Another example is when a hard-link is created in a directory named dst to a file residing in a directory called src. First, a new directory is inserted in dst. However, since volume is checkpointed, a copy of corresponding disk block is made first, and then the disk block is modified. When accessing the checkpoint version (and thus accessing the copied block), the old directory content (without the new entry) is seen. Next, the target inode is modified so the link count reflects the new directory entry (pointing to it by incrementing it). This will cause the corresponding disk block to inode data be modified and the copy containing old content will be assigned to checkpoint. Again, for someone accessing the checkpoints, the inode seems to be unchanged and everything remains perfectly consistent both in checkpoint and live file systems.

6.1.2.4Checkpoint Deletion

When a checkpoint is to be deleted, a flag is set in the entry for that checkpoint in the checkpoint control page. Later the cleaner thread for checkpoint filesystem catches the flag and scans the entire mapping for each block in filesystem and if there is a mapping entry for the checkpoint and if the previous checkpoint has no mapping for the block, then the entry is moved to the entry for the previous checkpoint. Otherwise if the mapping is not SFS2CP_ALLO_MARKER, the block is freed. Then all of the entries for checkpoint after the one that is to be deleted are moved to the left.

For example in Figure 6-2,when deleting ckpti-1, m is moved to the entry for ckpti- 2 and all of the entries after ckpti-1 are moved to the left (this operation is done logically in the checkpoint stack, so the actual entries are not moved, only block ownership will be delegated). So ckpti replaces ckpti-1. After changing the mappings, checkpoint stack is also updated similar to what has been done for checkpoint mapping entries. So after deleting ckpti-1, the mapping entries for block n will be as in Figure 6-6.

Chapter 6 Checkpoints/Snapshots 6-9

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Sun Microsystems 5310 NAS manual Checkpoint Deletion
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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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