Messages in this thread | | | From | Bill Davidsen <> | Subject | Re: Abysmal disk performance, how to debug? | Date | Sat, 27 Jan 2007 14:43:04 -0500 |
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Willy Tarreau wrote: > On Sat, Jan 20, 2007 at 02:56:20PM -0500, Stephen Clark wrote: >> Sunil Naidu wrote: >> >>> On 1/20/07, Willy Tarreau <w@1wt.eu> wrote: >>> >>> >>>> It is not expected to increase write performance, but it should help >>>> you do something else during that time, or also give more responsiveness >>>> to Ctrl-C. It is possible that you have fast and slow RAM, or that your >>>> video card uses shared memory which slows down some parts of memory >>>> which are not used anymore with those parameters. >>>> >>>> >>> I did test some SATA drives, am getting these value for 2.6.20-rc5:- >>> >>> [sukhoi@Typhoon ~]$ time dd if=/dev/zero of=/tmp/1GB bs=1M count=1024 >>> 1024+0 records in >>> 1024+0 records out >>> 1073741824 bytes (1.1 GB) copied, 21.0962 seconds, 50.9 MB/s >>> >>> What can you suggest here w.r.t my RAM & disk? >>> >>> >>> >>>> Willy >>>> >>>> >>> Thanks, >>> >>> ~Akula2 >>> - >>> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in >>> the body of a message to majordomo@vger.kernel.org >>> More majordomo info at http://vger.kernel.org/majordomo-info.html >>> Please read the FAQ at http://www.tux.org/lkml/ >>> >>> >>> >> Hi, >> whitebook vbi s96f core 2 duo t5600 2gb hitachi ATA HTS721060G9AT00 >> using libata >> time dd if=/dev/zero of=/tmp/1GB bs=1M count=1024 >> 1024+0 records in >> 1024+0 records out >> 1073741824 bytes (1.1 GB) copied, 10.0092 seconds, 107 MB/s >> >> real 0m10.196s >> user 0m0.004s >> sys 0m3.440s > > You have too much RAM, it's possible that writes did not complete before > the end of your measurement. Try this instead : > > $ time dd if=/dev/zero of=/tmp/1GB bs=1M count=1024 | sync > I'm not sure that does what you think it does, the sync runs first, and data is still in the cache. Replace sync with "/bin/echo RAN" if you doubt me.
What you want is this: sync; time bash -c "dd if=/dev/zero of=/tmp/1GB bs=1M count=1024; sync" which will actually time the write with the time command.
-- Bill Davidsen <davidsen@tmr.com> "We have more to fear from the bungling of the incompetent than from the machinations of the wicked." - from Slashdot
- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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