How to replace failing Disk 1?

Any 500GB drive or larger that is on the Hardware Compatibility List (HCL) can be used. The limitation is that the drive must be equal in size or larger than the current drive. If you purchased the NV+ with the two drives, considering the time frame in which you made your purchase, they are probably Enterprise class drives with a 5 year warranty and Rotational Vibration Safeguard which is critical in arrays of large number of drives (such as the 4200 rack mount with 12 drives) but is less important in small arrays such as yours. Some feel the extra money is worthwhile, while others point out that the higher priced drives will fail as well. (All drives fail, it is a question of when).

You can look in Frontview -> Status -> Health to see the list of drives, click on the Smart+ button to see the detailed list of statistics as well as the make and model of the drive and serial number. While I like, if possible to have a matched set of drives, it is unnecessary and I now have two NAS units with two different sizes and brand of drives. Another member pointed out that 500GB drives that are on the NV+ HCL are getting hard to find and I pointed out to him that it may be a time to start the upgrade to 1TB or even 2TB drives. It is unfortunate that the current prices are elevated because of the flooding in Thailand.

If you replace the 500GB drive with a larger drive only 500GB of the capacity will be used by the array until all drives are equal to or larger than the drive you install. The procedure is to hot pull the failing drive, wait for the NV+ to recognize that the drive has been pulled (on the front panel, you will be first told the drive has failed, then it will be reported as dead and finally as missing) and then hot add the new drive. You can shut it down, remove the failed drive, install the new drive and reboot. This will, however, require the drive to have no data or partitions on it.

Please make sure that you have a current and complete backup of all your data (of course you maintain one anyway) as the resync process will put a lot of strain on the other drive with constant activity for 5-8 hours. If this drive fails during the resync process, the array will be gone (with the data).