Quote Originally Posted by Mastakilla View Post
Quote Originally Posted by Tiltevros View Post
www.span.com
there 2 ways that the power losses.. 1 way i dont know how to say it in english... but i will try to express it in my own way... the power goes up and then dives down like eg if ur power socket ensure in stady way 220volts for miliseconds goes to 260volts then to 175Volts and then 220volts that power goes in to ur psu and after psu inside ur pc. the second way is when the power goes from 220 stady volts to 175volts and then goes up to the 260 volts. the second way for me is more more more dangerous couse the loss of the power reduse from minimum to max and that gap is very painfull to electronics.
ALL serius RAID controllers have bbu's. when u work ur data for seconds are on the cache of the controller those 512mb or more that the controller have. if the power loss hit u in that moment ur data stays in the controllers cache for 72 hours top. thats what u pay for the bbu. For a home user maybe this bbu is useless but for enteprises is gold.
Now for home users the only benefit that the bbu stands is for Write Cache Back. if u dont have the bbu u cant enable it.
was that a one time offer at span.com when you got the controller and battery for only 412 euro?
Cause now I see the LSI 9260-8I for 421,42 euro and the battery for 120,90...

I have 2 APC SurgeArrests for 8 outlets each to protect all my electronic devices, so power spikes shouldnt be a problem.
Power drops and complete power loss however can still occur.

In case of power loss I wouldnt mind very much to loose what i was working on. However the chance of loosing all data because of power loss causing a corrupt RAID 5 is unacceptable (that is the reason why I'm investing in this expensive RAID controller, I do not want the chance anymore to loose all data. And I'm tired of putting everything on DVDs :p)

So can anyone confirm that I don't need a BBU to ensure that I will not loose all data?

About the write back cache: Interesting... I didnt know you cant enable it without a BBU... Does it matter much in performance? Or where lies the difference?

Thanks!
It seems Tiltevros statement about "not being able to enable write back without a BBU" was incorrect.

I just enabled write back cache without having a BBU and got almost 1000% write speed increase...

But my old question about the BBU still wasn't answered...

So I'll ask it again:
Is it possible to loose the complete RAID 5 IF
* write back is enabled
* there is no BBU
* a powerloss occurs or a system / application crash occurs

OR will this only cause me to loose the data in the cache (+ a bit of corresponding data that was already on the disc)?