Sizing a Records Digitisation Pipeline Under Storage and Throughput Constraints
A district office must digitise 4.2 million paper records before a statutory deadline in 300 working days. Each scanned page is stored as a 300 DPI greyscale TIFF averaging 1.8 MB, plus a compressed PDF derivative averaging 220 KB. Two scanner workstations each sustain 900 pages per hour during a 7-hour effective shift, but OCR post-processing on a single shared server caps throughput at 11,000 pages per day. The office has 14 TB of usable storage and a rule that raw TIFFs must be retained for 5 years while PDFs are retained indefinitely. A vendor offers a 40% smaller TIFF format that the legal team has not yet approved.
1. Determine whether the current pipeline can meet the deadline, and identify the binding constraint.
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Scanning capacity. Two workstations × 900 pages/hour × 7 hours = 12,600 pages/day. Over 300 days this gives 3.78 million pages - already below the 4.2 million target, so scanning alone is short by 420,000 pages.
OCR capacity. 11,000 pages/day × 300 = 3.3 million pages, short by 900,000 pages. OCR is therefore the binding constraint, not scanning.
Required daily rate. 4.2M / 300 = 14,000 pages/day. That exceeds both the OCR cap (11,000) and the scan cap (12,600).
Implication. Adding scanners will not help because OCR is the narrower bottleneck. The office must either extend the OCR capacity (second server or batch parallelism), extend the timeline, or reduce pages needing OCR. A correct answer names OCR as binding and quantifies the gap rather than simply saying 'capacity is insufficient'.
2. Evaluate whether the 14 TB storage will suffice, and assess the vendor's 40% TIFF reduction offer.
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Raw TIFF volume. 4.2M pages × 1.8 MB = 7.56 TB. Retained for 5 years, this is a fixed 7.56 TB commitment (assuming no re-scans).
PDF volume. 4.2M × 220 KB ≈ 0.92 TB, retained indefinitely, so it grows with any future additions but is fixed for this project.
Total. 7.56 + 0.92 = 8.48 TB, leaving about 5.5 TB headroom on 14 TB. Storage is not the binding constraint.
Vendor offer. A 40% TIFF reduction saves 0.4 × 7.56 = 3.02 TB, bringing TIFFs to 4.54 TB. This is attractive but not necessary given headroom. The decision should weigh legal admissibility risk against 3 TB of savings that the office does not urgently need. A sound judgement is to decline or defer the unapproved format until legal clearance, since the constraint is OCR throughput, not disk.