5/30/2023 0 Comments Namechanger windows![]() ![]() Otherwise, the filter cannot attach to SCM volumes. Filters must explicitly indicate if they support direct access storage (by setting the FLTFL_REGISTRATION_SUPPORT_DAX_VOLUME bit in their registration structure Flags field). Some file system filter drivers, notably data transformation filters (encryption/compression/HSM), may be impacted by these changes. Directory Change Notification occurs at memory mapping time.Modification Time and USN Journal semantics are altered slightly (“last update” is the date of memory mapping).No mirrored or parity support (Storage Spaces or Dynamic Volumes).ReFS: no integrity streams, no cluster bands, no block cloning.NTFS: no encryption, compression or TxF (transaction) support.Potentially different types of storage failure.There are some behavior changes with the introduction of SCM in SAS Mode as well: Memory mapping of the file directly maps the SCM memory into the address space, whether it is an application or the Cache Manager. The key benefit for applications using file systems that support the DAS Mode interface is it provides zero copy access. It is supported in Windows 1607 and later by the NTFS and ReFS file systems. This provides perfect application compatibility, but requires I/O operations to traverse (a slightly optimized path through) the Windows storage stack.ĭAS Mode is much more interesting. In Block Mode, SCM devices appear as “ordinary” storage volumes and thus maintain all existing storage semantics. In Windows, the mode is chosen when the SCM device is formatted. SCM devices operate in one of two modes: Block Mode, or Direct Access Storage (DAS) Mode. A Storage Class Memory bus driver (scmbus.sys).For those interested in the device driver aspects of this new technology, there are two new drivers: Support for these persistent memory devices has been present in Linux for various file systems and is now supported in Windows 10. (courtesy of Viking Technology and used with permission) These NVRAM based devices use normal memory slots, but provide persistent storage, which can be used by a file system in order to obviate the need to do any RAM-based caching, due to the performance of the device itself. Direct Access Memory Device SupportĪs of Version 1607, Windows 10 (and Server 2016) have included support for persistent memory storage devices. If you still have a legacy file system filter driver, you’ll almost certainly want to be aware of these changes so you can accommodate them as you migrate to the mini-filter model. While many of these changes will impact file system related drivers including mini-filters, some may impact other drivers as well. ![]() The process we used to identify these changes was a systematic comparison of the header files (ntifs.h, ntddk.h, wdm.h, and fltkd.h), followed by some select careful observation of a running RS1 system. ![]() There have been additional changes since then, but these changes remain significant, and are still a surprise to both experienced and newer Windows devs. In this article, we review several significant changes that were first introduced in Windows 10 Anniversary Update, Version 1607 (build 14393.0). Throughout its many versions, Windows 10 continues to evolve. Last reviewed and updated: 10 August 2020 ![]()
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