NetBackup™ Commands Reference Guide

To analyze nbperfchk results and adjust the ReadBufferSize parameter setting

1. Log on as the root user (UNIX) or the administrator (Windows) on the computer that hosts the content router.

   In NetBackup environments, log on to the media server.

2. Change to a test directory.
3. Type the nbperfchk command in the following format to write a large test file to the content router:

   nbperfchk -i inputpath -o outputpath -s filesize -syncend

   For example, the following command writes a 64-GB data file that contains all zeros to the e drive:

   nbperfchk -i zero: -o e:\data1 -s 64g -syncend
   

4. Type the nbperfchk command in the following format to read the test file and observe the read speeds in the nbperfchk output:

   nbperfchk -i inputpath -o NULL -bs buffersize

   Example 1. To observe several read speeds with several buffer sizes, type the following series of commands:

   nbperfchk -i e:\data1 -bs 64k -o NULL
   nbperfchk -i e:\data1 -bs 128k -o NULL
   nbperfchk -i e:\data1 -bs 256k -o NULL

   Example 2. The following nbperfchk command reads back the data in file data1 and uses a buffer size of 1024 KB:

   C:\Users\administrator.mymediaserver\Desktop>nbperfchk -i e:\data1 -bs 1024k -o NULL
        195 MB @   65.3 MB/sec,      194 MB @   64.9 MB/sec
        295 MB @   49.4 MB/sec,      100 MB @   33.5 MB/sec
        403 MB @   44.8 MB/sec,      108 MB @   35.8 MB/sec
        505 MB @   42.1 MB/sec,      102 MB @   34.1 MB/sec
        599 MB @   40.0 MB/sec,       94 MB @   31.3 MB/sec
        705 MB @   39.2 MB/sec,      106 MB @   35.5 MB/sec
        821 MB @   39.2 MB/sec,      116 MB @   38.8 MB/sec
        943 MB @   39.4 MB/sec,      122 MB @   40.8 MB/sec
       1024 MB @   40.1 MB/sec

   Observe the following when you analyze the data:

   • The left two columns show the amount of data read and the average read speed.

     For the bolded information in the example shown, the amount of data read is 403 MB. The average read speed is 44.8 MB/sec.

   • The right two columns show the average read speed in the last 3 seconds of each read.

     For the bolded information in the example shown, the average amount of data that was read in the last three seconds is 108 MB. The average read speed for the last three seconds is 35.8 MB/sec.

     Unless these numbers vary drastically from read to read, you can disregard the right two columns.

   • The final line shows the overall read speed.

     In the example shown, final line is the 1024 MB @ 40.1 MB/sec information. In this example, the overall read speed for this test is 40.1 MB/sec.

     This line is the most important line in the output because it shows you how fast the total read occurred with the buffer size you specified.

5. Analyze your read speeds and adjust the ReadBufferSize parameter if necessary.

   Your operating system, your disk speeds, and the ReadBufferSize parameter setting all affect restore and rehydration performance.

   Cohesity recommends that you type several nbperfchk commands and increase the size of the argument to the -bs parameter each time. Example 1 in step 4 shows this method. If you can enter ever-increasing arguments to the -bs parameter, you can probably increase the size of the ReadBufferSize parameter in the [CRDataStore] section of the contentrouter.cfg file.

   By default, ReadBufferSize=65536, which is 64K. Cohesity testing shows that ReadBufferSize=1048576, which is 1024 X 1024, or 1M, offers good performance on most Windows systems. On most UNIX systems, Cohesity testing shows that ReadBufferSize=65536 (the default) offers good performance.

   For information about how to edit NetBackup configuration files, see the NetBackup documentation.