|FS_GETSERVERPREFS(1)||AFS Command Reference||FS_GETSERVERPREFS(1)|
fs_getserverprefs - Displays preference ranks for file servers or VL servers
[-file <output to named file>]
[-numeric] [-vlservers] [-help]
fs gets [-f <output to named file>] [-n] [-v] [-h]
fs gp [-f <output to named file>] [-n] [-v] [-h]
The fs getserverprefs command displays preference ranks for file server machine interfaces (file server machines run the fs process) or, if the -vlserver flag is provided, for Volume Location (VL) Server machines (which run the vlserver process). For file server machines, the Cache Manager tracks up to 15 interfaces per machine and assigns a separate rank to each interface. The ranks indicate the order in which the local Cache Manager attempts to contact the interfaces of machines that are housing a volume when it needs to fetch data from the volume. For VL Server machines, the ranks indicate the order in which the Cache Manager attempts to contact a cell's VL Servers when requesting VLDB information. For both types of rank, lower integer values are more preferred.
The Cache Manager stores ranks in kernel memory. Once set, a rank persists until the machine reboots, or until the fs setserverprefs command is used to change it. fs_setserverprefs(1) explains how the Cache Manager sets default ranks, and how to use that command to change the default values.
Default VL Server ranks range from 10,000 to 10,126. The Cache Manager assigns ranks to every machine listed in its copy of the /etc/openafs/CellServDB file or found via DNS AFSDB or SRV records for the cell when it initializes. When the Cache Manager needs to fetch VLDB information from a cell, it compares the ranks for the VL Server machines belonging to that cell, and attempts to contact the VL Server with the lowest integer rank. If the Cache Manager cannot reach the VL Server (because of server process, machine or network outage), it tries to contact the VL Server with the next lowest integer rank, and so on. If all of a cell's VL Server machines are unavailable, the Cache Manager cannot fetch data from the cell.
Default file server ranks range from 5,000 to 40,000, excluding the range used for VL Servers (10,000 to 10,126); the maximum possible rank is 65,534. When the Cache Manager needs to fetch data from a volume, it compares the ranks for the interfaces of machines that house the volume, and attempts to contact the interface that has the lowest integer rank. If it cannot reach the fileserver process via that interface (because of server process, machine or network outage), it tries to contact the interface with the next lowest integer rank, and so on. If it cannot reach any of the interfaces for machines that house the volume, it cannot fetch data from the volume.
For both file server machines and VL Server machines, it is possible for a machine or interface in a foreign cell to have the same rank as a machine or interface in the local cell. This does not present a problem, because the Cache Manager only ever compares ranks for machines belonging to one cell at a time.
- -file <output file>
- Specifies the full pathname of a file to which to write the preference ranks. If the specified file already exists, the command overwrites its contents. If the pathname is invalid, the command fails. If this argument is not provided, the preference ranks appear on the standard output stream.
- Displays the IP addresses of file server machine interfaces or VL Server machines, rather than their hostnames. If this argument is not provided, the fs command interpreter has the IP addresses translated to hostnames such as "fs1.example.com".
- Displays preference ranks for VL Server machines rather than file server machine interfaces.
- Prints the online help for this command. All other valid options are ignored.
The output consists of a separate line for each file server machine interface or VL Server machine, pairing the machine's hostname or IP address with its rank. The Cache Manager stores IP addresses in its kernel list of ranks, but the command by default identifies interfaces by hostname, by calling a translation routine that refers to either the cell's name service (such as the Domain Name Server) or the local host table. If an IP address appears in the output, it is because the translation attempt failed. To bypass the translation step and display IP addresses rather than hostnames, include the -numeric flag. This can significantly speed the production of output.
By default, the command writes to the standard output stream. Use the -file argument to write the output to a file instead.
The following example displays the local Cache Manager's preference ranks for file server machines. The local machine belongs to the AFS cell named example.com, and in this example the ranks of file server machines in its local cell are lower than the ranks of file server machines from the foreign cell, "example.net". It is not possible to translate the IP addresses of two machines on the 138.255 network.
% fs getserverprefs fs2.example.com 20007 fs3.example.com 30002 fs1.example.com 20011 fs4.example.com 30010 server1.example.net 40002 126.96.36.199 40000 server6.example.net 40012 188.8.131.52 40005
The following example shows hows the output displays IP addresses when the -numeric flag is included, and illustrates how network proximity determines default ranks (as described on the fs setserverprefs reference page). The local machine has IP address 184.108.40.206, and the two file server machines on its subnetwork have ranks of 20,007 and 20,011. The two file server machines on a different subnetwork of the local machine's network have higher ranks, 30,002 and 30,010, whereas the ranks of the remaining machines range from 40,000 to 40,012 because they are in a completely different network.
% fs getserverprefs -numeric 220.127.116.11 20007 18.104.22.168 30002 22.214.171.124 20011 126.96.36.199 30010 188.8.131.52 40002 184.108.40.206 40000 220.127.116.11 40012 18.104.22.168 40005
The example shows how the -vlservers flag displays preference ranks for VL Server machines:
% fs getserverprefs -vlservers fs2.example.com 10052 fs3.example.com 10113 fs1.example.com 10005
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