Disks

Implementing Disk Quotas

Disk Quotas can be configured from the command line or through scripts using the Fsutil administrative command-line tool. In the previous article Disk Quotas we have seen how configure disk quotas using the GUI. Windows 7 rich feature set of command-line utilities include the quota functionality within Fsutil and can be used as follows:

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Disk Quotas

Disk Quotas allows administrators to control how much of a volume users can fill with files. Although, disk quotas are normally implemented on servers that hosts shared folders they can also be implemented on standalone computers running Windows 7. In a scenario where multiple users access a single computer, a single user may completely fills a volume with his/her files hence, preventing others from saving their files due to lack of storage space.

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Windows 7 does not support software RAID-5

The software based striped volume with parity (Raid-5) is not supported in Windows 7. However, Windows 7 do support hardware-based RAID using a hardware raid controller. This is by design according to Microsoft Technet Forums and considering that hardware-based RAID performs much better and has additional features, I tend to agree with Microsoft not to overload the system with additional cpu-intensive activity. What I don’t understand is why the option is there but not usable – it’s grayed out! Even, the Diskpart command line tool has a create volume raid option but if you try out, it returns – The command you selected is not available with this version of Windows.

Hardware RAID-5 offers failover protection and performance improvement.  RAID-5 writes data in small blocks or stripes on three or more disks simultaneously.  A stripe of data across all disks participating in the set consists of the actual data and parity information. Parity information is not stored on the same disk but distributed among the disks. In fact, RAID-5 is sometimes referred to as Striping with Distributed Parity.

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How to create a Mirrored Volume

In simple terms, a mirrored volume (RAID-1) writes the same data on two disks or partitions of separate disks. That is, any changes to data (or new data) made to the first disk of the mirror set are also made to its mirror disk. Mirrored volumes require at least two disks or two free partitions on separate disks. The free partitions or disks need to be of the same size, otherwise, the mirrored volume size would be equal to the smallest partition or disk.

The main advantage of mirrored volumes is disk drive redundancy. It provides availability of data in case one disk drive fails while it can mirror a system disk containing the operating system.  If a disk fails, the mirror set continues to operate on the remaining disk. The recovery operation of the mirror set depends on which disk fails if the set contains the system disk.  In general you would break/remove the mirror set, replace the faulty disk and re-create the set.

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How to create a Striped Volume

A striped volume (RAID-0) writes data in small blocks or stripes on two or more disks simultaneously. To create a striped volume you require at least two disks, however, having more than two disks participating in the striped volume will enhance further data access performance. That is, when data is written or read from a set of disks simultaneously the I/O bandwidth increases and hence, achieving better read and write transfer speeds. When creating a striped volume, the volume size is dependent on the disk with the smallest free space, as the portions of the disks included in the set need to be of the same size. I suggest to use full disks of the same size when creating striped volumes, otherwise, you end up with free spaces on some disks! While, the disks of a striped volume need to be converted to dynamic, remember that such volume is not fault-tolerant. If one disk fails, the entire volume fails.

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How to create a Spanned Volume

A spanned volume is a volume that uses more than one physical disk. You can use any unallocated space left on disks to create a spanned volume. It also can include more than one unallocated space on a single disk while free spaces can be of any size. The only benefit of spanned volumes is the use of unallocated space that may have originated from imported disks or specific volume arrangements. The main disadvantage is the risk of losing the volume if one disk participating in the spanned volume fails. A faulty portion means a faulty spanned volume! There are no performance benefits when implementing spanned volumes.

To create a spanned volume, perform the following steps with administrator privileges:

1. Open the Disk Management console by typing disk management in the Start search text box and click Create and format hard disk partitions or from the Computer Management console found in Control Panel\All Control Panel Items\Administrative Tools
2. Convert disks to Dynamic if they are set as Basic, right-click a Disk (left-hand side) and select Convert to Dynamic – at a later stage, the wizard prompts you to convert disks if you skip this step Read more…

How to create a Simple Volume

In Windows 7 (and Vista) simple volumes are created on basic disks with or without partitions and on dynamic disks when no other disks are available to form a stripe set or spanned volume. Therefore, it is the default volume type that has the basic features such as, extend and shrink volumes! It is recommended to use basic disks with simple volumes if you do not require the advanced features of dynamic disks.

To create a simple volume, follow these steps with administrator privileges:

1. Open the Disk Management console by typing disk management in the Start search text box and click Create and format hard disk partitions or from the Computer Management console found in Control Panel\All Control Panel Items\Administrative Tools
2. Right click an unallocated space on the new disk and select New Simple Volume – the New Simple Volume Wizard starts
3. Specify the volume size in MB – the default is the maximum available space
4. The next screen shows the default assigned drive letter, you can set any available letter from the drop-down list, while, you can also create a volume without a drive letter or mount it in an empty folder
5. In the next format partition screen, it is recommended to leave the default file system and allocation unit size settings while type in a meaningful name in the volume label text field. If you suspect that the drive may contain bad blocks I suggest you perform a long format (uncheck the Perform a quick format), otherwise do a quick format as the process may take very long especially with large capacity drives. Also, you can enable file and folder compression for this volume
6. The final screen is a summary of all set parameters, if no changes are required click Finish

When using the DiskPart command-line tool make sure that you create a partition on a basic disk while a simple volume on a dynamic disk, otherwise the tool fails. The Disk Management snap-in is more intelligent and adjusts itself according to the disk type.