Re: Enabling Checksums

On Mon, Mar 18, 2013 at 1:31 PM, Greg Smith <greg@2ndquadrant.com> wrote:
> On 3/18/13 10:52 AM, Bruce Momjian wrote:
>>
>> With a potential 10-20% overhead, I am unclear who would enable this at
>> initdb time.
>
>
> If you survey people who are running PostgreSQL on "cloud" hardware, be it
> Amazon's EC2 or similar options from other vendors, you will find a high
> percentage of them would pay quite a bit of performance to make their
> storage more reliable.  To pick one common measurement for popularity, a
> Google search on "ebs corruption" returns 17 million hits.  To quote one of
> those, Baron Schwartz of Percona talking about MySQL on EC2:>
> "BTW, I have seen data corruption on EBS volumes. It’s not clear whether it
> was InnoDB’s fault (extremely unlikely IMO), the operating system’s fault,
> EBS’s fault, or something else."

Clarification, because I think this assessment as delivered feeds some
unnecessary FUD about EBS:

EBS is quite reliable.  Presuming that all noticed corruptions are
strictly EBS's problem (that's quite a stretch), I'd say the defect
rate falls somewhere in the range of volume-centuries.

I want to point this out because I think EBS gets an outsized amount
of public flogging, and not all of it is deserved.

My assessment of the caustion at hand: I care about this feature not
because EBS sucks more than anything else by a large degree, but
because there's an ever mounting number of EBS volumes whose defects
are under the responsibility of comparatively few individuals.

--
fdr