To measure the I/O Latency of the Network RamDisk
and compare it with the disk,
we ran a microbenchmark program called lat_fs which
is part of the HBench-OS Benchmark Suite 
.
Lat_fs measures the latency of performing certain file
system metadata operations, in particular file creates
and deletes. We ran the benchmark both for 2000 file creations
and deletions, with variable file size. The resulting graphs
are depicted in Figures 8 and 9. We see
that the latency advantage of the Network RamDisk makes
the performance improvement for this benchmark very high.
For example for 2000 file creations of 16 KBytes each,
the creation time for each file on the magnetic disk is
equal to 116.22 milliseconds (or 8.60 files per second),
whereas on the Network RamDisk the creation time is
22.68 milliseconds (or 44.09 files per second).
This is a 412% real time improvement for
a 16 KByte file creation.
Figure 9: Comparison of the I/O Latency performance of Magnetic
Disk vs. Network RamDisk, using HBench-OS:
This test measures the latency of performing certain file
system metadata operations, in particular random file deletes.The
latency shown is the number of milliseconds (ms) per file
deletion for a total of 2000 on each of the devices.
The benchmark were executed from user level on the DEC-Alpha 3000 model 300
with 32MB of main memory running Digital Unix 4.0, and
compiled with the standard system C compiler (cc).
The Network RamDisk used as servers two DEC-Alpha 3000
model 300 workstations, each with 32 MBytes of main memory.
Figure 10: Comparison of Sequential File I/O on
either the disk, or the Network RamDisk:
In this test we measured the performance of
Sequential File I/O, using a microbenchmark
called IOZONE, V2.01 by Bill Norcott. We see that
the use of remote memory results in significantly higher
sequential file I/O performance compared to the magnetic disk.
All benchmarks were run on a DEC-Alpha 3000 model 300 workstation,
under Digital Unix 4.0. The Network RamDisk used as servers two DEC-Alpha 3000
model 300 workstations, each with 32 MBytes of main memory.
