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Title
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Analytic models for flash-based SSD performance when subject to trimming
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Author
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Abstract
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| Garbage collection is known to have a profound impact on SSD performance as it strongly influences the write amplification. Another key value that impacts the write amplification is the amount of over-provisioning, which lowers the write amplification at the cost of reducing the user-visible storage capacity. Write amplification occurs as the valid pages that remain on a block selected by garbage collection need to be copied to a free block before an erasure can take place. Some of these valid pages may however belong to a deleted file and therefore copying them is redundant. To avoid copying deleted data, the operating system can issue a Trim command to invalidate pages whenever a file is deleted. Prior analytical studies on the write amplification in SSDs assumed that no trimming takes place. In this paper we generalize a number of mean field models to assess the impact of trimming on the write amplification. Using these models we argue that the write amplification in a (large) system with trimming can be determined by analyzing a system without trimming that uses a larger over-provisioning factor (and modified hot fraction, in case of hot and cold data). Using numerical results we further show that trimming cold data results in a more significant reduction in the write amplification compared to trimming hot data. |
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Language
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English
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Source (journal)
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IEEE ... Symposium on Mass Storage Systems and Technologies : [proceedings]. - Piscataway, NJ
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Source (book)
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Proceedings of 32nd International Conference on Massive Storage Systems and Technology (MSST), Santa Clara, Calif. (US), 2016
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Publication
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New york
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Ieee
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2016
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ISBN
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978-1-4673-9055-2
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978-1-4673-9055-2
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DOI
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10.1109/MSST.2016.7897086
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Volume/pages
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(2016)
, 14 p.
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ISI
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000402384200013
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Full text (Publisher's DOI)
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Full text (open access)
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