Jim Callahan wrote: > Is 4096 bytes a large enough page size? > > Apparently the disk drive industry has shifted from 512 byte sectors to > 4096 byte sectors. > http://tilt.lib.tsinghua.edu.cn/docs/tech/tp613_transition_to_4k_sectors.pdf > > Should SQLite maintain a 1:1 ratio between page size and sector size? > or should the page size be a multiple of the sector size? Say 2:1 (8096 or > 8K)? or 4:1 (16K). > > What sizes do other databases use? (SQL Server and Postgres both use 8096 > default)
You mean 8192. > For years, virtual machines (VM) have used 4K pages (I think this started > with IBM VM/370); > while disk drives had 512 byte sectors (an 8:1 ratio). > > With a 2:1 ratio, in terms of seek time, one gets the second page for free. > > Would 8096 bytes (8K) be too much for a multi-tasking embedded device (such > as a smart phone?). You shouldn't even be discussing a hardcoded number. The page size should be equal to the page size of the underlying memory management system. 4K on common x86 systems, 8K on SPARC, etc. Choosing a number smaller than this will cost you in RMW ops whenever the filesystem tries to do an update. Choosing a number larger than this is generally going to waste memory. > > Are there any benchmarks? > > Jim > > > > > > > > On Fri, Mar 4, 2016 at 10:48 AM, Richard Hipp <drh at sqlite.org> wrote: > >> The tip of trunk (3.12.0 alpha) changes the default page size for new >> database file from 1024 to 4096 bytes. >> >> https://www.sqlite.org/draft/releaselog/3_12_0.html >> https://www.sqlite.org/draft/pgszchng2016.html >> >> This seems like a potentially disruptive change, so I want to give >> you, the user community, plenty of time to consider the consequences >> and potentially talk me out of it. >> >> The "Pre-release Snapshot" on the download page >> (https://www.sqlite.org/download.html) contains this change, if you >> want to actually evaluate the latest changes in your application. >> >> We hope to release 3.12.0 in early April, or maybe even sooner, so if >> you want to provide feedback, you should do so without unnecessary >> delay. >> -- >> D. Richard Hipp >> drh at sqlite.org >> _______________________________________________ >> sqlite-users mailing list >> sqlite-users at mailinglists.sqlite.org >> http://mailinglists.sqlite.org/cgi-bin/mailman/listinfo/sqlite-users >> > _______________________________________________ > sqlite-users mailing list > sqlite-users at mailinglists.sqlite.org > http://mailinglists.sqlite.org/cgi-bin/mailman/listinfo/sqlite-users > -- -- Howard Chu CTO, Symas Corp. http://www.symas.com Director, Highland Sun http://highlandsun.com/hyc/ Chief Architect, OpenLDAP http://www.openldap.org/project/
