Retention of stale data occurs when old, no longer needed records are preserved within active Snowflake tables. Without lifecycle policies or regular purging, tables accumulate outdated data.
Because Snowflake’s compute charges are tied to how much data is scanned, retaining large volumes of inactive or irrelevant data can drive up both storage and query execution costs unnecessarily.
Snowflake automatically maintains previous versions of data when tables are modified or deleted. For tables with high churn—meaning frequent INSERT, UPDATE, DELETE, or MERGE operations—this can cause a significant buildup of historical snapshot data, even if the active data size remains small.
This hidden accumulation leads to elevated storage costs, particularly when Time Travel retention periods are long and data change rates are high. Often, teams are unaware of how much snapshot data is being stored behind the scenes.
Snapshots are often created for short-term protection before changes to a VM or disk, but many remain in the environment far beyond their intended lifespan. Over time, this leads to an accumulation of snapshots that are no longer associated with any active resource or retained for operational need.Since Azure does not enforce automatic expiration or lifecycle policies for snapshots, they can persist indefinitely and continue to incur monthly storage charges. This inefficiency is especially common in development environments, migration efforts, or manual backup workflows that lack centralized cleanup.Snapshots older than 30–90 days, especially those not tied to a documented backup strategy or workload, are strong candidates for review and removal.
EFS file systems that are no longer attached to any running services — such as EC2 instances or Lambda functions — continue to incur storage charges. This often occurs after workloads are decommissioned but the file system is left behind. A quick indicator of this state is when the EFS file system has no mount targets configured. Without active usage or connection, these orphaned file systems represent pure cost with no functional value. Unlike block storage, EFS does not require an attached instance to incur billing, making it easy for unused resources to go unnoticed.
For Premium SSD and Standard SSD disks 513 GiB or larger, Azure now offers the option to enable Performance Plus — unlocking higher IOPS and MBps at no extra cost. Many environments that previously required custom performance settings continue to pay for additional throughput unnecessarily. By not enabling Performance Plus on eligible disks, organizations miss a straightforward opportunity to reduce disk spend while maintaining or improving performance. The feature is opt-in and must be explicitly enabled on each qualifying disk.
Each Azure VM size has a defined limit for total disk IOPS and throughput. When high-performance disks (e.g., Premium SSDs with high IOPS capacity) are attached to low-tier VMs, the disk’s performance capabilities may exceed what the VM can consume. This results in paying for performance that the VM cannot access. For example, attaching a large Premium SSD to a B-series VM will not provide the expected performance because the VM cannot deliver that level of throughput. Without aligning disk selection with VM limits, organizations incur unnecessary storage costs with no corresponding performance benefit.
Workloads using legacy Premium SSD managed disks may be eligible for migration to Premium SSD v2, which delivers equivalent or improved performance characteristics at a lower cost. Premium SSD v2 decouples disk size from performance metrics like IOPS and throughput, enabling more granular cost optimization. Additionally, Premium SSD disks are often overprovisioned in size—for example, a P40 disk with more IOPS and capacity than the workload requires—resulting in inflated storage costs. Rightsizing includes both transitioning to v2 and resizing to smaller SKUs (e.g., P40 → P20) based on observed utilization. Failure to address either form of overprovisioning leads to persistent waste.
Standard SSD disks can often be replaced with Premium SSD v2 disks, offering enhanced IOPS, throughput, and durability at competitive or lower pricing. For workloads that require moderate to high performance but are currently constrained by Standard SSD capabilities, migrating to Premium SSD v2 improves both performance and cost efficiency without significant operational overhead.
Disks attached to VMs that have been stopped for an extended period, particularly when showing no read or write activity, may indicate abandoned infrastructure or obsolete resources. Retaining these disks without validation leads to unnecessary monthly storage costs. Reviewing and cleaning up inactive disks helps optimize spend and maintain storage hygiene.
Tables with no read or write activity often represent deprecated applications, obsolete telemetry, or abandoned development artifacts. Retaining inactive tables increases storage costs and operational complexity. Regularly auditing and cleaning up unused tables helps maintain a streamlined, cost-effective storage environment.
