Date: Thu, 8 Mar 2007 00:06:14 +0300 From: "Artem Kuchin" <matrix@itlegion.ru> To: "Fluffles" <etc@fluffles.net> Cc: freebsd-stable@freebsd.org Subject: Re: Some Unix benchmarks for those who are interesed Message-ID: <007901c760fc$71e708a0$0c00a8c0@Artem> References: <20070306020826.GA18228@nowhere> <45ECF00D.3070101@samsco.org><20070306050312.GA2437@nowhere><008101c75fcc$210c74a0$0c00a8c0@Artem> <esk9vq$uhh$1@sea.gmane.org><001a01c7601d$5d635ee0$0c00a8c0@Artem> <eskka8$adn$1@sea.gmane.org><001801c7603a$5339e020$0c00a8c0@Artem> <eskpd1$sm4$1@sea.gmane.org> <20070307105144.1d4a382f@daydream.goid.lan><002801c760e2$5cb5eb50$0c00a8c0@Artem> <esmvnp$khs$1@sea.gmane.org><005b01c760e6$9a798bf0$0c00a8c0@Artem> <esn2s6$1i9$1@sea.gmane.org> <001601c760ee$f76fa300$0c00a8c0@Artem> <45EF2215.2080402@fluffles.net>
next in thread | previous in thread | raw e-mail | index | archive | help
----- Original Message ----- From: "Fluffles" <etc@fluffles.net> To: "Artem Kuchin" <matrix@itlegion.ru> Sent: Wednesday, March 07, 2007 11:35 PM Subject: Re: Some Unix benchmarks for those who are interesed > Artem Kuchin wrote: >>>> Artem Kuchin wrote: >>>> Hmm. what kind of HDD, RAID or whatever are you using? >>>> My raid pretty much sucks. It is build it on the intel motherboard >>>> LSI Megaraid. But i still get 81Mb/sec when doing >>>> dd if=/dev/ar0 of=/dev/null bs=1M >>>> >>>> How much do you get on this? >>> >>> geom_mirror on 2 desktop SATA drives, but the results of dd are >>> pretty low: >>> >>> # dd if=/dev/mirror/data of=/dev/null bs=1m count=1000 >>> 1000+0 records in >>> 1000+0 records out >>> 1048576000 bytes transferred in 17.817686 secs (58850290 bytes/sec) >>> >>> As you can see, results with a single drive are better: >>> >>> # dd if=/dev/ad4 of=/dev/null bs=1m count=1000 >>> 1000+0 records in >>> 1000+0 records out >>> 1048576000 bytes transferred in 16.219518 secs (64649023 bytes/sec) >> >> How is it possible that you get 2x file copy perfomance ? What's the >> matter?! > > If you use dd on the raw device (meaning no UFS/VFS) there is no > read-ahead. This means that the following DD-command will give lower STR > read than the second: > > no read-ahead: > dd if=/dev/mirror/data of=/dev/null bs=1m count=1000 > read-ahead and multiple I/O queue depth: > dd if=/mounted/mirror/volume of=/dev/null bs=1m count=1000 > > You can test read STR best with bonnie (see > /usr/ports/benchmarks/bonnie); or just with DD on a mounted volume. You > should mount with -o noatime to avoid useless writes during reading, or > use soft updates to prevent meta data from taking it's toll on I/O > performance. > Totall disagree. On the following reasons: 1) Read ahead is simply useless when stream-reading (sequential) 1GB of data 2) atime is NOT updated when using dd on any device, atime is related to file/inode operations which are not performed by dd 3) soft update are also useless (no bad, no good) for long sequential read basically, long sequatial reads/write ignore anything but real drive speed (plate on the spindle) if they are performed long enough. I think that 2 times differences is reallty related to seek times. But on the other hand i am sure my HDD have very good seek times. I'll have a chance to check it all on friday. -- Artem
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?007901c760fc$71e708a0$0c00a8c0>