On Wed, Dec 13, 2017 at 4:30 PM, Andres Freund <andres@anarazel.de> wrote:
> On 2017-12-13 16:02:45 +0900, Masahiko Sawada wrote:
>> When we add extra blocks on a relation do we access to the disk? I
>> guess we just call lseek and write and don't access to the disk. If so
>> the performance degradation regression might not be much.
>
> Usually changes in the file size require the filesystem to perform
> metadata operations, which in turn requires journaling on most
> FSs. Which'll often result in synchronous disk writes.
>
Thank you. I understood the reason why this measurement should use two
different filesystems.
Regards,
--
Masahiko Sawada
NIPPON TELEGRAPH AND TELEPHONE CORPORATION
NTT Open Source Software Center
