Am Sonntag, 7. Februar 2010 schrieb Mark Knecht: > Hi Willie, > OK - it turns out if I start fdisk using the -u option it show me > sector numbers. Looking at the original partition put on just using > default values it had the starting sector was 63 - probably about the > worst value it could be. As a test I blew away that partition and > created a new one starting at 64 instead and the untar results are > vastly improved - down to roughly 20 seconds from 8-10 minutes. That's > roughly twice as fast as the old 120GB SATA2 drive I was using to test > the system out while I debugged this issue.
Sorry if I reheat a topic that some already consider closed. I used the weekend to experiment on that stuff and need to report my results. Because they startle me a little. I first tried different start sectors around sector 63: 63, 64, 66, 68 etc. They showed nearly the same results in speed. So I almost thought that my drive, albeit being new and of high capacity, is not affected by this yet. But then I tested my main media partition, which starts in the middle of the disk. I downloaded a portage snapshot and put it into a ramdisk, so reading it would not manipulate measurements. I also copied a 1GB file into that ramdisk to test consecutive writes. As a start sector I chose 288816640, which is divisible by 64. The startling result: this gave the lowest performance. If the partition starts in one of the sectors behind it, performance was always better. I repeated the test several times to confirm it. How do you explain this? :-? The following table shows the ‘real’ value from the output of the time command. SS means the aforementioned start sector with SS % 64 == 0. action SS (1st) SS (2nd) SS+2 SS+4 SS+6 SS+8 -------------+----------+----------+----------+----------+----------+---------- untar portage 3m12.517 2m55.916 1m46.663 1m35.341 1m47.829 1m43.677 rm portage 4m11.109 3m54.950 3m18.820 3m11.378 3m21.804 3m12.433 cp 1GB file 0m21.383 0m13.558 0m14.920 0m12.813 0m13.407 0m13.681 -- Gruß | Greetings | Qapla' How are things in the collective?" - "Perfect." (Captain Jainway to the Borg queen)
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