Data Deduplication

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Bufferpuff Log Entry: Sector 7G. It is a common misconception among the uninitiated that Git is merely a scribe's tool for version control. Here in Bufferpuff, we know the truth: at its core, down in the metal, Git is a content-addressable filesystem. It is a storage engine forged for maximum efficiency.

The Law of Singular Existence (Blobs) {#blob-deduplication}

In the physical realm, if you forge ten identical iron daggers, you need the metal for ten daggers. But in the vaults of Git, we operate under different laws.

If I have 10 files that are byte-for-byte identical (say, containing just the letter "A"), do they occupy ten distinct spaces in our storage array? Negative.

When we cast the git add incantation, the system performs a transmutation: 1. It reads the raw essence (content). 2. It calculates a Hash (SHA-1)—a unique magical signature based exclusively on this essence. 3. It compresses the data into an object we call a Blob (Binary Large Object), or as we prefer, an Iron Ingot.

  • The Mechanism: The system is blind to the filename. It only sees the alloy composition (the sequence of bytes).
  • The Result: If file1.txt and file10.txt hold the same content, they generate the same Hash.
  • The Storage: Since the Hash is the primary key in our .git/objects database, the system detects the pre-existence of the Ingot. Therefore, only a single physical Blob is stored on the disk platter.

The Legend of the Gigabyte (Storage Efficiency) {#storage-efficiency}

Consider the implications for our server racks. If a novice copies a 1GB artifact ten times within a project and commits it, does our disk usage spike by 10GB?

No. We only store 1GB of actual data.

Git acts as a deduplication engine. * Internal Logic: Unlike archaic systems (like SVN) that track differences, Git tracks snapshots. But if the snapshot contains an object with a known Hash, it simply reuses the pointer to the existing Ingot. * Hardware Impact: We save disk I/O and precious blocks of storage. It is the ultimate compression of reality.

The Rack Manifest (Tree Objects) {#tree-objects}

If the Blob is the raw material, the Tree object is the Inventory Manifest. It is the equivalent of a directory structure in our server OS.

While the Ingot holds the "what", the Tree holds the "where". If I have a.txt and b.txt with identical content, the Tree object records this (simplified binary representation):

100644 blob X   a.txt
100644 blob X   b.txt
  • The Pointer System: The Tree declares: "The label a.txt points to Storage Bin (Hash) X" and "The label b.txt also points to Storage Bin (Hash) X".

The Ingot is agnostic to its label. The Tree provides the context—permissions and names. When we duplicate files, the Tree grows slightly (to add a new line to the manifest), but the heavy Iron Ingots in the vault do not multiply.

Technical Schematics: Tree vs. Blob {#tree-vs-blob}

To clarify the architecture for the junior sysadmins:

  • Blob (Ingot): The minimum unit of storage. Compressed raw bytes. No name. No permissions.
  • Tree (Manifest): A file containing a list of references. Each line contains:
    • Mode: Permissions (executable or not).
    • Type: Blob or another Tree (subdirectory).
    • Hash: The address of the object.
    • Name: The filename.

A Commit points to a root Tree. This Tree points to Blobs or sub-Trees, forming a Directed Acyclic Graph—a structure as sturdy as a reinforced chassis.

Anomaly: The Void Ingot (Null Content) {#null-content}

Can a file exist if it contains nothing? Can we store a vacuum?

In Bufferpuff, we do not deal in philosophy, but in bytes. Git does not see "null" as an absence, but as a sequence of 0 bytes.

  • The Calculation: When we git add an empty file, Git creates a header (size 0) and hashes it.
  • The Constant: The resulting hash for an empty file is a universal constant across all Git repositories: e69de29bb2d1d6434b8b29ae775ad8c2e48c5391.

Therefore, a physical object exists for the void. It is a Blob containing the compressed representation of nothingness.

Extreme Efficiency

If I create 50 empty placeholder files (.gitkeep, touch1, touch2), how many objects enter the vault?

One. The single Blob with hash e69d....

The Tree will have 50 entries, all pointing to that same identifier. We represent 50 logical files with one physical speck of data. This is the efficiency that keeps the castle standing.

The Iron Vault is sealed once more.

When disks fill, when repositories grow heavy, when others fear copies and chaos,
Bufferpuffs trust the vault.

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