On 15/01/2013 3:03 PM, Dieter BSD wrote:
Disabling the disks's write cache is *required* for data integrity. One op per rev means write caching is disabled and no queueing. But dmesg claims "Command Queueing enabled", so you should be getting more than one op per rev, and writes should be fast. Is this dd to the raw drive, to a filesystem? (FFS? ZFS? other?) Are you running compression, encryption, or some other feature that might slow things down? Also, try dd with a larger block size, like bs=1m.
Hi,
Thanks to everyone that answered so far. Here is a follow up. dd to the raw drive and no compression/encryption or some other features, just a naive boot off a live 9.1 CD then dd (see below). The following results have been gathered on the FreeBSD 9.1 system:
# dd if=/dev/zero of=toto count=100 100+0 records in 100+0 records out 51200 bytes transferred in 1.057507 secs (48416 bytes/sec) # dd if=/dev/zero of=toto count=100 bs=104 100+0 records in 100+0 records out 10400 bytes transferred in 1.209524 secs (8598 bytes/sec) # dd if=/dev/zero of=toto count=100 bs=1024 100+0 records in 100+0 records out 102400 bytes transferred in 0.844302 secs (121284 bytes/sec) # dd if=/dev/zero of=toto count=100 bs=10240 100+0 records in 100+0 records out 1024000 bytes transferred in 2.173532 secs (471123 bytes/sec) # dd if=/dev/zero of=toto count=100 bs=102400 100+0 records in 100+0 records out 10240000 bytes transferred in 19.915159 secs (514181 bytes/sec) # dd if=/dev/zero of=toto count=100 100+0 records in 100+0 records out 51200 bytes transferred in 1.070473 secs (47829 bytes/sec) # dd if=/dev/zero of=foo count=100 100+0 records in 100+0 records out 51200 bytes transferred in 0.683736 secs (74883 bytes/sec) # dd if=/dev/zero of=foo count=100 bs=1024 100+0 records in 100+0 records out 102400 bytes transferred in 0.682579 secs (150019 bytes/sec) # dd if=/dev/zero of=foo count=100 bs=10240 100+0 records in 100+0 records out 1024000 bytes transferred in 2.431012 secs (421224 bytes/sec) # dd if=/dev/zero of=foo count=100 bs=102400 100+0 records in 100+0 records out 10240000 bytes transferred in 19.963030 secs (512948 bytes/sec) # dd if=/dev/zero of=foo count=10 bs=1024000 10+0 records in 10+0 records out 10240000 bytes transferred in 19.615134 secs (522046 bytes/sec) # dd if=/dev/zero of=foo count=1 bs=10240000 1+0 records in 1+0 records out 10240000 bytes transferred in 19.579077 secs (523007 bytes/sec) Best regards, Karim. _______________________________________________ [email protected] mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-hackers To unsubscribe, send any mail to "[email protected]"
