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. 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
