On Wed, Dec 13, 2017 at 4:30 PM, Andres Freund <and...@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
