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.
適用產品
所有執行 QTS 系統的 NAS
情境
您可能希望在 QNAP NAS 上使用不同容量的硬碟配置 RAID。RAID（獨立磁碟備援陣列）將多個實體磁碟組合成一個邏輯單元，提供多種資料保護、可用容量和效能選項。
例如：假設您的 NAS 中有 4 顆 6TB 和 4 顆 8TB 的硬碟。您的 RAID 配置選擇將影響您可以使用的儲存空間空間、容錯級別和整體效能。以下選項說明了使用混合容量硬碟配置 RAID 的常見方法及其權衡。
選項 1：建立兩個獨立的 RAID 5 陣列（按容量分組）
配置
- RAID 5（4 x 6TB 硬碟）：在 RAID 5 中，一顆硬碟的容量保留作為同位（錯誤更正資料）。可用容量約為 18TB。
- RAID 5（4 x 8TB 硬碟）：可用容量約為 24TB。
優勢
- 簡單且可靠。
- 最大化每個磁碟組的可用容量。
- 每個 RAID 組可以獨立管理或擴充套件。
- 一組故障不會影響另一組。
缺點
- 儲存空間池是分開的；您無法獲得一個跨越所有磁碟的大型磁碟區。
- 如果您想將所有磁碟合併為一個磁碟區，則靈活性較低。
選項 2：建立一個混合磁碟的 RAID 5，外加一個熱備援磁碟
配置
- RAID 5（4 x 6TB + 3 x 8TB 硬碟）：RAID 組使用所有包含磁碟的最小磁碟大小。在此，每個磁碟被視為 6TB，因此總原始容量為 42TB。RAID 5 保留相當於一顆磁碟的容量作為同位，留下約 36TB 可用。
- 一顆 8TB 硬碟用作熱備援磁碟： 此磁碟未受 RAID 保護。
成果
- 透過將多個磁碟組合成一個 RAID 群組，建立更大的單一磁碟區（如有需要）。
缺點
- RAID 中的所有磁碟都受限於最小的磁碟大小，因此 8TB 磁碟的額外容量被浪費。
- 獨立的 8TB 磁碟缺乏 RAID 保護，增加了儲存在那裡的資料遺失風險。
- 比選項 1 的儲存空間效率和資料保護較低。
選項 3：將所有磁碟建立為單一 RAID 6
配置
- RAID 6 (4 x 6TB + 4 x 8TB 磁碟)： RAID 6 使用最小磁碟的容量，並保留兩個磁碟的空間作為雙重校驗。此處，所有八個磁碟被視為 6TB 磁碟，因此 (6TB x 8) - (2 x 6TB) = 36TB 可用。
成果
- 可容忍任意兩個磁碟故障以提高資料保護。
- 您可以將所有磁碟組合成單一儲存空間池。
缺點
- 8TB 磁碟的額外容量未被使用（浪費）。
- 可用空間低於兩個獨立的 RAID 5 陣列。
- RAID 6 的寫入效能略低於 RAID 5。
建議
對於大多數使用者，選項 1：為每個磁碟大小建立獨立的 RAID 5 陣列 提供最高的可用容量（在此範例中：18TB + 24TB = 42TB）、簡單的管理，並確保一個群組中的問題不會影響另一個群組。它還充分利用了較大磁碟的額外容量。
如果您最關心的是最高級別的資料保護，並且願意犧牲一些儲存空間空間，請考慮選項 3 (RAID 6)，它可以承受任意兩個磁碟故障。請注意，您較大磁碟上的部分空間將無法使用。
重要： 在設定或更改 RAID 陣列之前，請務必備份您的重要資料。初始化將擦除磁碟上的所有資料。
