Frequently Asked Questions

Chances are, others have the same questions that you do. Therefore, we have taken the common questions for Diskeeper, Sitekeeper and Undelete and provided the answers (and the questions) below in our Frequently Asked Questions section. Simply select the product below that you have questions about. If you can’t find the answer you’re looking for, you can submit a tech support question here.

Diskeeper | Sitekeeper | Undelete

Question
Will Diskeeper enhance the performance of my disk array (SAN, RAID, stripe set, etc.)?
Answer
Yes, automatic defragmentation with Diskeeper can significantly enhance the performance of a disk array. Multi-disk arrays, such as RAID 5 arrays, are seen by the operating system as a single disk, known as a virtual disk. The operating system builds a master file table (MFT) that arranges files on the virtual disk and requests data from the RAID controller based on its layout in the MFT. If a file is fragmented into several pieces, the OS must make multiple I/O requests, one to retrieve each chunk (or fragment) of data from the disk. A common misconception is that fragmentation does not affect a disk array because files are stored across multiple drives. It’s important to remember that, even on a single drive, the physical layout of the drive is different than the logical layout of the drive. At the logical level, the disk is represented as a series of contiguous blocks. This is the “picture” that the disk presents to the operating system. At the physical level, factors such as multiple heads and platters, rotation of the disk, etc., determine how blocks of data are placed for optimal retrieval speed; blocks that are logically contiguous may not be physically next to one another (in fact, they probably won’t be). Likewise, with a disk array, the physical placement of the data blocks is not important as far as Diskeeper is concerned. The disk array controller handles all that; the operating system sees a single logical drive (the virtual disk). Therefore, disk arrays see the same benefits from automatic defragmentation with Diskeeper as do single drives.

Question

Will Diskeeper enhance the performance of my disk array (SAN, RAID, stripe set, etc.)?

Answer

Yes, automatic defragmentation with Diskeeper can significantly enhance the performance of a disk array. Multi-disk arrays, such as RAID 5 arrays, are seen by the operating system as a single disk, known as a virtual disk. The operating system builds a master file table (MFT) that arranges files on the virtual disk and requests data from the RAID controller based on its layout in the MFT. If a file is fragmented into several pieces, the OS must make multiple I/O requests, one to retrieve each chunk (or fragment) of data from the disk.

A common misconception is that fragmentation does not affect a disk array because files are stored across multiple drives. It’s important to remember that, even on a single drive, the physical layout of the drive is different than the logical layout of the drive. At the logical level, the disk is represented as a series of contiguous blocks. This is the “picture” that the disk presents to the operating system. At the physical level, factors such as multiple heads and platters, rotation of the disk, etc., determine how blocks of data are placed for optimal retrieval speed; blocks that are logically contiguous may not be physically next to one another (in fact, they probably won’t be). Likewise, with a disk array, the physical placement of the data blocks is not important as far as Diskeeper is concerned. The disk array controller handles all that; the operating system sees a single logical drive (the virtual disk). Therefore, disk arrays see the same benefits from automatic defragmentation with Diskeeper as do single drives.

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