Home > Workload Solutions > High Performance Computing > White Papers > Enhance Availability of Storage Services with an NFS Storage System > MDtest for home directory repository
One of the main use cases for this Design for NFS Storage is a home directory repository, instead of only checking metadata for empty files (not a common scenario) that only require modification of the node containing the metadata. It is useful to explore the performance for small files that require the allocation of at least one data block (minimum extra allocation). Since the data block size of the XFS file system used is 4096 (4 KiB), that is the file size selected for the metadata tests with small files.
Results from running MDtest with 4 KiB files in and contrasting the results from empty files can be found in Figure 7. As expected, being pure metadata, Stat results are barely changed, with a new slightly lower peak at 567,753 IOPs at 512 threads. Read operations start at 5,636 IOPS for one thread, rising linearly up to 16 threads, then slowly reaching a plateau with a maximum of 150,909 IOPs at 512 threads.
Creates and removals are the operations that are most affected by using 4KiB files, since they require allocating or releasing the data block that most of the time will require seek HDD operations. Create operations are the most affected, starting at about half the empty files performance for one thread with 1,437 IOPS, with an increasing drop in performance until reaching the maximum performance drop of 82.4% at 512 threads, and achieving a maximum of 15,600 IOPS at 256 threads.