Re: [DNG] strange effect on overwrite
ael via Dng wrote: > Isn't conv=sync needed to make sure that you are not just seeing buffer > effects? Better oflags=sync,direct rather than conv=sync though both are similar in result. Bob signature.asc Description: PGP signature ___ Dng mailing list Dng@lists.dyne.org https://mailinglists.dyne.org/cgi-bin/mailman/listinfo/dng
Re: [DNG] strange effect on overwrite
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 < dng@lists.dyne.org> 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 > >> 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 > >>> Dng@lists.dyne.org > >>> https://mailinglists.dyne.org/cgi-bin/mailman/listinfo/dng > >>> > >> > > ___ > > Dng mailing list > > Dng@lists.dyne.org > > https://mailinglists.dyne.org/cgi-bin/mailman/listinfo/dng > ___ > Dng mailing list > Dng@lists.dyne.org > https://mailinglists.dyne.org/cgi-bin/mailman/listinfo/dng > -- Bruce Perens K6BP ___ Dng mailing list Dng@lists.dyne.org https://mailinglists.dyne.org/cgi-bin/mailman/listinfo/dng
Re: [DNG] strange effect on overwrite
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 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 Dng@lists.dyne.org https://mailinglists.dyne.org/cgi-bin/mailman/listinfo/dng ___ Dng mailing list Dng@lists.dyne.org https://mailinglists.dyne.org/cgi-bin/mailman/listinfo/dng ___ Dng mailing list Dng@lists.dyne.org https://mailinglists.dyne.org/cgi-bin/mailman/listinfo/dng
Re: [DNG] strange effect on overwrite
On Thursday 23 June 2022 at 15:41:21, Dr. Nikolaus Klepp via Dng wrote: > This does not make sense to me: > > >> dd if=/dev/zero of=xx bs=1G count=1 > > >> > > >> reports 2.6 GB (expected) > > IMO ~ 1GB is expected, not 2.6: > > $ dd if=/dev/zero of=xx bs=1G count=1 > 1+0 Datensätze ein > 1+0 Datensätze aus > 1073741824 Bytes (1,1 GB, 1,0 GiB) kopiert, 0,617959 s, 1,7 GB/s I agree with what you say, but I had the impression that Radisson was trying to say that the transfer rate was 2.6 Gbps the first time, and 200 Mbps the second time. Antony. > Anno domini 2022 Thu, 23 Jun 14:27:59 +0200 Radisson via Dng scripsit: > > 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 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 -- .evah I serutangis sseltniop tsom eht fo eno eb tsum sihT Please reply to the list; please *don't* CC me. ___ Dng mailing list Dng@lists.dyne.org https://mailinglists.dyne.org/cgi-bin/mailman/listinfo/dng
Re: [DNG] strange effect on overwrite
On Thu, Jun 23, 2022 at 03:41:21PM +0200, Dr. Nikolaus Klepp via Dng wrote: > > >> > > >> 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. Isn't conv=sync needed to make sure that you are not just seeing buffer effects? ael ___ Dng mailing list Dng@lists.dyne.org https://mailinglists.dyne.org/cgi-bin/mailman/listinfo/dng
Re: [DNG] strange effect on overwrite
This does not make sense to me: > >> dd if=/dev/zero of=xx bs=1G count=1 > >> > >> reports 2.6 GB (expected) IMO ~ 1GB is expected, not 2.6: $ dd if=/dev/zero of=xx bs=1G count=1 1+0 Datensätze ein 1+0 Datensätze aus 1073741824 Bytes (1,1 GB, 1,0 GiB) kopiert, 0,617959 s, 1,7 GB/s Nik Anno domini 2022 Thu, 23 Jun 14:27:59 +0200 Radisson via Dng scripsit: > 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 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 > >> Dng@lists.dyne.org > >> https://mailinglists.dyne.org/cgi-bin/mailman/listinfo/dng > >> > > > ___ > Dng mailing list > Dng@lists.dyne.org > https://mailinglists.dyne.org/cgi-bin/mailman/listinfo/dng > -- Please do not email me anything that you are not comfortable also sharing with the NSA, CIA ... ___ Dng mailing list Dng@lists.dyne.org https://mailinglists.dyne.org/cgi-bin/mailman/listinfo/dng
Re: [DNG] strange effect on overwrite
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 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 Dng@lists.dyne.org https://mailinglists.dyne.org/cgi-bin/mailman/listinfo/dng ___ Dng mailing list Dng@lists.dyne.org https://mailinglists.dyne.org/cgi-bin/mailman/listinfo/dng
Re: [DNG] strange effect on overwrite
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 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 > Dng@lists.dyne.org > https://mailinglists.dyne.org/cgi-bin/mailman/listinfo/dng > ___ Dng mailing list Dng@lists.dyne.org https://mailinglists.dyne.org/cgi-bin/mailman/listinfo/dng
[DNG] strange effect on overwrite
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 Dng@lists.dyne.org https://mailinglists.dyne.org/cgi-bin/mailman/listinfo/dng
