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Veritas NetBackup™ Virtual Appliance Documentation

Last Published: 2017-07-25

Product(s): Appliances (3.0)

Name

Main > Support > nbperfchk — Measures a disk array's read and write speeds.

SYNOPSIS

nbperfchk -i inputpath -o outputpath [-s filesize] [-syncend] [-bs buffersize]

DESCRIPTION

The nbperfchk command measures the read speed and write speed of a disk array. You can use this command to test the read speed and the write speed of the disks that host deduplicated data. For example, you can measure the speeds of the disks that host deduplicated data as follows:

In a PureDisk storage pool, use this command to measure the speed of disks attached to the content router.
In a NetBackup media server deduplication pool (MSDP), use this command to measure the speed of the disks attached to the media server. The media server can be running any operating system that Veritas supports for media servers and MSDPs.

Note:

Veritas recommends that you work with a Veritas Technical Support staff member when you run this command and interpret its results. Veritas recommends a minimum disk performance level of 130 MB/sec for deduplicated read and write operations.

The nbperfchk command is functionally equivalent to the obsolete camel command that was available from Veritas as a downloadable program but was not associated with any specific product release. The camel command is available internally from the Veritas Technical Support website as HOWTO47457.

The nbperfchk utility enables you to write a test file to a disk, read back that test file, and observe the read speeds attained during the read operation. You can use the results from nbperfchk to make sure that the ReadBufferSize parameter is set appropriately in your backup environment. The ReadBufferSize parameter resides in the [CRDataStore] section of the contentrouter.cfg file. You can use this command as follows:

Use the following command to write data to the disks:
nbperfchk -i inputpath -o outputpath -s filesize -syncend
Use the following command to read data from the disks:
nbperfchk -i inputpath -o outputpath -bs buffersize

OPTIONS

-i inputpath

For inputpath, specify the full path to an input file. The nbperfchk command reads this file and generates information about the read speed when this file is read to disk.

For example, you can specify the following to read in a file that contains all zero characters (0x00) from the /dev/zero:

-o outputpath

For outputpath, specify the full path to an output file. The nbperfchk command creates this file.

For example, on writes, specify the path to the output file that you want to create. On reads, specify -o NUL to discard all the output as it is generated.

-s filesize

For filesize, specify a file size that is equal to or larger than than combined memory size of your computer plus the amount in the disk array. A file of this size ensures that the data is written to disk and not to a buffer.

-syncend

The syncend parameter flushes the buffer and writes all data to disk.

-bs buffersize

For buffersize, specify the read buffer size to use when nbperfchk runs. For example, 64k or 128k.

PROCEDURES

To analyze nbperfchk results and adjust the ReadBufferSize parameter setting

Log in as the root user (UNIX) or the administrator (Windows) on the computer that hosts the content router.
In PureDisk environments, log into the storage pool authority node or storage pool authority appliance.
In NetBackup environments, log into the media server.
Change to a test directory.
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
```
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 NUL -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 NUL
nbperfchk -i e:\data1 -bs 128k -o NUL
nbperfchk -i e:\data1 -bs 256k -o NUL
```
Example 2. The following nbperfchk command reads back the data in file data1 and uses a buffer size of 1024 K:
```
C:\Users\administrator.mymediaserver\Desktop>nbperfchk -i e:\data1 -bs 1024k -o NUL
     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.
- The final line shows the overall read speed. This is the most important line in this output because it shows you how fast the total read occurred with the buffer size you specified.
- The right two columns show the average read speed in the last 3 seconds of each read. Unless these numbers vary drastically from read to read, you can disregard the right two columns.
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.
Veritas 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. Veritas testing shows that ReadBufferSize=1048576, which is 1024 X 1024, or 1M, offers good performance on most Windows systems. On most UNIX systems, Veritas testing shows that ReadBufferSize=65536 (the default) offers good performance.
For information about how to edit NetBackup configuration files, see your NetBackup documentation.
For information about how to edit PureDisk configuration files, see the PureDisk Administrator's Guide.