Some files need to be ready the moment someone asks for them. Others, such as images used in a monthly newsletter, spend most of their time sitting quietly. Azure Storage’s Cool access tier is for data accessed infrequently that does not need the quickest retrieval. It lowers storage costs compared with Hot, but raises access costs and latency. section 5.3.1 section 9.5.1
Choose the tier according to how the data is used:
- For blobs, Hot suits frequently used or immediately needed data; Cool suits infrequent access; Archive suits rarely accessed data but requires rehydration before retrieval. section 5.3.1 section 5.8
- For Azure Files, Cool is an HDD-backed file-share tier with the lowest storage costs and highest transaction costs among the listed file-share options. Frequent transactions can erase the advantage of cheaper storage. section 5.4
Monthly newsletter images
If staff images are fetched only for a monthly newsletter, keeping them in Cool can cost less than storing them in a tier priced for frequent use. Customer order files that must appear immediately are a better fit for Hot. The right choice depends on both storage charges and what happens when someone requests a file. section 5.3.1 section 5.4
Blob access needs can change over time. A lifecycle management policy can move a block blob to Cool after 30 days without modification, then to Archive after 90 days, and delete it after 365 days. These thresholds measure time since modification—not how many times the blob was read. section 9.5.1
{
"rules": [
{
"name": "TransitionHotToColdToArchive",
"enabled": true,
"type": "Lifecycle",
"definition": {
"actions": {
"baseBlob": {
"tierToCool": {
"daysAfterModificationGreaterThan": 30
},
"tierToArchive": {
"daysAfterModificationGreaterThan": 90
},
"delete": {
"daysAfterModificationGreaterThan": 365
}
}
},
"filters": {
"blobTypes": [
"blockBlob"
]
}
}
}
]
}
The JSON policy shows the three modification-age thresholds and a filter for block blobs. Its `tierToCool` action is the step that moves eligible blobs into Cool. section 9.5.1
C:/> az storage account management-policy create --account-name banningstorage --resource-group BanningRG --policy @policy.json
After saving the policy as `policy.json`, use this Azure CLI command to create the storage account’s management policy. section 9.5.1
