Cloud Storage Study Notes

Cloud Storage is Google Cloud's managed object storage service for unstructured data such as images, backups, logs, and media files. Objects are stored in globally unique buckets and accessed over HTTP using a flat namespace, not a real file system hierarchy. It offers very high durability and availability by redundantly storing data across zones or regions depending on the location type you choose.

Key facts

• Buckets have a globally unique name, a location, a default storage class, and a location type of region, dual-region, or multi-region that determines availability and replication behavior.
• The four storage classes are Standard for frequently accessed data, Nearline for access roughly monthly, Coldline for quarterly access, and Archive for access less than once a year, each with different minimum storage durations.
• Minimum storage durations are 30 days for Nearline, 90 days for Coldline, and 365 days for Archive, and early deletion charges apply if an object is deleted before that period ends.
• Object Lifecycle Management rules can automatically transition objects to colder classes, set time to live for deletion, or abort incomplete multipart uploads based on age, storage class, or other conditions.
• Object Versioning, when enabled, keeps noncurrent versions of overwritten or deleted objects, which protects against accidental deletion but increases storage used until lifecycle rules clean old versions.
• Access control is governed by IAM and bucket-level policies, with uniform bucket-level access recommended because it uses only IAM and disables legacy access control lists for simpler auditing.
• Signed URLs grant time-limited access to an object without requiring the requester to have a Google account, and they are commonly tested as the answer for temporary external sharing.
• Customer-managed encryption keys via Cloud KMS and customer-supplied encryption keys are options beyond Google-managed encryption, which encrypts data at rest by default for every object.
• Storage Transfer Service and gsutil are used to move data into Cloud Storage, while Pub/Sub notifications and Object Change Notifications can trigger workflows when objects are created or updated.

What the exam expects you to know

• Choose the correct storage class from access frequency in the scenario, for example Archive for compliance backups accessed yearly and Standard for website assets served daily.
• Recognize lifecycle rules as the automated way to control costs, rather than manually moving objects or writing scripts to delete old data.
• Know that uniform bucket-level access is preferred and that enabling it permanently disables ACLs after a transition period, which affects legacy integrations.
• Identify signed URLs for temporary, unauthenticated access and VPC Service Controls or retention policies for preventing deletion in governance scenarios.
• Understand regional versus dual-region and multi-region buckets for availability, disaster recovery, and serving users close to where they are located.
• Remember that Cloud Storage is object storage, not block or file storage, so it cannot be mounted as a boot disk or used directly for a shared POSIX file system.

Cloud Storage vs Filestore: when to use which

Use Cloud Storage when you need to store and serve unstructured objects at massive scale over HTTP, such as images, videos, backups, and data lake files, with lifecycle and versioning controls. Use Filestore when applications require a traditional file system with NFS, directory hierarchies, file locking, and low-latency POSIX semantics, for example legacy applications lifted to the cloud unchanged. The exam decision is usually protocol and access pattern: object API and global scale point to Cloud Storage, while mountable shares and OS-level file operations point to Filestore. Cost also differs, as colder Cloud Storage classes are far cheaper for rarely accessed data. See also the Filestore notes.

Useful gcloud commands

gsutil mb -l us-central1 gs://my-bucket-name
gsutil cp local-file.txt gs://my-bucket-name/path/
gsutil lifecycle set lifecycle.json gs://my-bucket-name
gsutil versioning set on gs://my-bucket-name

Common exam traps

• Folders in the console are simulated prefixes, not real directories, so renaming a folder actually copies and deletes every object under that prefix.
• Nearline, Coldline, and Archive have retrieval costs and minimum durations, so choosing the cheapest storage price alone can increase total cost for frequently accessed data.
• Public access is not the default and requires explicit IAM grants; making a bucket public by granting allUsers is a security risk the exam expects you to avoid.
• Cloud Storage does not support appending to an object in place; you must rewrite the object or use compose operations to combine objects.

Frequently asked questions

When should I enable Object Versioning?

Enable Object Versioning when you need protection against accidental overwrites or deletions and want to restore a previous version of an object. It is useful for important buckets where recovery matters more than extra storage cost. Pair it with lifecycle rules that delete noncurrent versions after a set number of days to control costs.

What is uniform bucket-level access?

Uniform bucket-level access means permissions for a bucket and its objects are controlled only through IAM, with access control lists disabled. This simplifies management, provides consistent auditing, and is the recommended setting for new buckets. Once enforced for a long period it becomes permanent, so check for legacy ACL dependencies before enabling it.

How do lifecycle rules save money?

Lifecycle rules automatically move aging objects to cheaper storage classes or delete them when they are no longer needed, based on conditions you define such as age or current class. For example, logs can move to Nearline after thirty days and to Archive after a year. This automation avoids manual cleanup and steadily reduces storage costs.

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