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Must-have expansion for 2017 iMac/ MacBook Pro
Thunderbolt 3 • USB 3 • USB-C • Gigabit Ethernet • Dual Thunderbolt 3 Ports
4K Support • Mini Display Port • Analog sound in/out • Optical sound out
Thunderbay Mini with SSDs: Incompressible Data
Related: Other World Computing, OWC Thunderbay, RAID, SSD, storage, Thunderbay 4 Mini, Thunderbolt, video
To increase the lifespan of the flash memory, Sandforce-based SSDs compress data.
Data compression in an SSD reduces write performance when the data is incompressible (JPG, compressed PSD or TIF, most video, encrypted data, etc).
Many other SSDs do not compress data, but also require TRIM (not needed for Sandforce SSDs). It’s a total performance picture that must be assessed: performance under one’s own actual working conditions along with longevity.
In MPG’s multi-year experience with OWC SSDs (Sandforce-based), real-world performance has been excellent (e.g. Photoshop), and lifespan has never been a concern.
Worse case performance: incompressible data
disktester fill-volume --xfer 128M --pattern randomblock
The graph below shows performance with RAID-0, RAID-5 and single SSD for highly compressible data (zeroes) vs worst-case incompressible random data.
As can be seen, incompressible data takes a substantial toll on write performance, but has negligible effect on read performance. See the red bars for each.
Since many types of data are written once and read many times, the impaired write performance is of no consequence. Moreove, real world tasks can shine even when there is heavy write activity (see the Photoshop diglloydHuge results).
See also the results with the OWC 960GB Mercury Electra 6G SSD, which is much faster.
Toggle compare single SSD vs RAID-0 vs RAID-5.