How is the /home file system structured?

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The /home file systems (there is actually several of them, but they are all called /home) is the main area where our users keep their data. Each user's home directory resides there, and is called/home/hpcXXXX where hpcXXXX denotes the user name.

Physically, this file system resides in 4 racks containing approximately 1 PB of raw disk space in the form of 4 Sun "Unified Storage System" 7410 units. The building blocks of the file system consist of many RAID Z2 volumes. This configuration is designed to tolerate the failure of multiple disks without the loss of data or disruption in service. This is achieved with the implementation of a spare pool of disks. If one (or even two) member drives of an array fails, the global spare drive joins the logical drive and automatically starts to rebuild. Our disk arrays are both read and write cached through flash memory to increase speed. Access speed is homogeneous throughout the file system.

The file system is NFS at the front end and based on ZFS at the back. A high degree of redundancy is built into the system, both on the level of the headnodes (which are dual active/active), and on the level of connectivity (10 Gig Ethernet with two switches and dual cables). Part of the older SAM-QFS based storage systems serve as a backup management system that connects our disk arrays to our tape StorEdge L1400 tape library. This allows the continuous backup of files.