failure?



I had a primary A.I. computer failure the first time I used my Sherwood Wisdom. That experience left a bad taste. I am not tech diving, nor cave, trimix nor wreck penetration, but I still dive deep on air (100-130) and tend to wander, so as one with some life experience, a physician by training and flown planes as a student pilot I tend to prefer a modicum of redundancy, especially if my life and/or my enjoyment of a hobby is dependent on it.

If I travel to dive, I want to be able to dive and not abort. Aborting a dive is not a cost effective way to enjoy a dive vacation IMHO.


Garvelous

 

[Tortuga68]

Fair enough.

Have you considered getting a third computer in case the first two fail?

---------- Post added June 20th, 2014 at 02:01 AM ----------

I'll answer for you... No, you haven't. Why? Because the chances of 3 failures in a row are so low that it's ridiculous; and the consequences are not severe

Planes have triple redundancy because you fall out of the sky and die

 

[FredGarvin]

If you choose 2 different computers ensure they are using the same algorithm otherwise there is little point. Also, personally if you don't trust AI enough that you need back up you've lost one of the benefits of AI. I default to a simple spg and awareness of consumption/depth/time.


Sent from my iPhone using Tapatalk

I want to make sure I am clear on your thoughts. I am concerned with 2 variables, the loss of a computer due to catastrophic failure of the unit, the loss of the wireless connection too.

In the event of a signal loss or catastrophic computer failure, the presence of an analog SPG as back-up to an A.I. wrist mount will tell me my remaining air pressure but will do nothing for my dive planning, no dc time etc..

Garv

---------- Post added June 19th, 2014 at 10:14 AM ----------

Fair enough.

Have you considered getting a third computer in case the first two fail?

---------- Post added June 20th, 2014 at 02:01 AM ----------

I'll answer for you... No, you haven't. Why? Because the chances of 3 failures in a row are so low that it's ridiculous; and the consequences are not severe

Planes have triple redundancy because you fall out of the sky and die

Tortuga,

While I appreciate your thoughts, I have never suggested triple redundancy in any of my posts on this subject.

I am trying to remain rational and reasonable, not ridiculous.

If one were interested and could afford it, one could carry ten computers but as you suggest the risk of one failure is low enough that this much redundancy would be regarded as wasteful and "ridiculous".

But in no way do I believe having one extra computer is too much, perhaps "ridiculous."

Back when I learned to dive - stone age with dinosaurs sharing the water with me - having a safe second was considered too much and "ridiculous". It was deemed that only DiveMasters and Instructors should have such new fangled devices.

Finally, your statement, "Planes have triple redundancy because you fall out of the sky and die", is factually incorrect.

Small planes, like those I flew, have limited redundancy, nothing like the commercial airliners to which I assume you refer.

Lastly planes do not simply fall out of the sky when there is a failure, they can glide quite a distance.

see: Air Transit Flight 236
Air Transat Flight 236 - Wikipedia, the free encyclopedia

Garvelous

 

[Gren]

If I follow your suggestion I would have:

1. An analog SPG hanging off my back connected to the First Stage
2. Two wrist mounted computers , one that is wireless A.I. the other simply a stand-alone wrist mount.

(3 items total : 1 hose + 2 wrist units)

versus:

1. One hose connected. A.I. console
2. One wireless wrist mount, A.I. computer

(Two items total : 1 hose + 1 wrist unit)

Seems like option #2 is more streamlined and simple.

The Sherwood Wisdom Console is not that much bigger than my analog Highland SPG.

I could dump the SPG and Sherwood Wisdom console and use the Aeris OLED 300 Wrist A.I. and a back up wrist A.I.

Garvelous

OK I missed that the console was AI. I was thinking a 3 gauge console. Personally, I would want a spg as my backup. As far as wrist computers go, I wear a Predator and a Hollis DG03 on the same arm and they don't get in the way.


Sent from my Nexus 7 using Tapatalk

 

[Hatul]

Excellent advice regarding disparate algorithms, you are correct the Sunnto line uses a different one than Aeris/Oceanic/Hollis line.

I did ponder that too, but thought using a more conservative unit such as the Sunnto may be beneficial in the event of a primary computer failure.

As for, "My vote is go with the wrist mounts and use a small spg instead of the console. This give you the benefit of being more streamlined and as mentioned above, you can loan one out to a buddy if they have a failure."

If I follow your suggestion I would have:

1. An analog SPG hanging off my back connected to the First Stage
2. Two wrist mounted computers , one that is wireless A.I. the other simply a stand-alone wrist mount.

(3 items total : 1 hose + 2 wrist units)

versus:

1. One hose connected. A.I. console
2. One wireless wrist mount, A.I. computer

(Two items total : 1 hose + 1 wrist unit)

Seems like option #2 is more streamlined and simple.

The Sherwood Wisdom Console is not that much bigger than my analog Highland SPG.

I could dump the SPG and Sherwood Wisdom console and use the Aeris OLED 300 Wrist A.I. and a back up wrist A.I.

If things went to Sht, I would simply abort the dive and not know my remaining air pressure.

I have experienced a total Sherwood Wisdom failure and like redundancy as a result.

Garvelous

In that case a good option is to keep your Sherwood Wisdom 2 as a complete SPG/computer backup, and get the Aeris OLED AI computer as the primary. Only requires one purchase and backs up everything. I think the Sherwood follows the DSAT algorithm which is liberal, so you should be fine using it as a backup.

 

[kr2y5]

Planes have triple redundancy because you fall out of the sky and die.

AFAIK, this is also to support a voting logic, which requires 2*N+1 replicas to tolerate N failures, so that the remaining working ones can form the N+1 majority vote.

 

[Jim Lapenta]

Get an SPG, sell all the computers you have now. Buy a pair of Shearwater Petrels and you will never have to buy another computer for the rest of your life.