On 01/10/2014 11:59 PM, Joshua D. Drake wrote:
>
> On 01/10/2014 02:57 PM, Stephen Frost wrote:
>
>> Yes, if you have a BBU that memory is authoritative in most
>> cases. But
>> in that case the argument of having two disks is pretty much
>> pointless,
>> the SPOF suddenly became the battery + ram.
>>
>>
>> If that is a concern then use multiple controllers. Certainly not
>> unheard of- look at SANs...
>>
>
> And in PostgreSQL we obviously have the option of having a third or
> fourth standby but that isn't the problem we are trying to solve.
The problem you are trying to solve is a controller with enough
Battery Backed Cache RAM to cache the entire database but with
write-though mode.
And you want it to degrade to write-back in case of disk failure so that
you can continue while the disk is broken.
People here are telling you that it would not be safe, use at least RAID-1
if you want availability
Cheers
--
Hannu Krosing
PostgreSQL Consultant
Performance, Scalability and High Availability
2ndQuadrant Nordic OÜ