Client Node Tuning

Parallel Network Requests

Each BeeGFS client establishes multiple network connections to the same server, which allows the client to have multiple network requests in flight to this server. The number of connections from a particular client to the same server can be configured by setting the value of connMaxInternodeNum in /etc/beegfs/beegfs-client.conf.

Increasing the number of connections may improve performance and responsiveness for certain workloads. When increasing the value, it is extremely important to keep the resulting RAM usage for network buffers on the servers in mind, especially for InfiniBand and larger cluster setups. Make sure to read the comments for connMaxInternodeNum and connRDMABufSize in beegfs-client.conf to learn more about the server-side RAM usage. Note that connRDMABufSize needs to be an integer multiple of 4 KiB. On a compute node, it usually doesn’t make sense to set this number higher than the number of CPU cores. On a cluster login node, setting this value higher than the number of CPU cores may help to improve responsiveness when multiple users are active.

BeeGFS clients establish connections only when they are needed (and drop them after some idle time). Use the command beegfs-net on a client to see the number of currently established connections to each of the servers. beegfs-net is contained in the beegfs-utils package. The total space used by the buffers (connRDMABufSize x connRDMABufNum) should be larger or equal to the data chunk size, so that the messages exchanged between client and storage servers do not need to be split to fit into the buffers available. The default RDMA settings (connRDMABufSize = 65536 ``, ``connRDMABufNum = 12) are OK for the default chunk size of 512 KB. If you set a chunk size of 1 MB and a buffer size of 65536, the number of buffers should be at least 1 MB / 64 KB + 4 additional buffers for protocol, so 20 in this example.

Remote fsync

BeeGFS clients have a configuration option to control behavior when a user application calls fsync(). The option is called tuneRemoteFSync in /etc/beegfs/beegfs-client.conf. The client can either enforce that data is committed to the server disks on fsync() (tuneRemoteFSync=true) or only make sure that data is transferred to the server-side cache (tuneRemoteFSync=false). Disabling remote fsync can significantly reduce disk seeks and thus improves performance for applications that use a lot of fsync() calls.

Disable locate/mlocate/updatedb

Some Linux distributions install a locate tool which scans all file systems once per day to build a database of existing files. These tools can create unnecessary load on the filessytem if they are active on the client nodes. Either deactivate this service if you don’t need it or edit the file /etc/updatedb.conf to make sure that the beegfs file system type is contained in the PRUNEFS list and your BeeGFS mount point is contained in the PRUNEPATHS list.

Communication retries

BeeGFS clients support a time-limited retry mode for communications, which will make them keep on trying to complete their I/O operation in case a server is temporarily unreachable. The connCommRetrySecs option in /etc/beegfs/beegfs-client.conf sets the time limit for communication retries. Retries can be stopped by:

  • Interrupting the application waiting for the I/O operation, e.g. CTRL + c.

  • Disabling retries for the entire mountpoint: echo false > /proc/fs/beegfs/<...>/conn_retries_enabled

Preferred servers

Clients can prefer certain storage servers for new files and directories. For example, due to a certain network topology. See options tunePreferredMetaFile and tunePreferredStorageFile in /etc/beegfs/beegfs-client.conf. Note: These options only affect the placement of new files. Clients having those options can set still read all files, regardless on which server they are located.