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Dell - Hard Drive Capacity Difference Between Drives

The capacity difference between the two drives is caused by differing logical block/sector formatting or OEM vendor provisioning (HPA / Max LBA limits).

Even within the same Western Digital / Ultrastar DC HC520 12TB family, SAS drives are deployed with different low-level format structures:

1. Different Sector Formats (512e vs. 4Kn vs. Enterprise 520/528 Bytes)

  • Standard 12TB: Typically reports around 11,175.5 GB ($11.17\text{ TiB}$) when formatted with standard 512-byte emulation (512e) or 4096-byte native (4Kn) sectors.

  • Enterprise SAN/EMC Formats: Drives pulled from proprietary SAN enclosures (EMC, NetApp, Huawei) often use 520-byte or 528-byte sectors (or Type 1/2 Data Integrity Field protection). When translated or truncated by a Dell PERC/HBA, the usable LBA count drops, showing up around 10,948.5 GB.

2. OEM Firmware & Provisioning (HPA / Max LBA)

If one drive came from an OEM vendor (e.g., NetApp, EMC, Cisco, HPE) and the other is a generic Dell/retail drive, the OEM firmware may restrict the drive's total accessible Logical Block Addressing (LBA) count via Host Protected Area (HPA) or factory provisioning.

How to Fix / Match Them

To get disk 0:1:3 to match 0:1:4 at full capacity:

  1. Check the Sector Size:

    Boot into a Linux live environment (or pass the drive through via HBA/IT-mode) and run:

    Bash 
    smartctl -i /dev/sdX
# or
sg_scan -i

    Check the Logical block size and Formatted with type 1/2/3 protection values.

  2. Low-Level Format to Standard 512e / 4Kn:

    Using the sg3_utils package in Linux, reformat the drive to standard 512-byte or 4096-byte sectors:

    Bash 
    # Reformat to standard 512-byte sectors:
sg_format --format --size=512 /dev/sdX

    (Note: This is a low-level format that will erase all data on that specific disk and takes several hours for a 12TB drive.)

  3. Reset Max LBA (if sector size is already 512):

    If the drive was already 512 bytes, reset any HPA/LBA clamp:

    Bash 
    hdparm -N /dev/sdX
# To restore full native capacity:
hdparm -N p[max_lba_value] /dev/sdX

Once reformatted, the Dell PERC controller will detect 0:1:3 at the full 11175.5 GB size.

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