[sheepdog-users] Performance without cache

[Valerio Pachera]

2013/8/20 Liu Yuan <namei.unix at gmail.com>:
> How about 'dd if=/dev/zero of=c bs=1M count=512 oflag=direct,sync' in host?

The host is test004.
/mnt/sheep/dsk02 is the mount point of the mechanical disk.

root at test004:/mnt/sheep/dsk02# dd if=/dev/zero of=c bs=1M count=512 oflag=direct
512+0 record dentro
512+0 record fuori
536870912 byte (537 MB) copiati, 3,93134 s, 137 MB/s

root at test004:/mnt/sheep/dsk02# dd if=/dev/zero of=c bs=1M count=512 oflag=sync
512+0 record dentro
512+0 record fuori
536870912 byte (537 MB) copiati, 24,5683 s, 21,9 MB/s

root at test004:/mnt/sheep/dsk02# dd if=/dev/zero of=c bs=1M count=512
oflag=direct,sync
512+0 record dentro
512+0 record fuori
536870912 byte (537 MB) copiati, 23,5594 s, 22,8 MB/s

PS: giving both option (direct and sync), what kind of effect should give?
I think one of them is ignored (direct).