Applicable Products
Scenario
A disk failure can make a volume degraded or inaccessible. What happens next depends on the RAID configuration. In particular, Single-disk and RAID 0 configurations provide no protection against disk failure. Consider the risk and maintain a separate backup before using either configuration.
The case that prompted this FAQ involved a two-disk RAID 0 group on a TS-251D. After one disk failed, the volume became unavailable and the installed apps disappeared. Replacing the failed disk alone could not restore the RAID 0 volume or its files.
Disk Failure Behavior by Configuration
| Configuration |
Protection against disk failure |
What may happen if a disk fails |
| Single |
None |
The storage on that disk becomes unavailable. There is no redundant copy in the configuration to recover it. |
| RAID 0 |
None |
Data is striped across all member disks. Failure of any member can make the entire RAID group and its volume inaccessible. Replacing the failed disk does not recreate the missing data. |
| JBOD |
None |
Disks are combined without redundancy. Data on the failed disk may be lost, and the combined volume or data on other disks may also become inaccessible, depending on the layout and failure. |
| RAID 1 |
One disk |
The group may continue operating in a degraded state using the remaining mirror. A second disk failure before recovery can make data inaccessible. |
| RAID 5 |
One disk |
The group may continue operating in a degraded state. A further disk failure before the group is restored can make data inaccessible. |
| RAID 6 |
Two disks |
The group may continue operating with one or two failed disks. Failure beyond its tolerance can make data inaccessible. |
| RAID 10 |
One disk per mirrored pair |
The group can tolerate a disk failure in a mirror pair, but not the loss of both disks in the same pair. |
| RAID 50 |
One disk per RAID 5 subgroup |
The group can tolerate one failed disk in each subgroup. More than one failure in a subgroup can make the group inaccessible. |
| RAID 60 |
Two disks per RAID 6 subgroup |
The group can tolerate up to two failed disks in each subgroup. More failures in a subgroup can make the group inaccessible. |
These are general failure tolerances, not guarantees that data will remain accessible or that a rebuild will succeed. Actual symptoms and recovery options depend on the NAS model, firmware, storage layout, disk condition, and whether other errors occur.
What to Do
If data is still accessible
- Back up important data to a separate destination as soon as possible. Do not treat RAID redundancy as a backup.
- Verify that the backup completed and that important files can be opened or restored.
- Check Storage & Snapshots for the affected disk and RAID status. Record the NAS model, firmware, disk bay, status messages, and relevant logs.
- For a redundant RAID group, follow the NAS interface or QNAP Support guidance to replace the confirmed failed disk and monitor the rebuild. Do not remove another disk while the group is degraded.
If the volume is inaccessible or the configuration has no redundancy
- Stop making configuration changes. Do not initialize, format, recreate, or repeatedly rebuild the storage group, and do not replace additional disks.
- Keep the original disks and their bay order unchanged. If the data is important and no usable backup exists, contact QNAP Support or a qualified data recovery provider before attempting recovery. Recovery is not guaranteed.
- If a verified backup is available, replace the failed disk as appropriate, recreate the storage configuration if needed, and restore the data from that backup.
In the TS-251D case, the two-disk RAID 0 volume became Not active after one disk failed. Installing a replacement disk by itself could not restore the volume or its files. The advised recovery path was to recreate the storage configuration and restore from backup; without a backup, avoid further changes and seek professional recovery assistance if the data is important.
Prevention
- Choose a RAID type with suitable disk-failure tolerance for the importance of the data. RAID 1, for example, can tolerate one disk failure in a two-disk mirror.
- Keep regular, versioned backups on a separate system or destination, and test that files can be restored.
- Consider backup coverage for the NAS configuration and applications as well as shared-folder data.
- For RAID 0, Single, or JBOD, plan for the possibility that a disk failure will interrupt access to data; these configurations do not provide disk-failure protection.
Related Links
适用产品
场景
磁盘故障可能导致卷降级或无法访问。接下来的情况取决于 RAID 配置。特别是，单盘和 RAID 0 配置不提供磁盘故障保护。在使用这两种配置之前，请考虑风险并保持单独备份。
引发此常见问题的案例涉及 TS-251D 上的一个双盘 RAID 0 组。在一个磁盘故障后，卷变得不可用，已安装的应用程序消失。仅更换故障磁盘无法恢复 RAID 0 卷或其文件。
按配置的磁盘故障行为
| 配置 |
磁盘故障保护 |
如果磁盘故障可能发生的情况 |
| 单盘 |
无 |
该磁盘上的存储变得不可用。配置中没有冗余副本来恢复它。 |
| RAID 0 |
无 |
数据在所有成员磁盘上分条。任何成员的故障都可能导致整个 RAID 组及其卷无法访问。更换故障磁盘不会重建丢失的数据。 |
| JBOD |
无 |
磁盘组合在一起没有冗余。故障磁盘上的数据可能丢失，组合卷或其他磁盘上的数据也可能无法访问，具体取决于布局和故障情况。 |
| RAID 1 |
一块磁盘 |
该组可能在降级状态下继续运行，使用剩余的镜像。在恢复之前的第二次磁盘故障可能导致数据无法访问。 |
| RAID 5 |
一块磁盘 |
该组可能在降级状态下继续运行。在组恢复之前的进一步磁盘故障可能导致数据无法访问。 |
| RAID 6 |
两块磁盘 |
该组可能在一块或两块磁盘故障的情况下继续运行。超出其容忍度的故障可能导致数据无法访问。 |
| RAID 10 |
每个镜像对一块磁盘 |
该组可以容忍镜像对中的一个磁盘故障，但不能同时丢失同一对中的两个磁盘。 |
| RAID 50 |
每个 RAID 5 子组一个磁盘 |
该组可以容忍每个子组中一个磁盘故障。子组中超过一个故障可能导致组不可访问。 |
| RAID 60 |
每个 RAID 6 子组两个磁盘 |
该组可以容忍每个子组中较多两个磁盘故障。子组中更多故障可能导致组不可访问。 |
这些是一般的故障容忍度，并不保证数据仍然可访问或重建会成功。实际症状和恢复选项取决于 NAS 型号、固件、存储布局、磁盘状况以及是否发生其他错误。
怎么办
如果数据仍然可访问
- 尽快将重要数据备份到单独的目的地。不要将 RAID 冗余视为备份。
- 验证备份是否完成，并确保重要文件可以打开或恢复。
- 检查存储与快照总管以获取受影响磁盘和 RAID 状态。记录 NAS 型号、固件、磁盘槽位、状态消息和相关日志。
- 对于冗余 RAID 组，按照 NAS 界面或 QNAP 支持的指导更换确认故障的磁盘并监控重建。在组降级时不要移除其他磁盘。
如果卷无法访问或配置没有冗余
- 停止进行配置更改。不要初始化、格式化、重新创建或反复重建存储组，也不要更换额外的磁盘。
- 保持原始磁盘及其插槽顺序不变。如果数据重要且没有可用的备份，请在尝试恢复之前联系QNAP 支持或合格的数据恢复提供商。恢复无法保证。
- 如果有经过验证的备份，请根据需要更换故障磁盘，重新创建存储配置，并从该备份中恢复数据。
在 TS-251D 案例中，两磁盘 RAID 0 卷在一个磁盘故障后变为未激活。单独安装替换磁盘无法恢复卷或其文件。建议的恢复路径是重新创建存储配置并从备份中恢复；如果没有备份，避免进一步更改，并在数据重要时寻求专业恢复帮助。
预防
- 根据数据的重要性选择具有适当磁盘故障容忍度的 RAID 类型。例如，RAID 1 可以在两磁盘镜像中容忍一个磁盘故障。
- 在单独的系统或目的地上保持定期的、版本化的备份，并测试文件是否可以恢复。
- 考虑对 NAS 配置和应用程序以及共享文件夹数据的备份覆盖。
- 对于 RAID 0、单一或 JBOD，计划磁盘故障可能会中断数据访问；这些配置不提供磁盘故障保护。
相关链接
