Storage Fact Sheet

Storage ClassHigh AssuranceBasic ArchiveDeep Archive
ProviderAWS S3 & GlacierAWS GlacierAWS Glacier Deep Archive
TypeHot & ColdColdFrozen
Replications6 copies (3 hot, 3 cold)3 copies (single region)3 copies (single region)
GeographyNorthern Virginia (hot) & Oregon (cold)Northern Virginia, Ohio, or OregonNorthern Virginia, Ohio, or Oregon
Fixity Interval90 daysN/AN/A
Cost/Year$0.41016/GB ($420/TB)$0.05859/GB ($60/TB)$0.01953/GB ($20/TB)
Note: APTrust measures preservation storage using the binary method (1 TB = 1024 GB) on the last day of each month.

All storage classes include:

  • Object management through Registry, APTrust’s preservation repository.
  • Event history through PREMIS metadata.
  • Fixity checks upon ingest and restoration.
  • Creation of MD5, SHA1, SHA256, and SHA512 checksum digests.
  • DART, a packaging and transfer tool for desktops and servers.

High Assurance

The High Assurance storage class makes sense for objects that are high-value and/or will be regularly replaced with new versions. See the Core Preservation Policy for full details on preservation activities for High Assurance.

  • High redundancy. APTrust stores six copies of each file across multiple AWS regions and availability zones.
  • Geographic diversity. These files are stored in S3 in Virginia and Glacier in Oregon.
  • Regular fixity checks. APTrust runs fixity checks on these files every 90 days.
  • Rapid restoration. Items in Standard storage can typically be restored within a few hours at no cost to the depositor.
  • No minimum retention period.

Basic Archive

The Basic Archive storage class makes sense for objects you want to preserve at minimal cost and are that are unlikely to change.

  • Reduced number of copies for reduced cost. Three copies in a single region. Glacier-only storage is significantly less expensive than S3 storage.
  • No added fixity checking. Fees for retrieving Glacier files every 90 days would be prohibitive.
  • Longer restoration time. Restoring bags from Glacier involves the extra step of temporarily moving files from Glacier to S3 before reconstructing a bag. This step usually takes several hours.
  • Encryption at rest. All Glacier files are encrypted at rest and decrypted upon retrieval. AWS manages the encryption keys as well as the encryption/decryption of data.
  • 90-day minimum retention: AWS Glacier requires that content must be stored for at least 90 days before it can be deleted.

Deep Archive

The Deep Archive storage class makes sense for objects you want to preserve at minimal cost but never expect to retrieve. Deep Archive has a 180-day minimum retention period imposed by AWS. The primary difference from Basic Archive, apart from a longer minimum retention, is the longest restoration time which can take days or weeks.

Last updated in May 2024.