idallen@watcgl.waterloo.edu (10/20/89)
From: "Ian! D. Allen [CGL]" <idallen>
On an 8-Meg VAXstation 3100 running Ultrix 3.0 I created a 10Meg file and
then did:
# time dd if=in of=out bs=1024k
in the root mount point of each of the two internal rz23 disks and then
in the root mount point of the external rz55 disk. The rz23 took about a
minute of real time. The rz55 consistently took 10-15 seconds longer.
Why? All disks have the same block/frag size. The specifications of the
rz55 suggest it should be faster. The rz23's were about as fast for
this copy as our ra82's on our 8600 under 4.3bsd. In fact, the rcp of
the file from the 3100 to the 8600 was slightly faster than either
of the disk-to-disk copy's.alan@shodha.dec.com ( Alan's Home for Wayward Notes File.) (10/21/89)
In article <12001@watcgl.waterloo.edu>, idallen@watcgl.waterloo.edu writes: > From: "Ian! D. Allen [CGL]" <idallen> > > On an 8-Meg VAXstation 3100 running Ultrix 3.0 I created a 10Meg file and > then did: > > # time dd if=in of=out bs=1024k > > The rz23 took about a minute of real time. The rz55 consistently > took 10-15 seconds longer. > Why? As shipped the RZ23 has a read-ahead cache which is enabled. The RZ55 also has a read-ahead cache, but it isn't enabled. Hopefully a future version of rzdisk(8) will support turning on the read-ahead cache of the RZ55. Till then, I don't how or even if it can be done. -- Alan Rollow alan@nabeth.enet.dec.com