Figure 6-2shows part of array of mappings for block n. In this example, ckpti+1 is the most recent checkpoint and thus, the last entry in the mappings and ckpti-2 is the oldest checkpoint (in this example).

Assume a filesystem operation on checkpoint ckpti-2, and block n is accessed. The mapping function first checks the mapping for ckpti-2 and given it is empty, it moves forward and checks the mapping for ckpti-1. It finds m and will use block m instead of block n.

When accessing block n from ckpti, because there is no mapping, the mapping function moves forward and will use the mapping for ckpti+1, which is block p. Note that when searching for a mapping entry, the system will always move forward from current checkpoint toward more recently created checkpoints. The mapping entries of checkpoints older than the current checkpoint are never used.

Now let's see how the mappings are created. While checkpointing is active for a volume, all of the blocks of LFS are shared by checkpoint of its corresponding CFS until they are changed. As show in Figure 6-3,while block n is not modified, all the checkpoints of the filesystem use the block n itself with no mapping. If a block in the live file system is modified, then sfs2cp_notice_update( ) is called. This function first checks to see if there is an existing mapping for this block. If there is a mapping for the block, it will do nothing. If no mappings can be found and the change is not allocation, then it duplicates the block and puts the address of the new block into the mapping for the most recently created checkpoint. If the change is for block allocation, the system does not duplicate the block; it just puts a special value (SFS2CP_ALLO_MARKER) into the mapping. This is because if the block has just been allocated, there can't be any object on the checkpoints using this block (and no need to duplicate this block).

FIGURE 6-3Mappings for Block n Before Modification

Chapter 6 Checkpoints/Snapshots 6-5

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Sun Microsystems 5310 NAS manual 3Mappings for Block n Before Modification
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5310 NAS specifications

Sun Microsystems, known for its innovative computing solutions, launched the Sun 5310 Network Attached Storage (NAS) system, which marked a significant advancement in the realm of storage solutions in the early 2000s. The 5310 NAS was designed to provide high-performance, reliable, and scalable storage tailored for enterprise environments.

One of the standout features of the Sun 5310 NAS is its file-serving capabilities, which support multiple protocols, notably NFS (Network File System) and CIFS (Common Internet File System). This dual-protocol support allowed organizations to seamlessly integrate the NAS into diverse IT ecosystems, facilitating interoperability between UNIX, Linux, and Windows systems. The enhanced file-sharing capabilities made it an ideal solution for businesses with mixed operating environments.

The Sun 5310 NAS incorporates cutting-edge technologies to ensure high availability and data integrity. The system utilized a RAID (Redundant Array of Independent Disks) technology, providing various RAID levels to protect against data loss while optimizing performance. Additionally, the device featured hot-swappable drives, enabling maintenance and upgrades with minimal downtime, a crucial factor for business continuity.

Equipped with advanced management software, the Sun 5310 NAS offered users an intuitive interface for monitoring storage health and performance. This software included comprehensive reporting functionalities that allowed IT administrators to oversee usage patterns and capacity planning efficiently.

Scalability was another defining characteristic of the Sun 5310 NAS. The system could easily expand with additional storage modules, accommodating the growing needs of an organization without the necessity for complete system overhauls. This flexibility ensured that businesses could adapt their storage solutions to meet evolving data storage needs without incurring significant costs or disruptions.

In terms of performance, the Sun 5310 NAS featured high I/O throughput achieved through its robust hardware architecture and optimized file serving capabilities. This performance baseline was crucial for organizations that relied on heavy data workloads and required rapid access to information.

In summary, the Sun 5310 NAS from Sun Microsystems embodied a forward-thinking approach to network storage, blending reliability, scalability, and multi-protocol support. Its user-friendly management software, combined with the robustness of RAID technology and hot-swappable drives, made it a preferred choice for enterprises looking to streamline their storage infrastructure while safeguarding critical data.
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