How long does it take to certify a disk

Disk certification is a thorough process that writes data to every sector on the drive and reads it back three times to ensure reliability. The time required depends on the drive capacity, type, and interface speed.

Certification Time Estimates

Hard Disk Drives (HDDs) over Thunderbolt

HDDs have the longest certification times due to mechanical limitations:

• 2TB drive: ~24 hours (1 day)
• 4TB drive: ~48 hours (2 days)
• 10TB drive: ~120 hours (5 days)
• 20TB drive: ~240 hours (10 days)

General rule: Approximately 1 day per 2TB of capacity

Note: Certification time can vary significantly based on which portion of the drive is being tested. HDDs are fastest on outer tracks (beginning of the drive) and can be less than half the speed on inner tracks (end of the drive), so certification may slow down as it progresses.

SSDs over Thunderbolt 3/4

SSDs certify much faster than HDDs due to lack of mechanical components:

• 2TB SSD: ~4-8 hours
• 4TB SSD: ~8-16 hours

Thunderbolt 3/4 bandwidth limitation: ~2,800 MB/s practical throughput per enclosure

NVMe Drives (Full PCIe Bandwidth)

Accelsior PCIe card (direct PCIe connection, full bandwidth per drive):

Each NVMe drive gets dedicated PCIe lanes with no shared bandwidth:

• 2TB NVMe: ~2-4 hours
• 4TB NVMe: ~4-8 hours

Maximum throughput: Up to 7,000 MB/s per drive (PCIe 4.0 x4), limited only by Mac Pro total bandwidth of ~18 GB/s across all slots

NVMe in Thunderblade Enclosures

Thunderblade performance is limited by Thunderbolt 3 bandwidth (~2,800 MB/s total for the entire enclosure):

4-drive Thunderblade (x4):

• Each drive gets ~700 MB/s
• 2TB NVMe: ~8-12 hours
• 4TB NVMe: ~16-24 hours

8-drive Thunderblade (x8):

• Each drive gets ~350 MB/s
• 2TB NVMe: ~16-20 hours
• 4TB NVMe: ~32-40 hours

12-drive Thunderblade (x12):

• Each drive gets ~233 MB/s
• 2TB NVMe: ~24-30 hours
• 4TB NVMe: ~48-60 hours

Key limitation: More drives in a Thunderblade means longer certification times due to shared Thunderbolt bandwidth. A 12-blade configuration will certify slower than a 4-blade configuration even though the individual drives are identical.

Why Certification Takes So Long

There are no shortcuts to proper certification. The process involves:

• Three complete passes of the entire drive
• Writing random data to every sector (passes 1-2)
• Writing zeros to every sector (pass 3, returns drive to “as new” state)
• Reading back and verifying all data after each write

Why You Should Certify

Drives are typically sold with minimal or no testing by manufacturers. Running certification is the only way to identify potential defects in the drive or communication system before putting it into production use.

A properly functioning set of drives and enclosure should never fail certification. If certification fails, it indicates a problem with the drive, enclosure, cable, or connection that needs to be addressed.