Speed tests on cached filesystems don't do what is expected. The kernel will write into RAM as much as it can, and leave the actual I/O for later.
On Thu, Jun 23, 2022 at 12:39 PM Jakub Juszczakiewicz via Dng < [email protected]> wrote: > Hi list, > > What is time between call dd? On ext filesystems is implemented > delay before physically write date on disk. It's for e.g. minimally > files fragmentation. Second question is that, did you try call "sync" > command after each of writes? > > --- > Best regards, > Jakub Juszczakiewicz > Krypto-IT > > W dniu 2022-06-23 14:27, Radisson via Dng napisał(a): > > Its a normal HD i guess 4096 is ok, > > but i do not think that this matters. > > > > > > Am 23.06.22 um 13:11 schrieb Rich W: > >> Hi, > >> > >> A blocksize of 1G seems extreme. > >> What is the optimal blocksize of the output device? > >> > >> Cheers, > >> -Rich > >> > >> > >> On Thu, Jun 23, 2022, 4:52 AM Radisson via Dng <[email protected]> > >> wrote: > >> > >>> Hi list, > >>> i found a strange ext4 (?) effect. > >>> > >>> when i write to a disk: > >>> dd if=/dev/zero of=xx bs=1G count=1 > >>> > >>> reports 2.6 GB (expected) > >>> doing again speed drops to 200MB. > >>> > >>> removing xx restores old speed. > >>> > >>> I ask the net and it seems that the effect is there > >>> since kernel 2.6. I found the explainations a bit confusing. > >>> > >>> does anyone know more ? > >>> > >>> note: i was analysing a performace issue for mysql and i am > >>> not sure if that problems matters outside tests. > >>> > >>> re > >>> rp > >>> > >>> _______________________________________________ > >>> Dng mailing list > >>> [email protected] > >>> https://mailinglists.dyne.org/cgi-bin/mailman/listinfo/dng > >>> > >> > > _______________________________________________ > > Dng mailing list > > [email protected] > > https://mailinglists.dyne.org/cgi-bin/mailman/listinfo/dng > _______________________________________________ > Dng mailing list > [email protected] > https://mailinglists.dyne.org/cgi-bin/mailman/listinfo/dng > -- Bruce Perens K6BP
_______________________________________________ Dng mailing list [email protected] https://mailinglists.dyne.org/cgi-bin/mailman/listinfo/dng
