VXL thin clients use Solid State drives based on NAND flash technology as internal storage drives. These are configured for standard thin client usage scenarios where, during the normal course of operation, data is NOT written to the system's internal storage drive. The emphasis is on robustness. By not allowing the system storage to be written to, thin clients are not susceptible to security issues such as viruses and malware. Further, this will eliminate wear on the SSDs, significantly protecting and extending product life. The primary purpose of the thin client SSD is to accommodate the Operating System, OS updates, user profiles and any applications that need to run locally.
VXL thin clients use industry standard SSDs which undergo rigorous approval tests prior to qualification.
VXL Windows Embedded operating system includes Write Filter mechanisms such as EWF, FBWF or UWF as a standard feature. These write filters are managed by a tool is known as Write Filter manager.
IT Administrators can enable or disable the write filter using this tool.
Write Filter enable
By default, the Write filter is enabled when the thin client leaves the factory. Enabling Write filter prevents write operations to the system SSD by caching writes to a RAM overlay created within the system RAM. Any data written to this volatile RAM is lost when the system is rebooted.
Write Filter disable
IT Administrators can, if they wish, disable the Write filter in order to make updates and changes to the system image. It is imperative that the write filter is enabled again once the update is completed.
In case the write filter is left disabled by oversight, a warning message appears on the System tray.
Page File is a feature provided by the Windows operating system that allows a part of the SSD to be used as an extension of RAM in order to support more simultaneous processes than possible with the available RAM. This process causes huge writes to the SSD that would normally be directed to the RAM. Enabling the Windows Page File on a thin client will lead to premature SSD wear resulting in degradation in performance and life of the device.
Page File is turned OFF by default on all Windows based VXL thin clients and it should NEVER be turned on for the reasons cited above.
Implications of Flash usage on Warranty
VXL relies on the SSD manufacturer’s warranty and extrapolates the same to cover the thin client product range as described below.
SSD components used in the VXL thin clients are covered by either of the following, whichever occurs earlier:
- Three year limited warranty or
- The day the SSD exceeds the wear limit specifications of the SSD, as indicated by the reading of the Average program / Erase counts using the SMART software.
Non Thin Client usage
It is important to bear in mind that the SSDs, can withstand only a limited number of write cycles, unlike HDDs. This is an inherent characteristic of the NAND flash technology, which form the basis for SSD designs.
Therefore, Use cases that necessitate large amounts of data to be routinely written to the SSD, require a thorough study of the work load and the associated effect on the SSD wear and useful life. It is observed that the size and frequency of writes also have a bearing on the quantum of wear of SSDs. SSD technology is evolving, with periodic announcements of new techniques being deployed to essentially minimize frequent writes to the NAND flash cells within the SSD. These techniques involve aggregating frequent host writes into a local RAM till a predetermined size is attained prior to writing to the NAND flash. As a result of such techniques, newer generation SSDs appear less susceptible to wear, under conditions of frequent writes. Specification for Endurance provides a rough estimate of the total number of writes an SSD can withstand during its life-time.
VXL Pre-Sales support personnel, will are available to assist you with this exercise. The strategy may involve the following actions.
- Capturing the write pattern over a period of time
- Eliminating unnecessary writes to the SSD
- Redirecting non critical writes to a RAM disk
- Providing larger SSDs so that wear get distributed over larger no of cells
- Short listing suitable SSDs
- Conducting experiments simulating the typical field conditions