Runtime library app code os device type dependent

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Unformatted text preview: ower than reading a page     Wri<ng to an SSD is complicated   random write to exisKng block: read block, erase block, write back modified block   leads to hard ­drive like performance (300 random writes / s)   sequenKal writes to erased blocks: fast!   SSD ­read like performance (100 ­200 MB/s) 31 May 2012 Disks and File Systems 21 University of Washington SSDs: dealing with erases, writes   Lots of higher ­level strategies can help hide the warts of an SSD   many of these work by virtualizing pages and blocks on the drive (i.e., exposing logical pages, not physical pages, to the rest of the computer)   wear ­leveling: when wriKng, try to spread erases out evenly across physical blocks of of the SSD   Intel promises 100GB/day x 5 years for its SSD drives   log ­structured filesystems: convert random writes within a filesystem to log appends on the SSD   build drives out of arrays of SSDs, add lots of cache 31 May 2012 Disks and File Systems 22 University of Washington SSD cost   Capacity   today, flash SSD costs ~$1.00/GB (down from $2.50 a year ago) 1TB drive costs around $1000 –  1TB hard drive costs around $100   Data on cost trends is a lible sketchy and preliminary     Energy ...
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