author	 = {Niklas Behrmann},
	title	 = {{Support for external data transformation in ZFS}},
	advisors	 = {Michael Kuhn and Anna Fuchs},
	year	 = {2017},
	month	 = {04},
	school	 = {Universität Hamburg},
	howpublished	 = {{Online \url{}}},
	type	 = {Master's Thesis},
	abstract	 = {While computational power of high-performance computing systems doubled every two years over the last 50 years as predicted by Moore’s law, the same was not true for storage speed and capacity. Compression has become a useful technique to bridge the increasing performance and scalability gap between computation and Input/Output (I/O). For that reason some local filesystems like ZFS support transparent compression of data. For parallel distributed filesystems like Lustre this approach does not exist. Lustre is frequently used in supercomputers. The Intel Parallel Computing Centers (IPCC) for Lustre filesystem project is aiming for compression support in Lustre at multiple levels. The IPCC are universities, institutions, and labs. Their primary focus is to modernize applications to increase parallelism and scalability. A prior thesis started the implementation of online compression with the compression algorithm LZ4 in Lustre. The focus of this implementation was to increase throughput performance. The data is compressed on clientside and send compressed to the server. However the compression leads potentially to a bad read performance. This problem might be solved through modifying the ZFS filesystem which is utilized by Lustre servers as a backend filesystem. ZFS already has a compression functionality integrated which provides good read performance for compressed data. The idea is to make use of this and store the Lustre’s data in ZFS as if it was compressed by ZFS. Therefore a new interface that takes the necessary information has to be created. Implementing this is the purpose of this thesis. The goal is to enable the Lustre compression to save space on disk and most importantly fix the bad read performance. Throughout this thesis the necessary modifications to ZFS are described. The main task is to provide information to ZFS about the compressed size and the uncompressed size of the data. Afterwards a possible implementation of the specified feature is presented. First tests indicate that data which is compressed by Lustre can be read efficiently by ZFS if provided with the necessary metadata.},