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The ADvanced Systems Laboratory (ADSL)
Overview
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Semantically-Smart Disk Systems
One rich off-shoot of the gray-box work occurred when we had the following
insight. The disk and RAID industry, for years, had been hampered for years by
limited information: at the block level, all a device sees are reads and
writes, with no knowledge as to the contents of each block, its importance,
and other relevant characteristics. If a ``dumb'' disk could just know more
about how such blocks are utilized, it could implement a surprising range of
features to improve performance and reliability of the I/O system.
As our work demonstrates, gray-box techniques enable such knowledge. By
assuming certain details about the client of the disk (e.g., that it is a file
system of a particular type), a semantically-smart disk can learn how it
is being used and thus implement features previously unattainable at block
level.
- Semantically-Smart Disk Systems (FAST '03)
The original paper, which introduces the idea,
and shows its benefits through three case studies.
- Improving Storage System Availability with D-GRAID (FAST
'04). We show how knowledge of files and directories can lead to
novel new approaches to data layout in RAIDs, which can greatly
improve availability of the file system by exploiting such
knowledge.
- X-RAY: A Non-Invasive Exclusive Caching Mechanism for RAIDs
(ISCA '04). We show how a RAID layer can
determine what is likely cached in the OS above it, and thus avoid redundant
caching, to improve performance.
- Life or Death at Block Level (OSDI '04)
Probably one of our deepest papers upon this
topic, we show how to determine whether a block is live or dead, and
exploiting such knowledge to build interesting new functionality such as a
secure deletion facility, all at block level.
- A Logic of File Systems (FAST '05)
A formal framework to reason about semantic
disks as well as file systems that arose from our empirical work, as we
realized the need for a conceptual theory underpinning our previously
heuristic approaches.
- Database-Aware Semantically-Smart Storage (FAST '05)
A final paper on the topic that highlighted
that smarter disk systems could also be realized underneath database
management systems (not just file systems), and that similar performance
benefits could be achieved.
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