RAID 4 or 5 - Which Is Better?
The Redundant Array of Independent Disks (RAID) is a storage strategy widely utilized by IT professionals and businesses to enhance performance, ensure data parity, and provide redundancy. There are several RAID configurations, each denoted by a numerical label such as 0, 1, 2, 3, 4, and so forth, with each type offering its own approach to data storage and processing.
Focusing on RAID 4 and RAID 5, these are two distinct but closely related RAID configurations. Both are designed to improve performance, though the actual efficiency depends on the specific setup of the array. In this article, we will delve into a detailed comparison and analysis of RAID 4 and RAID 5, highlighting their similarities and differences. A key point to note is that both RAID types incorporate parity, but they implement it in different ways.
What is RAID 4
RAID 4 utilizes block-level striping with a unique setup that includes a dedicated parity disk. This RAID configuration, first developed by tech specialists at Berkeley, is complex and best implemented with SSDs for notably faster data transfers.
A significant benefit of RAID 4 is its ability to expand storage online without recalculating parity, although any disks added must be entirely devoid of data. In RAID 4, each disk operates independently, and data is distributed across the disks in blocks of varying sizes.
The independent operation of disks in RAID 4 allows for parallel processing of I/O requests, which can enhance performance depending on the specific application. However, because RAID 4 uses a single disk for parity, its performance speeds are generally not as high as those offered by RAID 5.
Disadvantages of RAID 4:
- Uses one single drive for parity, and this reduces the speed to an extent compared with other RAID types.
- The setup is a bit complex, not many people prefer it over RAID 5
- Small file requests run slowly on RAID 4 because data needs to be stripped in blocks and transmitted in parallel.
Advantages of RAID 4:
- You only need a minimum of two disks to set up RAID 4: one disk for data stripping and another for parity. This makes RAID an affordable alternative for some people.
- RAID 4 provides faster performance when handling large sequential files than small random files.
What is RAID 5
RAID 5 is a type of RAID setup that equally supports block data striping and parity. But unlike in RAID 4 where a single parity drive is used, in RAID 5, parity data is spread across the disks in the array. This cross-sharing of parity data makes RAID 5 offer a seemingly better performance coupled with higher transfer speeds.
Also, since there is no single parity drive that may fail, RAID 5 can handle drive failures without your files getting lost. When a single drive drives in RAID 5, subsequent reads can be calculated from the distributed parity; don’t mistake this for data backup, if another drive fails, you could lose everything.
To set up a RAID 5 array, you need a minimum of 3 disks. RAID 5 could feature many data layouts, depending on how data is written across the disks. RAID 5 is generally faster than RAID 4 because of the distributed parity; a single parity disk can create a data input bottleneck, which is a common problem with RAID 4.
What is RAID 5? Learn more!Disadvantages of RAID 5:
- RAID 5 has a write penalty calculated to be four. This is because, RAID 5 reads the data on the drives, then goes on to read the parity, returns again to write the data, and finally, writes the parity; four operations for each effective one
- When rebuilding RAID 5, you’ll notice a significant performance decline, especially when disks of different sizes are used.
Advantages of RAID 5:
- RAID 5 can handle single drive failure perfectly; the RAID will attempt to read the lost data from the distributed parity data.
- Due to its distributed parity technique, there’s more space for primary data to be stored across all drives used in the array.
- RAID 5 replaced RAID 2 to 4 and provided the footprint for modern-day RAID levels. It offers better performance and redundancy than RAID 2 to 4.
Comparison Table RAID 4 vs RAID 5:
These two RAID levels compare to one another in many ways and below is a table that makes it clearer to understand their differences.
Comparison | RAID 4 | RAID 5 |
Storage Pattern | Block-stripping | Block-stripping |
Parity | Single disk parity | Distributed parity |
Minimum No. of Disks | 2 | 3 |
Cost of Set Up | Affordable | Affordable |
Modern Relevance | Obsolete | Not obsolete but rarely used |
Performance and Speed | Decent | Better |
Fault Tolerance | Single disk failure | Single disk failure |
Best Application | High data transfer tasks | High data transfer tasks |
A single drive failure will reduce the performance of RAID 4 and RAID 5, and if another drive goes on to fail before you could rebuild the RAID or replace the first damaged disk, then you’re SCREWED. The dedicated parity disk on RAID 4 slows down write speeds but does not affect read speeds.
Data Recovery Differences in RAID 4 vs RAID 5
In RAID 4, the failsafe information stored in the parity disk is only ever retrieved when one of the data disks fails. For the rest of the time (when all drives are in good condition), RAID 4 will only read from volumes on the data disks, which makes it perform faster – up to 20% better than RAID 5, especially when SSD or NVMe drives are used.
In RAID 5, the parity information is written into the same drives where the primary data is saved. Now, because the parity data is saved on the data disks, RAID 5 takes a little more time to read data from the drives because it needs to read the parity information too, which actually is not important until there’s a failed drive in the array.
But then, regardless of the RAID level you choose to set up, you should never play down the role of regular backups. Fault tolerance and parity data calculations do not equate to backup, peradventure multiples disks fail at once in the array, your entire data in the RAID is screwed – with minimal possibility of getting them back.
How to Safeguard Your Vital Data?
You should also monitor the health status of the disks in your RAID array to know when they start going bad, so you can fix or replace them on time. But then, the best way to ensure that your important files and data are safe and preserved is by backing them up externally – to a cloud storage or another local storage.
Regular data backups provide you with the safest failsafe haven to fall back on in times of data loss. So, even if multiple disks fail at the same time in your RAID array, you’re sure your vital data are still retrievable – from backup. A reliable RAID backup solution for Windows OS users is DiskInternals RAID Recovery software.
DiskInternals RAID Recovery
This software lets you clone your RAID drives in disk image format and the image files to serve as your backups. You can create multiple disk images at any time – for free. It doesn’t stop there, the DiskInternals RAID Recovery is primarily a data recovery solution for RAID users; it can recover data from any RAID array and it supports a wide variety of RAID controllers.
RAID repair utility runs on all Windows OS versions and utilizes very minimal system resources. The interface is intuitive and there’s a wizard interface that guides you through recovering your lost RAID data using this program. Whether your RAID disk got dead or the controller is damaged, DiskInternals RAID Recovery can help out.
Conclusion
Literally, in all respects (aside from how they store and deal with parity data) RAID 4 and RAID 5 are identical. If you must choose between these two, RAID 5 is a better option. However, you may love to consider RAID 6 or RAID 10, which tend to offer higher levels of redundancy and performance.