GFS2 學習

一 mount選項使用noatime與nodiratime

這樣會更快。

2.5.1. Mount Options: noatime and nodiratime
It is generally recommended to mount GFS2 file systems with the noatime and nodiratime arguments. This allows GFS2 to spend less time updating disk inodes for every access. For more information on the effect of these arguments on GFS2 file system performance, see Section 2.9, 「GFS2 Node Locking」.
https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/7/html/global_file_system_2/s1-usage-gfs2#s2-recommendedmount-gfs2

二 NFS的相關考慮

(1) 只支持active/passive模式
2.5.4. Setting Up NFS Over GFS2
Red Hat supports only Red Hat High Availability Add-On configurations using NFSv3 with locking in an active/passive configuration with the following characteristics:

(2) 只能從集羣的單一節點訪問，或者說只支持單虛擬IP。即便是多虛擬IP， 這些IP也只能在一個節點上。
An NFSv3 server is defined as a service exporting the entire GFS2 file system from a single cluster node at a time.

The NFS server can fail over from one cluster node to another (active/passive configuration).

三 不支持NFS/Samba混合使用，也不支持對GFS2的本地操做。因此須要把CTDB, Pacemaker的共享文件放在獨立的GFS2上，而不是放在Nas共享的GFS2上。
No access to the GFS2 file system is allowed except through the NFS server. This includes both local GFS2 file system access as well as access through Samba or Clustered Samba.

四 不支持NFS quota
There is no NFS quota support on the system.

五 NFS的導出中須要加入fsid=NFS
The fsid= NFS option is mandatory for NFS exports of GFS2.

另外：若是要實現NFS高可用，必須配置fsid。這句話來源於下面文章。

https://blog.csdn.net/younger_china/article/details/52981675

六 Samba支持active/active模式，但對samba共享的數據禁止samba以外的方式接入。2.5.5. Samba (SMB or Windows) File Serving Over GFS2You can use Samba (SMB or Windows) file serving from a GFS2 file system with CTDB, which allows active/active configurations. Simultaneous access to the data in the Samba share from outside of Samba is not supported. 七 若是使用reboot來重啓機器而沒有umount GFS2文件系統，會致使機器掛起。若是使用pacemaker管理GFS2的mount，在重啓時，pacemaker會自動umount掉GFS2。若是是手動mount GFS2，重啓前務必umount GFS2，不然reboot不起做用，只能硬重啓。GFS2 file systems that have been mounted manually rather than automatically through Pacemaker will not be known to the system when file systems are unmounted at system shutdown. As a result, the GFS2 script will not unmount the GFS2 file system. After the GFS2 shutdown script is run, the standard shutdown process kills off all remaining user processes, including the cluster infrastructure, and tries to unmount the file system. This unmount will fail without the cluster infrastructure and the system will hang.  To prevent the system from hanging when the GFS2 file systems are unmounted, you should do one of the following:    Always use Pacemaker to manage the GFS2 file system. For information on configuring a GFS2 file system in a Pacemaker cluster, see Chapter 5, Configuring a GFS2 File System in a Cluster.    If a GFS2 file system has been mounted manually with the mount command, be sure to unmount the file system manually with the umount command before rebooting or shutting down the system. If your file system hangs while it is being unmounted during system shutdown under these circumstances, perform a hardware reboot. It is unlikely that any data will be lost since the file system is synced earlier in the shutdown process. https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/7/html/global_file_system_2/s1-mount-considerations