Re: SQLite and ext3 journalling mode

On 12/08/2010 06:52 AM, Dan Kennedy wrote:
> On 12/07/2010 04:31 AM, Ted Ts'o wrote:
>> On Tue, Dec 07, 2010 at 01:42:08AM +0700, Dan Kennedy wrote:
>>>
>>> Are SQLite users that are worried about losing data that has been
>>> committed (fsynced) better off setting data=journal than
>>> data=ordered (or even data=writeback)?
>>
>> Well, they won't be better off a data integrity point of view.
>> Depending on how SQLite is configured, and how many fsync's are issued
>> by SQLite in response to application queries, and depending on your
>> background workload by other applications, using data=journal *might*
>> be a performance win.
>>
>> In general, though, if you have background workloads that are
>> downloading torrents, data=journal is going to hurt a lot.  So I don't
>> recommend it except for fairly specialized deployments where there's
>> only one primary user of the file system.
>
> Thanks. But to be clear, is data=ordered better than data=writeback
> wrt. data integrity following a power failure?
>
> Regards,
> Dan.
>

Data integrity can mean a couple of different things.

If you are file system meta-data centric (i.e., a file system developer or just 
worried about having to run fsck after a crash to repair the file system), then 
both options *should* be equivalent.

If you are one of those annoying users who define data integrity to include 
those annoying details like will my file have garbage in it after a crash that 
will make my DB or other app puke, then data ordered is clearly more robust.

Note that most distributions (including RHEL) support & focus testing only 
ordered mode....

Hope this helps :)

Ric