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Dell HPC NFS Storage Solution - High Availability (NSS6.0-HA) Configuration with Dell PowerEdge 13
th
Generation Servers
22
A.2. Checkstream
The checkstream utility is available at http://sourceforge.net/projects/checkstream/. Version 1.0
was installed and compiled on the NFS servers and used for these tests.
First, a large file was created using the genstream utility. This file was copied to and from the NFS
share by each client using dd to mimic write and read operations. Failures were simulated during the
file copy process and the NFS service was failed over from one server to another. The resultant output
files were checked using the checkstream utility to test for data correctness and ensure that there
was no data corruption.
Below is a sample output of a successful test with no data corruption.
checkstream[genstream.file.100G]: ------------------------------------------------
checkstream[genstream.file.100G]: valid data for 107374182400 bytes at offset 0
checkstream[genstream.file.100G]: ------------------------------------------------
checkstream[genstream.file.100G]: end of file summary
checkstream[genstream.file.100G]: [valid data] 1 valid extents in 261.205032
seconds (0.00382841 err/sec)
checkstream[genstream.file.100G]: [valid data] 107374182400/107374182400 bytes (100
GiB/100 GiB)
checkstream[genstream.file.100G]: read 26214400 blocks 107374182400 bytes in
261.205032 seconds (401438 KiB/sec), no errors
For comparison, here is an example of a failing test with data corruption in the copied file. For
example, if the file system is exported via the NFS async operation and there is an HA service failover
during a write operation, data corruption is likely to occur.
checkstream[compute-00-10]: ------------------------------------------------
checkstream[compute-00-10]: valid data for 51087769600 bytes at offset 45548994560
checkstream[compute-00-10]:
checkstream[compute-00-10]: ------------------------------------------------
checkstream[compute-00-10]: end of file summary
checkstream[compute-00-10]: [valid data] 1488 valid extents in 273.860652 seconds
(5.43342 err/sec)
checkstream[compute-00-10]: [valid data] 93898678272/96636764160 bytes (87 GiB/90
GiB)
checkstream[compute-00-10]: [zero data] 1487 errors in 273.860652 seconds (5.42977
err/sec)
checkstream[compute-00-10]: [zero data] 2738085888/96636764160 bytes (2 GiB/90 GiB)
checkstream[compute-00-10]: read 23592960 blocks 96636764160 bytes in 273.860652
seconds (344598 KiB/sec)
checkstream[compute-00-10]: ------------------------------------------------
checkstream[compute-00-10]: encountered 1487 errors, failing
A.3. The dd Linux utility
dd is a Linux utility provided by the coreutils rpm distributed with RHEL 7.0. It was used to copy a file.
The NFS file system was mounted at /mnt/xfs on the clients.
To write data to the storage, the following command line was used.