Re: test_fsync label adjustments

On Jan 18, 2011, at 5:41 PM, Bruce Momjian wrote:

> A.M. wrote:
>>>> Because the fastest option may not be syncing to disk. For example,
>>>> the only option that makes sense on OS X is fsync_writethrough- it
>>>> would be helpful if the tool pointed that out (on OS X only, obviously).
>>>
>>> Yes, that would be a serious problem.  :-(
>>>
>>> I am not sure how we would address this --- your point is a good one.
>>
>> One general idea I had would be to offer some heuristics such as "this
>> sync rate is comparable to that of one SATA drive" or "comparable to
>> RAID 10 with X drives" or "this rate is likely too fast to be actually
>> be syncing". But then you are stuck with making sure that the heuristics
>> are kept up-to-date, which would be annoying.
>
> That fails for RAID BBUs.

Well, it's nothing more than a heuristic- it is still nice to know whether or not the fancy hardware RAID I just setup
issimilar to Josh Berkus' RAID setup or a single SATA drive (which would hint at a misconfiguration). As you said,
perhapsa wiki is better for this. But a wiki won't integrate with this tool, which I why I would hesitate to point
novicesto this tool... should the tool point to the wiki? 

>
>> Otherwise, the only option I see is to detect the kernel and compare
>> against a list of known problematic methods. Perhaps it would be easier
>> to compare against a whitelist. Also, the tool would likely need to
>> parse "mount" output to account for problems with specific filesystems.
>>
>> I am just throwing around some ideas...
>
> That sounds pretty complicated.  One idea would be the creation of a
> wiki where people could post their results, or ideally a tool that could
> read the output and load it into a database for analysis with other
> results.

The OS X example is pretty cut-and-dry- it would be nice if there were some kind of hints in the tool pointing in the
rightdirection, or at least a few words of warning: "the fastest option may not be the safest- read the docs". 

Cheers,
M