On Mar 6, 2011, at 6:49 PM, Chris Murphy wrote: > Anyone have any idea why I'm getting a 6x difference in performance between > two OS's on the exact same hardware? > > /dev/disk0 and /dev/sda are the exact same internal SATA drive.
Do you have the linux disk mounted async? My understanding is that linux does that by default while most other OSes do not. Or something like that. What file system is on the linux side? > > > Mac OS X 10.6.5: > > mingisapsycho:~ chris$ sudo dd if=/dev/disk0 of=/dev/zero bs=256k count=3814 > Password: > 3814+0 records in > 3814+0 records out > 999817216 bytes transferred in 56.340225 secs (17746064 bytes/sec) > > Fedora 14: > > [chris@macbook ~]$ sudo dd if=/dev/sda of=/dev/zero bs=256k count=3814 > 3814+0 records in > 3814+0 records out > 999817216 bytes (1.0 GB) copied, 9.30449 s, 107 MB/s > > > If I repeat the commands a second time without rebooting, I get: > > Mac OS: > 999817216 bytes transferred in 55.951727 secs (17869282 bytes/sec) > > Fedora: > 999817216 bytes (1.0 GB) copied, 0.312232 s, 3.2 GB/s > > So clearly Fedora is caching the entire 1GB into RAM and Mac OS X is not > caching at all. But is there some DMA + tagged queuing that Linux could be > doing that Mac OS X is not? Or is there something hosed with dd on Mac OS X? > Anecdotally I get similar performance differences between local file > duplication whether it's Finder vs Nautilus or cp vs cp. So I'm not > understanding what could explain such a massive difference. I get similar > numbers for write performance as well. > > Chris Murphy_______________________________________________ > MacOSX-admin mailing list > [email protected] > http://www.omnigroup.com/mailman/listinfo/macosx-admin _______________________________________________ MacOSX-admin mailing list [email protected] http://www.omnigroup.com/mailman/listinfo/macosx-admin
