Storage Fact Sheet

Storage Class	High Assurance (Standard)	Basic Archive	Deep Archive
Provider	AWS S3 & Glacier	AWS Glacier	AWS Glacier Deep Archive
Type	Hot & Cold	Cold	Frozen
Assurance	High	Medium	Medium
Replications	2 copies (1 hot, 1 cold)	1 cold copy (single region)	1 frozen copy (single region)
Geography	Northern Virginia (hot) & Oregon (cold)	Northern Virginia, Ohio, or Oregon	Northern Virginia, Ohio, or Oregon
Fixity Interval	90 days	N/A	N/A
Restoration Time	1-6 hours	6-12 hours	12-24+ hours
Minimum Retention	None	90-days	180-days
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 (Standard)

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. (The High Assurance storage class is sometimes called “Standard”; when APTrust started, it was the only storage class available.)

High redundancy. APTrust stores two 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. One copy 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 December 2024.