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ShaoLin InfiniCluster Cluster allow all data to stored only on the shared storage and able to operate without any local or internal storage devices. The consideration and requirements of using local disks depends on your need on cluster operations and administration. Local disks are recommended to use as swap disks, since swap data are temporary data which is not important to share among the clusters. However, there are couple of reason to use local disks or not
Using local storage allow you to spread the load on the shared storage in case of swap. Swapping to local disk avoid the I/O traffic going to the shared storage. Since local storage and external shared storage locate on a different I/O path, this will improve performance significantly in low memory systems
Another advantage to have local disks is to allow on-line upgrade the clusters without taking down the system. Some Linux distribution installation process will automatically wake up detected swap partitions during the OS installation phase. If this happens while the ACTIVE NODE is in production during the installation or new OS on the STANDBY NODE, it is dangerous and may cause memory corruption of the production cluster. If you are using internal swap partitions, you are safe to install a new operating system on an unused shared volume to perform OS installation without interference of the clusters.
It is recommended to use RAID-1 on local disk drives to eliminate the single point of failure of the swap partitions.
Using internal disk drives can gain performance and flexibility. On the down side, managing diskless servers can gain advantages of reducing chance of failure. Running an additional disk array for each cluster can increase the chance of failure and added load to system administration.
For absolute reliability and manageability, using internal disks is not recommended.