Do Solid State Disks Need Defragging?

By Alex Handy

July 15, 2008 — (Page 3 of 4)
Woods did see a scenario in which defragmentation might help, but it’s a different vision than that of Diskeeper. “Another aspect to consider is the benefit of defragging at the file system level. Defragging, independent of the underlying device, will make for more efficient space allocation algorithms in an environment where files are frequently created and deleted, and this could translate into some efficiencies in the I/O subsystem where large blocks of data are written instead of smaller blocks. This may help both HDD and SSDs perform better and last longer.”

Michael Cornwell, lead technologist of Flash and SSD at Sun Microsystems, thinks that Quan’s insistence that free space needs to be defragmented is on target, but that a third-party tool won’t be needed for such tasks.

“The defragmenting of free space on the SSD isn’t the issue. Most current and future generation SSDs will do defragmentation in the background as part of the wear-leveling system. The issue with free space on SSDs has to do with the device knowing what logical blocks are in use by the OS and file system. If the OS can notify the SSD of which blocks [that] are no longer in use, the device can become more efficient with wear-leveling and defragmentation. There is work in several storage protocol workgroups to develop a standard method for a free logical block notification,” said Cornwell.

Clod Barrera, distinguished engineer IBM systems storage, said that Cornwell is on the correct path of reasoning. He said that any data management practices that would increase the speed of access to SSDs would likely become part of the equipment, not part of a third-party defragmentation tool.

“When you go to SSDs, all of these issues kind of go away. What you have in a SSD is an addressable memory space and what you’re doing is you’re mapping a virtual disk onto this memory space. There’s no penalty for having a fragmented disk. In fact, you really have no idea what the real spreading of the data is in a solid-state environment. I can’t imagine what usage environment Diskeeper might be referring to that would require defragmentation,” said Barrera.

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Do Solid State Disks Need Defragging?

By Alex Handy

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