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Striped volumes
A striped volume is usually a type of volume used to provide high performance and availability. Striped volumes get their name because they divide data across multiple disks, or stripes. They are often used as the bottom of a storage stack because they have advantages over other storage types in terms of redundancy and performance. When you use a striped volume, data is split up into fixed-size segments called blocks, and each block is assigned to an individual disk in the storage array. When a file is stored in a striped volume, the file data are written to multiple blocks that exist on different disks. As an example, if you had an eight-disk striped volume with four disks containing two disks each, then a particular file would be written to all four disks.
The result of this writing technique is that a striped volume can read or write data to two disks at the same time, which means it can be two times quicker than a non-striped volume. This is not true for writes because the technique used to write data to a striped array means that while four disks are being written, another stripe has to be read and therefore a “Disk Input Queue Length” metric may report high latency. Also, a striped array cannot be used for mirroring or asynchronous logging because you cannot write to two locations at the same time.
Spanned volumes
A spanned volume is a type of volume that can be used to provide high performance and availability. Spanned volumes get their name because they span physical space across multiple disks, or stripes. A spanned volume can be seen as a logical extension of the striped volume. When you use a spanned volume, data is written to random-sized blocks across the disks in the storage array. As an example, if you had an eight-disk spanned volume with four disks containing two separate sets of four disks, you could store each set of four disks on one of the two disks. By using a spanned volume, you can provide performance improvements versus using a single-disk logical volume.
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Title:Using Storage Spaces to Create a Spanned Volume: Step-by-Step Guide [ARTICLE START]
Spanned volumes let you take advantage of the High I/O performance and availability that are available for disk arrays in Windows Server 2012 R2. With spanned volumes, you can create logical volumes in Windows Server 2012 R2 and assign them to a pool. Then, you can add the hardware that supports the logical volumes to that pool of disks, and Windows will be able to balance I/O across all of the disks in the pool. When data is inserted into the spanned volume, it’s written across the disks in a striped fashion. The data blocks in a striped fashion are written sequentially from one disk to another disk. A spanned volume can also be created using a set of physical disks in System Center 2012 R2 Virtual Machine Manager (VMM).
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Title:Understanding Spanned Volumes in Windows Server 2012 R2 [ARTICLE START]
Pros and cons of each
A striped volume has advantages over everything but a spanned volume, such as the fact that if you were to lose two disks in the storage array and you had one disk left, it would still be possible to recover the data because you have multiple copies. The other advantage of a striped volume is that all of the disks in a stripe can be used to store more than just one file, as long as your program allows for it. A spanned volume, on the other hand, has fewer advantages over a striped volume. The primary advantage of a spanned volume is that each logical disk in a spanned volume is treated as though it were its own physical disk. This means that if you have one logical disk and one physical disk in a spanned volume, and you lose one physical disk (and can’t recreate the data on a new physical disk), you still have access to all of the data stored on that volume. However, this also means that your volumes are more closely linked to the individual disks in your storage array than they would be if they were striped. For example, if a raid array is formatted as one large volume with one stripe per physical disk, then all of the data maintained by that array is spread across all of those disks. In this case, if one physical disk fails, then that array loses the data stored on it. If a spanned volume were to fail, on the other hand, the RAID controller would not lose any of the data from all of the disks in the volume. However, if you wanted to make changes to a file maintained by a spanned volume, you would have to recreate all of those files on different physical disks. This is where striped volumes have an advantage over spanned volumes. If you were to make changes to a file maintained by a striped volume, you would have to recreate that file on multiple physical disks. However, you would be able to access all of the data maintained by your array even if one physical disk in your array failed.
When to use one or the other
Striped volumes are usually used as the bottom of a storage stack, or stackable storage. The reason they are used as the bottom of a storage stack is because they are less expensive; however, there are occasions when spanned volumes might be better. When you have high-end servers with lots of memory and CPU power that want to use high levels of performance, you might consider using a spanned volume, since it takes advantage of all the memory and CPU power that is available in the server. An example of when you would not want to use a spanned volume is when you have a large number of small files (for example, image files from cameras and scanners), and you want to run them in parallel to get performance. For this reason, it is better to use striped volumes on your storage system than spanned volumes.
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– SANS for the DC Pro (now the DC) exam: http://www.sans.org/critical-security-skills/skills/storage/confidential-data-management/index.php
– SANS for the GIAC Certified Forensics Analyst (GCFA) exam: http://www.sans.org/critical-security-skills/skills/forensics/index.php
– SANS for the GSEC exam: http://www.sans.org/critical-security-skills/skills/jobsite-security/index.php
– SANS for the GIAC GSEC exam: http://www.sans.org/critical-security-skills/skills/general-security/index.php
– SANS for the GIAC Security Essentials exam: http://www.sans.org/critical-security-skills/skills/generalist/#learn_security_essentials_course
How to create a striped or spanned volume in Windows 7
Creating a striped or spanned volume in Windows 7 is easy. All you have to do is open Computer Management, select the Disk Management node, right-click on Disk Management in the left pane, and select Create Striped Volume or Create Spanned Volume. Then, you can specify whether you want to create a striped volume or a spanned volume on one of the disks in your storage array. Once you have done that, Windows 7 will automatically create the striped or spanned volume for you.
Striped Volume
A striped volume is used to spread data across multiple disks in a storage array. This improves disk performance because it distributes the workload over multiple disks. Windows 7 should automatically format any data drives that you add to a new computer as a striped volume. You can also manually create striped volumes on individual hard drives. To do this, open Computer Management, select the Disk Management node, right-click on Disk Management in the left pane, and select Create Striped Volume. Then, you can specify the size of your striped volume.
The following screenshot shows a simple example of a striped volume. Note that you can use any type of disk for your striped volumes, including SSDs. It is a good idea to use SSDs for these disks because SSDs have much faster I/O performance than HDDs:
