Simple, Spanned, Striped, or Mirrored Volume: How They Are Different?

A disk volume is the storage unit created when a disk is formatted or partitioned with a desired file system. It is the point where the storage device is ready to store the data.

It can combine multiple disks and is managed by the operating system. Volumes can be restored to defaults or formatted with multiple file systems such as exFAT, FAT32, or NTFS. An NTFS volume type is the one accepted by Windows, while others, such as exFAT or FAT32, are universal allocation types. 

A volume can be created in multiple ways. How the volume is created in itself is a very big topic to talk about. Volumes play a very crucial role in data optimization, and their efficient access ensures that the system runs smoothly. 

This article will provide you with the basic knowledge about different types of disk volumes and how they differ from each other in terms of their functions. The article will also guide you through the advantages, disadvantages, and ideal cases where these types should be used.

Also Read: What is RAID?

If you want to create a striped, spanned, or mirrored volume, you will need to convert the basic disk into a dynamic disk. So let’s first understand what basic and dynamic disks are and how volumes are created in both of them.

Basic Disk vs Dynamic Disk

Basic Disk

Basic Disk includes traditional types of partitioning that support Primary, Extended, and Logical partitions.

• Partition Types – Primary, Extended, Logical
• Partition Table uses – MBR/GPT

MBR structure and pros/cons

GPT structure and Pros/Cons

How is Volume created?

• We initialize the disk (not volume but entire disk), choosing MBR or GPT.
• When we partition the disk, we make an entry into the partition table. That entry includes all the portions of the disk/ blocks of sectors belonging to the particular volume we want to create.
• No data or anything is moved; only the metadata describing where the volume starts and where it ends.

Taking the Example of MBR (512 Bytes size)

1. [446 bytes] Bootloader code (It helps in system booting)
2. [64 bytes]  Partition table (4 entries × 16 bytes) (Volume details are stored)
3. [2 bytes]   Boot signature (0x55AA)

• In those 64 bytes, a partition table is maintained with 4 entries of 16 bytes each. Those four entries allow us to create either 4 primary partitions or 3+1 primary + extended partitions. In the above image, we have created 2 Primary and 1 Extended partition for dual-booting systems. 
• The primary partition is created the moment an OS is installed. Then, from the rest of the space, every time we create a volume, the partition table maintains the logical addresses (start and end) of the volume. 

Note: The disk is not actually divided, just the addresses are mentioned to make a difference. 

• Now, this is a case of simple volume in a Basic Disk type.

Dynamic Disk

A dynamic disk includes an advanced disk partition that enables the use of multiple disks.

• Partition Types – Simple, Spanned, Striped, Mirrored
• Partition Table uses – LDM

How is dynamic volume created? (Simple, Spanned, Striped, or Mirrored)

Note: Windows Home doesn’t support dynamic volume creation.

• The first and foremost step is to convert the basic disk to a dynamic disk. In this step, Windows creates an LDM database of size 1MB at the end of the disk. (Kept Hidden). The entire MBR/GPT partition logic is replaced by LDM. 
• Now, the user requests the system to create a new (simple, spanned, striped, or mirrored volume). Disk management commands the LDM services.
• LDM allocates one or more contiguous ranges of block addresses on one or more disks. For simple volume, a single extent on the disk. For spanned or striped, multiple extents across disks.
• Each extent has the following information as metadata.

1. Disk ID
2. Starting Sector
3. Total number of sectors included

• LDM captures overall information in the form of metadata to record it in a database. The information includes

1. Disk ID
2. Volume Type
3. Extent information
4. Volume Size and State
5. Other attributes (fault tolerance, flags etc.)

• The metadata is replicated to the LDM database of all the disks involved in the volume.

1. Simple Volume 

A simple volume is what people consider most of the time. A single dynamic drive is occupied to create a simple volume. The space taken from the drive can be continuous or non-continuous. For instance, if the memory location 452 is allocated, the next location allocated does not necessarily need to be 454; it can take any other memory location from the disk. More partitions can be created to organize the data in a much better way.

How is it created?

Using MBR (For Windows Home Edition)

Explained above.

Using LDM (For Windows Pro and Enterprise Edition)

Explained above.

An overview of a simple volume of Basic Disk vs Dynamic Disk

Advantages, Disadvantages, Ideal Use Case

Advantage: On a simple volume, it is easy to create and manage the data. Simple volume is optimized and efficient for a system with a single disk. 

Disadvantage: The main disadvantage of simple volume is that it is limited by the capacity of a single disk. 

Ideal use case: It is good for the storage of operating systems. It can also be used in gaming consoles as game storage. 

2. Spanned Volume

A spanned volume is a dynamic volume allocation where the volume created is the combined storage capacity of multiple disks (two or more). These disks are required to lie in a contiguous disk region. It is the work of the array manager to sequentially allocate space on multiple disks. Once the current disk is full, the allocation continues to the next disk and so on until the volume size required is fulfilled. 

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How is it created?

A spanned volume combines unallocated space from two or more disks into one logical volume.

Storage Taken:

• Disk 1: Block 1-40 used.
• Disk 2: Block 2-60 used.
• These blocks are joined into a single spanned volume.

Data is written on the respective disks in a sequential manner. Writing in Disk 2 happens only when Disk 1 is filled up.

Advantages, Disadvantages, Ideal use case

Advantage: A major advantage of the spanned disk is that it can be extended if required. 

Disadvantage: The major drawback of the spanned disk is the continuous disk allocation. If one disk fails, the entire data is lost, even if a portion of it is stored on the other disk. The head pointer deletes the entire data. Apart from that, there is no performance improvement in considering the Scanned volume. 

Ideal use case: Spanned volume is ideal when the user needs a larger storage pool for their data without requiring redundancy. 

Note: To protect the spanned volume against disk failure, you can mirror the entire spanned volume onto another storage. It helps the original spanned volume recall the data from the mirrored volume whenever it fails. 

3. Striped Volume 

Striped volumes (Raid 0) are logical unit spaces created by taking free spaces from multiple disks. While the idea is similar to spanned volume, a striped volume writes data in all disks simultaneously, providing the maximum speed. When the data arrives to be saved in a striped volume, it is divided into small chunks known as data blocks. These blocks are evenly distributed across all the disks in the striped volume. Unlike spanned where data was saved one after another, in striped volumes, all the data blocks are written to the disk in parallel at the same time. This allows for the parallel execution of tasks, eventually leading to faster performance. 

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How It’s Created

Let’s suppose we have Disk 1 and Disk 2.

Storage Taken:

• Block 1 → Disk 1
• Block 2 → Disk 2
• Block 3 → Disk 1
• Block 4 → Disk 2
• And so on…

This stack-by-stack interleaving is called striping.

The volume size is the sum of all striped parts (e.g., 10 GB + 10 GB = 20 GB).

In striped volume, the data is not sequentially filled — it’s striped alternately.

Advantages, Disadvantages, Ideal Use Case

Advantage: Due to parallel reading and writing, a striped volume increases efficiency for others.

It also utilized the full capacity of the disk. 

Disadvantage: Since the data is written to multiple disks similar to spanned volumes, there is no fault tolerance. i.e., if one disk fails, the entire data is lost. 

Ideal use case: Spanned volumes are mostly used in high-performance tasks like gaming or video editing that require high-speed data access. 

4. Mirrored Volume

The mirrored volume, also known as RAID 1, is a storage setup where data is duplicated across multiple disks. It is a fault-tolerant storage setup. In case of a disk failure, the system won’t be interrupted and will continue running using the mirror copy. 

For instance, if there are two disks, disk A and disk B, and data arrives to be written in the, every file saved is copied to both disks. If disk A fails, the system will instantly switch to disk B. 

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How is it created?

Let’s say, we have Disk A and Disk B

Storage Taken:

Disk A: Block 1-100

Disk B: Block 1-100

When a mirrored volume is created, an equal number of blocks is taken from both disks from the same locations. This idea of replicating all information is called Disk Mirroring.

Note 1: If it is extended in Disk A, for instance, from 20 GB to 30 GB, Disk B is also extended with the same space, so that bit-for-bit mapping is ensured.

Note 2:Every write operation is split into two identical writes, writing to both the disk simultaneously. If either write fails, the entire write operation fails.

Note 3: Reading can be done from any of the disks. It’s the choice of windows that mostly prioritizes the disk with lower latency.

Advantages, Disadvantages, Ideal Use Case

Advantage: Since a mirror copy of data is created, mirrored volumes are fault-tolerant. The reading of data is faster since the system can take the data from either disk. 

Disadvantage: The disadvantage of a mirrored disk is the slower write time since the data is required to be written twice. Another drawback of a mirrored disk is that it wastes 50% of the storage, hence a relatively costlier option to choose.

Ideal use case: The mirrored volume is used for OS installation, where there is no scope for downtime. It can also be used in the case of small servers that need some fault tolerance. 

Conclusion

The choice of the right disks always depends on the specific needs of the user. Some users aim for maximized storage, while some ensure data safety first. A normal user who needs the disk for day-to-day storage can go with the simple volume since it is best for standalone use. Spanned volumes offer more flexibility as the storage is expandable. Striped volume is efficient, and mirrored volume makes sure that there is no data loss. An understanding of these differences can help you make a better decision in choosing a volume type for your needs.