A RAID rebuild is the data reconstruction process that occurs when a hard disk drive needs to be replaced. When a disk fails unexpectedly, a RAID array copies data to a spare drive while the failed one is replaced. Data is then reassembled on the new drive using RAID algorithms and parity data.
RAID ("Redundant Array of Inexpensive Disks" or "Redundant Array of Independent Disks") is a data storage virtualization technology that combines multiple physical disk drive components into one or more logical units for the purposes of data redundancy, performance improvement, or both.
Yes, that's the purpose of RAID-1. When a drive in RAID-1 fails the raid enters "rebuild mode". When the failed drive is replaced it will automatically start cloning the data from the intact disk. "how" you rebuild it is entirely dependent on the raid controller.
The SATA standard supports hot-swapping so both disks and the NAS support it: "Unlike PATA, both SATA and eSATA support hot swapping by design."
Go to “Storage Manager” > “Storage Space“. Select the storage pool that will be expanded, then click “Manage“. The “Storage Pool Management” window will appear, select the RAID group that will be expanded and click “Replace Disks One by One” in the “Manage” menu.
Right-click the available hard drive on which to rebuild the RAID 1 volume and click Rebuild to this Disk. The computer can be used normally while it is rebuilding the RAID 1 volume.
How to Replace a Failed Hard Drive in Your Synology NAS
- Step One: Identify the Failed Drive. When a hard drive fails, Synology lets you know about it by loudly beeping at you.
- Step Two: Remove and Replace. After determining which hard drive went kaput, you can remove it from the NAS enclosure.
- Step Three: Test the New Hard Drive.
- Step Four: Repair the Volume.
To replace drives:
- Open Storage Manager.
- Go to Storage Pool to see which existing drive is the smallest.
- Turn off your Synology NAS.
- Remove the smallest of the member drives and install a new, larger drive.
- Turn on your Synology NAS.
- Open Storage Manager again.
- Go to HDD/SSD to make sure the new disk is recognized.
Hot Spare: On models that support the feature, a hot spare is an HDD that occupies a spare drive slot. It is initialized and registered in Storage Manager as a Hot Spare. If another drive goes into a degraded state, the system will bring the hot spare on line to replace the faulty drive.
With Unified Controller, you may combine multiple drives into a single storage unit called a storage pool. Volumes can be created on top of storage pools. Volumes may be expanded if a storage pool has allocatable space. Different RAID types offer varying levels of data protection.
Data Scrubbing is a data maintenance feature that inspects storage pools. File system scrubbing: This function will check the volumes in Btrfs file system. If any data inconsistent with the checksum is detected, the system will try to use a backup to repair the data and the file path will be recorded in Log Center.
Log into the web interface and go to Main Menu > Storage Manager > HDD Management. You can also schedule a more in-depth SMART test using the Test Scheduler Option on this screen. As Daxlerod has stated you should use the SMART tools, however you also need to perform what is called data scrubbing.
Synology Hybrid RAID (SHR) is an automated RAID management system from Synology, designed to make storage volume deployment quick and easy.
Go to Synology High Availability > Storage > Volume and select the degraded storage space. Click the Repair button.
How to recover RAID
- Download, install, and launch ReclaiMe Free RAID Recovery software.
- If needed, open or create disk image files of the member disks using the Disks button.
- Decide on the type of your array.
- Wait until the software completes detecting the parameters.
- At the step all the parameters have been already restored.
RAID Disk Failure Calculator from Memset
| Disk Size (GB) | Rebuild Time | raid6 with 1 hotspare |
|---|
| DLO/y |
|---|
| 250 | 6 hours, 56 minutes | 1 in 802.0 |
| 500 | 13 hours, 53 minutes | 1 in 646.6 |
| 1000 | 1 day, 3 hours | 1 in 402.2 |
Replacing a Failed Mirror Disk in a Software RAID Array (mdadm)
- Mark the disk as failed. # mdadm --manage /dev/md0 --fail /dev/sdb1.
- Remove the disk by mdadm. # mdadm --manage /dev/md0 --remove /dev/sdb1.
- Replace the disk. Replace the faulty disk with new one.
- Copy the partition table to the new disk.
- Create mirror.
- Verify.
"Volumes with Rebuild status will be rebuilt within the operating system" means exactly that, Rapid Storage relies on a driver within the OS to perform it's work. It is incapable of doing any actual RAID'ing by itself.
It depends on your RAID solution. Many RAID solutions format a disk when constructing a RAID or adding a new disk. Desktop versions of Windows Windows have a built-in software RAID capability which will attempt to preserve your data during conversion.
Bring a foreign disk back to an online state
- Right-click on the disk and select Import Dynamic Disk Group. A dialog box comes up that displays the name of the dynamic disk group.
- Indicate the name for the dynamic disk group as follows:
- If you import a dynamic disk group from a different system, then click the check box to clear the host ID of the other system.
When a single disk in a RAID 5 disk array fails, the disk array status changes to Degraded. The disk array remains functional because the data on the failed disk can be rebuilt using parity and data on the remaining disks. If a hot-spare disk is available, the controller can rebuild the data on the disk automatically.
To replace a failing RAID 6 drive in mdadm :
- Identify the problem. More Linux resources. Advanced Linux Commands Cheat Sheet for Developers.
- Get details from the RAID array.
- Remove the failing disk from the RAID array. Shut down the machine and replace the disk. Partition the new disk.
- Verify recovery.
