Applicable Products
All NAS running QTS system
Scenario
You may wish to configure RAID on your QNAP NAS using hard drives of different capacities. RAID (Redundant Array of Independent Disks) combines multiple physical drives into a single logical unit, providing various options for data protection, usable capacity, and performance.
Example: Suppose you have 4 x 6TB and 4 x 8TB hard disks in your NAS. Your RAID configuration choices will affect how much storage space you can use, the level of fault tolerance, and overall performance. The following options explain common ways to configure RAID with mixed-capacity drives and the trade-offs involved.
Option 1: Create two separate RAID 5 arrays (by capacity group)
Configuration
- RAID 5 (4 x 6TB disks): In RAID 5, one disk's capacity is reserved for parity (error correction data). Usable capacity ≈ 18TB.
- RAID 5 (4 x 8TB disks): Usable capacity ≈ 24TB.
Benefits
- Simple and reliable.
- Maximizes the usable capacity of each disk group.
- Each RAID group can be managed or expanded independently.
- Failure in one group doesn't affect the other.
Disadvantages
- Storage pools are separate; you do not get a single large volume spanning all drives.
- Less flexible if you want to combine all drives into one volume.
Option 2: Create a single RAID 5 with mixed drives, plus a hot-spare disk
Configuration
- RAID 5 (4 x 6TB + 3 x 8TB disks): RAID groups use the smallest disk size for all included drives. Here, each drive is treated as 6TB, so total raw capacity is 42TB. RAID 5 reserves the equivalent of one disk for parity, leaving about 36TB usable.
- One 8TB disk used as a hot-spare disk: This disk is not protected by RAID.
Benefits
- Creates a larger single volume (if needed) by combining more disks in one RAID group.
Disadvantages
- All drives in RAID are limited to the smallest disk size, so extra capacity on the 8TB disks is wasted.
- The standalone 8TB disk lacks RAID protection, increasing risk of data loss for data stored there.
- Lower storage efficiency and data protection than Option 1.
Option 3: Create a single RAID 6 with all drives
Configuration
- RAID 6 (4 x 6TB + 4 x 8TB disks): RAID 6 uses the capacity of the smallest disk and reserves two disks' worth of space for double parity. Here, all eight drives are treated as 6TB drives, so (6TB x 8) - (2 x 6TB) = 36TB usable.
Benefits
- Tolerates failure of any two drives for higher data protection.
- You can combine all drives into a single storage pool.
Disadvantages
- Extra capacity on 8TB disks is not used (wasted).
- Usable space is lower than with two separate RAID 5 arrays.
- RAID 6 has slightly lower write performance than RAID 5.
Recommendation
For most users, Option 1: Creating separate RAID 5 arrays for each disk size offers the highest usable capacity (in this example: 18TB + 24TB = 42TB), simple management, and ensures that a problem in one group does not affect the other. It also makes full use of the extra capacity on larger disks.
If the highest level of data protection is your main concern and you are willing to sacrifice some storage space, consider Option 3 (RAID 6), which can withstand any two drive failures. Just note that some of the space on your larger disks will not be usable.
Important: Always back up your important data before setting up or changing RAID arrays. Initialization will erase all data on the disks.
适用产品
所有运行 QTS 系统的 NAS
场景
您可能希望在 QNAP NAS 上使用不同容量的硬盘配置 RAID。RAID（独立磁盘冗余阵列）将多个物理驱动器组合成一个逻辑单元，提供多种数据保护、可用容量和性能选项。
示例：假设您的 NAS 中有 4 个 6TB 和 4 个 8TB 的硬盘。您的 RAID 配置选择将影响您可以使用多少存储空间、容错级别和整体性能。以下选项解释了使用混合容量驱动器配置 RAID 的常见方法及其权衡。
选项 1：创建两个独立的 RAID 5 阵列（按容量分组）
配置
- RAID 5（4 个 6TB 磁盘）：在 RAID 5 中，一个磁盘的容量用于校验（错误校正数据）。可用容量约为 18TB。
- RAID 5（4 个 8TB 磁盘）：可用容量约为 24TB。
优点
- 简单且可靠。
- 较大化每个磁盘组的可用容量。
- 每个 RAID 组可以独立管理或扩展。
- 一个组的故障不会影响另一个组。
缺点
- 存储池是分开的；您无法获得一个跨越所有驱动器的大容量卷。
- 如果您想将所有驱动器合并为一个卷，灵活性较低。
选项 2：创建一个混合驱动器的 RAID 5，并加上一个热备盘
配置
- RAID 5（4 个 6TB + 3 个 8TB 磁盘）：RAID 组使用所有包含驱动器的较小磁盘大小。在此，每个驱动器被视为 6TB，因此总原始容量为 42TB。RAID 5 保留相当于一个磁盘的容量用于校验，剩下约 36TB 可用。
- 一个 8TB 磁盘用作热备盘： 此磁盘未受 RAID 保护。
优点
- 通过将更多磁盘组合到一个 RAID 组中，创建一个更大的单一卷（如果需要）。
缺点
- RAID 中的所有驱动器都受限于较小的磁盘大小，因此 8TB 磁盘上的额外容量被浪费。
- 独立的 8TB 磁盘缺乏 RAID 保护，增加了存储在那里的数据丢失风险。
- 比选项 1 的存储效率和数据保护更低。
选项 3：使用所有驱动器创建单个 RAID 6
配置
- RAID 6（4 x 6TB + 4 x 8TB 磁盘）： RAID 6 使用较小磁盘的容量，并保留两个磁盘的空间用于双重校验。在这里，所有八个驱动器都被视为 6TB 驱动器，因此 (6TB x 8) - (2 x 6TB) = 36TB 可用。
优点
- 可以容忍任意两个驱动器的故障，以提高数据保护。
- 您可以将所有驱动器合并到一个存储池中。
缺点
- 8TB 磁盘上的额外容量未被使用（浪费）。
- 可用空间低于两个独立的 RAID 5 阵列。
- RAID 6 的写入性能略低于 RAID 5。
建议
对于大多数用户，选项 1：为每种磁盘大小创建单独的 RAID 5 阵列 提供较高的可用容量（在此示例中：18TB + 24TB = 42TB），简单的管理，并确保一个组中的问题不会影响另一个组。它还充分利用了较大磁盘上的额外容量。
如果数据保护是您的主要关注点，并且您愿意牺牲一些存储空间，请考虑选项 3（RAID 6），它可以承受任意两个驱动器的故障。请注意，您较大磁盘上的一些空间将不可用。
重要提示： 在设置或更改 RAID 阵列之前，请始终备份重要数据。初始化将擦除磁盘上的所有数据。
