[CentOS] Centos 7 RAID tutorial?

Mon Sep 8 18:58:16 UTC 2014
Dave Stevens <geek at uniserve.com>

Quoting Digimer <lists at alteeve.ca>:

> On 07/09/14 11:01 PM, Keith Keller wrote:
>> On 2014-09-08, Valeri Galtsev <galtsev at kicp.uchicago.edu> wrote:
>>> Even more: system failure or power loss is more likely to destroy all data
>>> on software RAID than on a single drive when there is a lot of IO present
>>> (to the best of my understanding, loss of cache software RAID is using is
>>> more catastrophic compared to journaled filesystem under same
>>> circumstances - somebody may correct me). So, there may be worth thinking
>>> about hardware RAID.
>> I think an essential feature of any md RAID that's not a RAID1 is a UPS
>> and a mechanism for a clean shutdown in case of extended power failure.
>> (An md RAID1 might be okay in this instance, but I wouldn't want to risk
>> it.)  But this is true for any RAID, which is why many controllers come
>> with a BBU (and if you don't have a BBU on your hardware RAID controller,
>> then you absolutely need the UPS setup I described).
>> OTOH, the OP wasn't clear on what he was doing; perhaps he is just
>> playing around, and doesn't care about data preservation at this time.
>> If you're just testing performance then data integrity in the face of a
>> power failure is less of a concern.
>> --keith
> A UPS is certainly better than nothing, but I would not consider it  
> safe enough. A BBU/FBU will protect you if the node loses power,  
> right up to the failure of the PSU(s). I've seen shorted cable  
> harnesses taking out servers with redundant power supplies, popped  
> breakers in PDUs/UPSes, knocked out power cords, etc. So a UPS is  
> not a silver-bullet to safe write-back caching in software arrays.  
> Good, yes, but not perfect.

This is a pretty interesting discussion but has not revealed an  
on-line tutorial. Anyone?


> -- 
> Digimer
> Papers and Projects: https://alteeve.ca/w/
> What if the cure for cancer is trapped in the mind of a person  
> without access to education?
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