Device mapper

Abstract: Data security has come to be of utmost importance in the recent times. Several encrypting file systems have been designed to solve the problem of providing data security in a secure and transparent manner. TransCrypt is such an encrypting file system, which is implemented in kernel space, has an advanced key management scheme and is designed to be deployable in an enterprise scenario. It uses per-file cryptographic keys for flexible sharing and does not include even the superuser in its trust model. Earlier, TransCrypt was implemented on the Linux kernel (version 2.6). In the implementation, several modifications were made to the existing kernel to embed the TransCrypt functionality. Such modifications also changed the file I/O behaviour in the kernel, in order to add a cryptographic layer to perform encryption and decryption on the file data. The kernel thus modified had several limitations with respect to functionality, maintainability and performance. In this thesis, we propose a new cryptographic layer for the TransCrypt file system. This layer is implemented as a kernel module and does not modify any existing kernel code. The module uses the device-mapper infrastructure provided by the Linux kernel. The new layer addresses several limitations of the earlier implementation, and is robust and stable. Performance gains of over 90% were observed in read and write operations on large files with the new implementation. The design and implementation details of the new cryptographic layer and performance measurements are discussed in this work.

Abstract: The invention provides an input/output (IO) cache operation method and an IO cache operation system based on a device mapper (DM) layer of a Linux system. The method is implemented by a Linux kernel and comprises a reading process and a writing process. High-speed storage equipment is added as a cache of physical equipment, and the common data is put into the high-speed storage equipment, so that the performance of a disk accessed by a user is improved.

Abstract: The invention provides a cache system based on a nonvolatile memory and a software RAID. The cache system is characterized in that the cache system is a novel storage system architecture by fusing a nonvolatile memory Apache Pass, a software RAID, and a Device Mapper driving module Buaacache. According to the invention, the software RAID is managed by means of the Device Mapper mechanism of the Linux, a high-speed device Apache Pass serves as the Cache of a low-speed RAID, and therefore a two-stage cache system is constructed. The Persistent Memory is characterized in that after the Persistent Memory is powered off, medium data is not lost, and the read-write performance is excellent. According to the invention, the Persistent Memory is selected as the cache of the software RAID, under the condition that the cost is far lower than that of a hardware RAID, the read-write performance of the software RAID approaches even exceeds the hardware RAID.

Abstract: The invention relates to a distributed type network caching method based on a Device Mapper. The distributed type network caching method based on the Device Mapper is characterized in that when a plurality of client sides concurrently access a shared storage server, the client sides utilizes a local disk and disks of other client sides in a local area network (LAN) as caching of the storage server, when access requests of the client sides hit caching of the local disk, the access requests of the client sides are transmitted to the local disk to be processed; when the access requests of the client sides hit caching of the disks of other client sides, the access requests of the client sides are transmitted to the disks of other client sides; and when caching of all the client sides is not hit, the access requests of the client sides are transmitted to a disk of the server, therefore loads and network bandwidth consumption of the storage server are reduced, and the using rate and the request access speed of the disks of the client sides are enhanced. The distributed type network caching method based on the Device Mapper can be used for a high concurrency network storage system.