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4.1.3 Using ``tar'' to unpack files

Trying to measure the write performance of real applications we used the Unix tar command used to unpack many files from a single archive. We must note that tar does not compress the files, it simply packs a whole directory tree into a single file. As a test file we used the sources of Gnu Compiler version 2.7.2, a popular package used in most Unix machines. The directory tree contained in the tarfile was 28 MBytes in size, and had 1075 files. We timed the command to unpack the archive file into the Network RamDisk and the magnetic disk. Table 3 presents the results. Thus the application is 79% faster on the NRD, than on the magnetic disk. This performance advantage can be exploited by many applications which do many sequential file writes, such as visualizing tools, proxies and databases.



Figure 8: 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 file creates.The latency shown is the number of milliseconds (ms) per file creation 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.

Mike Flouris
Thu Sep 17 18:12:15 EET DST 1998