You can replace a hard drive if:
If a failed hard drive is under warranty, make certain to contact LaCie support to receive a replacement disk (see Getting Help for contact information). When adding or replacing hard drives, consider using Seagate Desktop HDD that are optimized for use with your LaCie 5big Thunderbolt 2. For further information on compatible hard drives, visit LaCie support.
Since the LaCie 5big supports hot swapping hard drives, replacing a single disk usually does not require that you power down the device before following the steps below.
When replacing disks that are members of an active RAID configuration, the disk LEDs will blink red and blue indicating that the RAID is synchronizing data. You can continue to use the LaCie 5big storage but performance will be reduced until the synchronization is complete.
The components inside the chassis are NOT hot-swappable and are NOT serviceable at any location outside of LaCie-approved service centers. Removing the cover will void your product’s warranty. Additionally, removing, replacing, or changing any part in the enclosure or, performing any action that involves the components in the enclosure, will void the product’s warranty. If you are experiencing hardware errors or failure, contact LaCie support for assistance (see Getting Help for contact information).