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Ensuring Data Redundancy in Plan 9: Using `venti/mirrorarenas` Introduction Plan 9 from Bell Labs uses innovative methods for distributed computing. Venti, a key component, offers content-addressable storage. Ensuring redundancy for Venti archives is vital. This guide explains how to set up `venti/mirrorarenas` to mirror arenas automatically and why it is preferred over `fs(3)` mirror. Setting Up `venti/mirrorarenas` for Automatic Mirroring 1. Configure the Second Venti Server: Set up a second Venti server as described in the `venti(8)` manual page. If both servers run on the same machine, ensure they use different port numbers. 2. Create a Configuration File: Create a configuration file (`/sys/lib/venti/mirrorconf`) specifying the source and destination arenas: index main isect /dev/sdN0/index arenas /dev/sdN0/arenas /dev/sdM0/arenas-mirror 3. Format the Index and Arenas: Format the primary and mirrored arenas: venti/fmtisect isect0 /dev/sdN0/index venti/fmtarenas -a 512M /dev/sdN0/arenas venti/fmtarenas -a 512M /dev/sdM0/arenas-mirror 4. Start the Venti Server: Initialize and start the Venti server with the configuration file: venti -c /sys/lib/venti/mirrorconf 5. Run `venti/mirrorarenas`: Use `venti/mirrorarenas` to start the mirroring process: venti/mirrorarenas -c /sys/lib/venti/mirrorconf Advantages of `venti/mirrorarenas` - Speed: `venti/mirrorarenas` is fast and includes checks to ensure the arena geometries match. - Fault Tolerance: Ensures data availability by mirroring data in real-time across multiple storage devices. - Automation: Once set up, it continuously mirrors data with minimal administrative intervention. Alternative Methods for Mirroring Venti Servers 1. Using `venti-copy`: - Purpose: Copies blocks from one Venti server to another. - Usage: cat scores.txt | while read score ; do venti-copy $venti1 $venti2 $score ; done 2. Using `venti-rdarena` and `venti-wrarena`:** - Purpose: Reads and writes arenas one by one. - Usage: venti-rdarena /dev/sdN0/arenas | venti-wrarena /dev/sdM0/arenas-mirror 3. Manual Copy Using `dd`: - Purpose: Manually copies arenas using `dd`. - Usage: for i in $(seq $start $end); do echo "Copying arena $i..." skip=$(( 97 + $i * 65536 )) dd if="$orig" bs=8192 skip=$skip count=65536 seek=$skip of="$dest" done Building Arenas Post-Mirroring After copying or mirroring arenas, the destination server must recognize the new data structure: venti-buildarenas -c /sys/lib/venti/mirrorconf Comparison with `fs(3)` Mirroring - Scope: - `venti/mirrorarenas` is specialized for Venti archives, handling content-addressable storage efficiently. - `fs(3)` mirror is a general-purpose tool for mirroring entire filesystems. - Configuration Complexity: - `venti/mirrorarenas` requires specific Venti configuration, ensuring precise data handling. - `fs(3)` mirror is simpler but not optimized for Venti’s unique storage model. - Performance: - `venti/mirrorarenas` is optimized for Venti’s needs, providing faster and more reliable redundancy. - `fs(3)` mirror might introduce more overhead due to its broader functionality. Conclusion Using `venti/mirrorarenas` for Venti-specific redundancy offers a tailored, efficient solution. It automates the mirroring process, ensuring continuous data protection. Compared to `fs(3)` mirror, it provides a more specialized approach, optimized for Venti’s content-addressable storage. This choice ensures data resilience in Plan 9 systems, safeguarding against hardware failures. For broader filesystem redundancy, `fs(3)` mirror remains a versatile option, but for Venti archives, `venti/mirrorarenas` is the preferred tool. Reference For more details, see [How to mirror one Venti to another](https://www.cespedes.org/blog/tag=69). Copyright 2024 by Kalona Ayeliski. All rights reserved. ------------------------------------------ 9fans: 9fans Permalink: https://9fans.topicbox.com/groups/9fans/Tca0eb0fbb2404e31-M01f451723e39ea2e8491cf32 Delivery options: https://9fans.topicbox.com/groups/9fans/subscription
