RAID (Redundant Array of Independent Disks) allows multiple drives to be combined together to improve performance, capacity, and/or reliability. For home users, a NAS (Network Attached Storage) system with built-in RAID capabilities provides a versatile way to implement RAID.
There are several common RAID levels to choose from, each with their own mix of benefits. Key factors to consider when selecting a RAID level include: redundancy to protect against drive failures, capacity for storing lots of data, and performance for fast access.
This guide provides an overview of the most popular RAID levels for home NAS systems. We’ll explore the pros and cons of each level to help you choose the right one for your needs. Factors like budget, number of drives, and data protection vs. capacity will be considered. By the end, you’ll have the knowledge to select the ideal RAID setup for your home media server, backup storage, or other NAS use case.
RAID 0
RAID 0, also known as disk striping, spreads data evenly across multiple drives with no parity or redundancy [1]. This allows for increased performance compared to a single drive, as reads and writes can be done in parallel [2]. However, RAID 0 provides no fault tolerance. If one drive fails, all data across the array will be lost. For this reason, RAID 0 is generally not recommended for critical data [3].
The main benefits of RAID 0 are increased read/write speeds and total storage space equal to the sum of all disks. The main downside is complete data loss with the failure of any single drive. RAID 0 works well for non-critical data where performance is the priority over redundancy.
RAID 1
RAID 1, also known as disk mirroring, is a RAID configuration that uses two or more identical drives to create a mirrored set of drives with the same data (1). This type of RAID provides redundancy by writing identical data to each disk at the same time. If one drive fails, the data remains fully intact and accessible on the other disk(s).
RAID 1 requires a minimum of two drives. The usable storage capacity in a two-drive RAID 1 configuration is equal to the capacity of one of the drives. For example, two 4TB drives configured in RAID 1 would have 4TB of usable storage. Adding more mirrored drives does not increase capacity, but can improve read performance.
A key advantage of RAID 1 is excellent read performance, as data can be read simultaneously from both drives. Write performance is slower than a single disk, as data has to be written to both drives. RAID 1 provides good redundancy for home NAS setups while avoiding some of the performance penalties and drive requirements of higher RAID levels.
(1) https://www.reddit.com/r/DataHoarder/comments/m7emsk/raid_redundancy_vs_backup_for_home_nas/
RAID 5
RAID 5 utilizes striping with distributed parity. Parity information is distributed evenly across all drives in the array (Techtarget, n.d.). This provides redundancy so that in the event one drive fails, the data can be recovered from the remaining drives. At least 3 drives are required for RAID 5.
The redundancy of RAID 5 offers good protection against drive failure. If one drive fails, the data can be rebuilt using parity information spread across the remaining drives. According to Ontrack (n.d.), “Having a block of redundancy or parity as part of every data stripe allows the system to rebuild in the event one of the drives fails or goes offline.”
RAID 5 requires a minimum of 3 drives, with most implementations using 3-5 drives. More drives can be added to increase capacity, but the redundancy remains at just one drive worth of space (Medium, 2019). The tradeoff with RAID 5 is that more parity information needs to be calculated and written than with RAID 1, which can impact performance.
RAID 6
RAID 6, also known as double distributed parity, offers better redundancy than RAID 5 by using two parity drives instead of one. This allows the array to sustain multiple drive failures while still protecting data. At minimum, RAID 6 requires 4 drives to implement – 2 for parity and 2 for data (though more drives are recommended). The tradeoff is that RAID 6 write speeds will be slower than RAID 5 since calculations need to be performed across 2 parity drives. However, for home NAS setups where storage space is more important than performance, RAID 6 provides excellent protection against drive failures. As suggested by this Reddit discussion, RAID 6 is preferable over RAID 5 in most home scenarios.
RAID 10
RAID 10 (also known as RAID 1+0) combines both striping and mirroring for increased performance and redundancy. With RAID 10, data is both striped (spread evenly across multiple disks like in RAID 0), as well as mirrored (duplicated on a second set of disks like in RAID 1) (Source). This provides the speed benefits of RAID 0 striping, along with the redundancy of RAID 1 mirroring.
RAID 10 requires a minimum of 4 drives to implement since data is both striped and mirrored. The storage capacity of RAID 10 is equal to the capacity of the smallest drive times the number of drive pairs (so 2 pairs of 2TB drives would yield 4TB of usable storage). While RAID 10 has significant overhead compared to RAID 5 or RAID 6, its combination of performance and redundancy make it a popular choice for critical applications that require both (Source).
Choosing Drives
When selecting drives for a home NAS, one of the biggest considerations is whether to use traditional hard disk drives (HDDs) or solid state drives (SSDs). HDDs have historically been much cheaper per gigabyte of storage, but SSD prices have been falling rapidly. As of mid-2023, 2TB SATA SSDs can be purchased for around $150 while 6TB NAS HDDs cost approximately $130. The price per terabyte for SSDs has become quite competitive with HDDs.
SSDs have several advantages for use in a NAS. They are much faster, with dramatically higher read/write speeds and lower access latency. This results in snappier performance for accessing files and running applications on the NAS. SSDs consume less power, generate less heat, and make no noise since they have no moving parts. They are also more reliable and durable, with typical mean time between failures (MTBF) ratings exceeding 1 million hours compared to around 1 million hours for NAS HDDs.
However, HDDs have the advantage of much higher storage density per dollar spent. For very large storage capacities, HDDs remain significantly cheaper than SSDs. High capacity HDDs in the 10-16TB range can often be purchased for $200-300 while comparable capacity SSDs are over $1000. Home users needing massive storage for media files and backups may still prefer using HDDs to maximize storage at a reasonable cost. One compromise is to use a small SSD for the OS and applications, and large HDDs for bulk storage.
Overall, SSDs are the superior choice for performance and reliability. But HDDs can’t be beaten on price per terabyte for high capacity storage. Users need to weigh their specific performance, capacity, and budget requirements when choosing drives.[1][2]
Expanding Storage
One advantage of software RAID is that it allows you to easily expand your storage over time by adding more drives. For example, you can start with 2-4 drives in a RAID configuration, and add drives later as your storage needs grow. Many NAS devices make it simple to add drives and expand the storage pool or volume (Source: https://www.reddit.com/r/qnap/comments/sgeuk8/nas_almost_full_how_to_expand_it/).
Another way to expand capacity is to migrate to larger drives over time. For example, you could start with 8TB drives, then later replace them with 14TB drives. Most NAS software allows you to replace drives one at a time without losing data. This enables gradually migrating to higher capacity drives as needed (Source: https://kb.synology.com/en-ph/DSM/help/DSM/StorageManager/storage_pool_expand_add_disk).
Software vs Hardware RAID
When choosing between software and hardware RAID, there are pros and cons to consider for each option:
Software RAID uses the system’s CPU and RAM to perform RAID calculations and data transfers. The main advantages of software RAID are:
- Flexibility – software RAID allows you to choose from various RAID levels and allows drives to be easily migrated between systems.
- Cost – software RAID doesn’t require additional hardware, so it is less expensive to implement.
However, software RAID has some disadvantages:
- Performance overhead – the CPU has to handle RAID tasks, which can impact performance.
- Lack of caching – most software RAID doesn’t have a battery-backed cache, which can impact write speeds.
Hardware RAID uses dedicated RAID cards that handle all RAID computations and disk I/O. The main benefits of hardware RAID are:
- Faster performance – hardware RAID offloads processing from the CPU and often includes caching and other optimizations.
- Increased reliability – hardware RAID includes redundancy features like battery-backed cache to prevent data loss.
The downsides of hardware RAID include:
- Higher cost – RAID cards add to the overall system cost.
- Less flexibility – hardware RAID makes it harder to migrate drives between systems.
Overall, hardware RAID performs better while software RAID is cheaper and offers more flexibility. For home or small business NAS use, software RAID is often sufficient, though some may still opt for a hardware RAID card for the performance gains if the cost is manageable.
Conclusion
When choosing the best RAID setup for your home NAS, the most important factors are your budget, storage space needs, and data redundancy requirements. If budget is a primary concern, RAID 0 provides great performance without redundancy at the lowest cost. For redundant data protection, RAID 1 or RAID 10 are good options that mirror data across drives. RAID 5 provides a balance of redundancy and storage capacity, while RAID 6 offers the highest level of redundancy for critical data.
For most home users, RAID 1 or RAID 5 will provide a good combination of performance, storage capacity, and data protection. RAID 10 is recommended for higher performance needs. Make sure to use enterprise-grade NAS drives rated for 24/7 operation. Plan ahead and allow room to expand your array as your storage needs grow over time. With the right RAID setup, you can build a fast and reliable home NAS tailored to your budget and requirements.
