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Tuning IT resources almost always involves some sort of tradeoff. When overclocking a CPU, for instance, reliability issues eventually trump performance gains. However, when it comes to maximizing the lifespan of your flash memory storage, one of the best things you can do is to focus on achieving the best possible performance. Many of the same activities that improve storage performance also improve flash storage longevity.
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Flash drives store data on cells within the drive's flash memory chips. These cells can be read over and over again without impacting the drive's reliability. However, there is a limit to the number of times data can be written to a cell. As such, the key to improving a flash drive's longevity is to minimize write operations, which also helps to improve overall performance. Enterprise-class flash drives have proven themselves to be extremely reliable. Even so, taking steps to reduce write operations further improves the drive's longevity and performance.
Tip 1. Avoid parity schemes for flash memory storage
One of the most important things you can do with regard to drive lifespan is to avoid using flash drives in parity schemes such as RAID 5 and RAID 6. Although this parity data provides a degree of protection against disk failure, it does so at the cost of diminished array performance and reduced storage capacity. In the case of flash storage, the write operations associated with parity data can also decrease the drive's longevity. Instead, it is more effective to use a mirrored stripe set (RAID 1+0). Doing so protects against disk failures without the unnecessary write cycles.
Tip 2. Disable defragmentation
Another recommendation is to disable defragmentation for flash drives or flash arrays. The defragmentation process was originally intended as a way to improve performance by limiting hard disk head movements. However, flash drives do not incur a performance penalty related to the time it takes to move a mechanical head. Furthermore, wear leveling mitigates any benefit that might be derived from defragmenting a flash drive.
Most modern operating systems (OSes) automatically disable defragmentation for solid-state storage. However, a number of situations can cause the defragmentation process to run automatically, even if the OS is designed not to defragment flash storage. For example, if the OS is unable to identify a drive as solid-state -- such as when a generic SSD is used -- it generally assumes the disk is non-flash. Similarly, virtual hard disks are often treated as a hard disk even if the underlying physical storage is flash-based.
Tip 3. Disable Windows pagefile
Another thing you may be able to do to improve the longevity of flash memory is to disable the pagefile for any OS volumes that use flash storage. The Windows pagefile exists primarily as a mechanism for overcoming RAM limitations and storing crash dump information. Depending on how your systems are configured, you may be able to disable the pagefiles completely or move them to non-flash volumes.
Disabling the Windows pagefile has been hotly debated for decades, but a recent Microsoft TechNet article refers to the pagefile as optional, and changes that have surfaced in the Windows 10 preview suggest the pagefile is becoming much less important than it once was.
Tip 4. Avoid dynamic wear leveling for static data
One last bit of advice is to avoid storing static data on disks that use dynamic wear leveling. Wear leveling extends the life of flash drives by distributing write operations across the drive rather than allowing the same cells to be written to repeatedly. Wear leveling can be static or dynamic.
Imagine for a moment that a flash drive is filled to 50% capacity with static data, and that highly transactional data is frequently written to the remaining 50% of the drive. If the drive uses only dynamic wear leveling, the cells containing active data are wear leveled. This means the very presence of static data causes the drive to wear unevenly. Wear leveling causes the drive to last longer than it would if no wear-leveling mechanism were present, but the frequently written cells eventually wear out and cause the drive to fail even though the cells containing static data may be practically brand new.
Static wear leveling works similarly to dynamic wear leveling, except the static data is periodically relocated to different cells so the drive can be wear leveled more evenly. This improves the drive's overall longevity.
Although SSDs are generally reliable, taking steps to further improve the reliability of your flash memory can help to reduce the organization's long-term storage costs.
About the author:
Brien M. Posey, MCSE, has received Microsoft's MVP award for Exchange Server, Windows Server and Internet Information Server. Brien has served as CIO for a nationwide chain of hospitals and has been responsible for the Department of Information Management at Fort Knox. Visit Brien's personal website.
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