Marko Milisavljevic wrote:
> To reply to my own message.... this article offers lots of insight into why
> dd access directly through raw disk is fast, while accessing a file through
> the file system may be slow.
>
> http://www.informit.com/articles/printerfriendly.asp?p=606585&rl=1
>
> So, I guess what I'm wondering now is, does it happen to everyone that ZFS is
> under half the speed of raw disk access? What speeds are other people getting
> trying to dd a file through zfs file system? Something like
>
> dd if=/pool/mount/file of=/dev/null bs=128k (assuming you are using default
> ZFS block size)
>
> how does that compare to:
>
> dd if=/dev/dsk/diskinzpool of=/dev/null bs=128k count=10000
>
>
Testing on a old Athlon MP box, two U160 10K SCSI drives.
bash-3.00# time dd if=/dev/dsk/c2t0d0 of=/dev/null bs=128k count=10000
10000+0 records in
10000+0 records out
real 0m44.470s
user 0m0.018s
sys 0m8.290s
time dd if=/test/play/sol-nv-b62-x86-dvd.iso of=/dev/null bs=128k
count=10000
10000+0 records in
10000+0 records out
real 0m22.714s
user 0m0.020s
sys 0m3.228s
zpool status
pool: test
state: ONLINE
scrub: none requested
config:
NAME STATE READ WRITE CKSUM
test ONLINE 0 0 0
mirror ONLINE 0 0 0
c2t0d0 ONLINE 0 0 0
c2t1d0 ONLINE 0 0 0
Ian
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