Cloud Object Storage (COS)

Cloud Object Storage (COS) is Tencent Cloud's highly scalable, durable, and cost-effective object storage service. COS is the equivalent of AWS S3 or Alibaba Cloud OSS.

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What is Object Storage?

Object storage stores data as objects within buckets. Each object consists of:

• Key — a unique name within the bucket (e.g., images/photo.jpg)
• Data — the file content (up to 48.82 TB per object)
• Metadata — information about the object (content type, custom headers)

Object storage uses a flat namespace — key prefixes simulate a folder structure.

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Buckets

A bucket is a container for objects:

• Globally unique name — format: <BucketName-APPID> (e.g., my-bucket-1250000000)
• Region-specific — each bucket is created in a specific region
• Unlimited objects — no limit on number or total size
• Access control — private, public-read, or public-read-write

Bucket Naming Rules

• 1 to 50 characters (excluding APPID suffix)
• Lowercase letters, numbers, and hyphens
• Cannot start with a hyphen

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Storage Classes

COS offers multiple storage classes to balance cost and access patterns:

Storage Class	Use Case	Retrieval	Min Duration
Standard	Frequently accessed, hot data	Immediate	None
Standard-IA (Infrequent Access)	Accessed less than once a month	Immediate	30 days
Intelligent Tiering	Unknown or changing access patterns	Automatic	None
Archive	Rarely accessed, retrieval in minutes	1–5 minutes (expedited) to 3–5 hours	90 days
Deep Archive	Long-term compliance archival	12–24 hours	180 days

Intelligent Tiering

Intelligent Tiering automatically moves objects between access tiers based on usage:

• Frequent Access tier (accessed recently)
• Infrequent Access tier (not accessed for 30+ days)
• No retrieval fees — automatic and transparent

Lifecycle Rules

Automate data management:

Day 0:   Upload to Standard
Day 30:  Transition to Standard-IA
Day 90:  Transition to Archive
Day 365: Delete

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Durability and Availability

Storage Class	Durability	Availability
Standard	99.999999999% (eleven 9s)	99.95%
Standard-IA	99.999999999%	99.9%
Intelligent Tiering	99.999999999%	99.95%

COS achieves this durability by storing data redundantly across multiple devices and facilities within a region.

Redundancy Options