Thank you for purchasing through links and ads on this site.
OWC / MacSales.com...
diglloyd Deal Finder...
Buy other stuff at Amazon.com...
Rigorously lab tested and OWC certified.

SAVE $900 Apple 15.4" MacBook Pro with To…

SAVE $450 Apple 13.3" MacBook Pro Laptop…
SAVE $900 Apple 15.4" MacBook Pro with To…
SAVE $900 Apple 15.4" MacBook Pro with To…
SAVE $200 Sigma sd Quattro H Mirrorless
SAVE $500 Sony a7R II Mirrorless
SAVE $300 Sony 28-70mm f/3.5-5.6 Alpha a7…
SAVE $200 Sony 28-70mm f/3.5-5.6 Alpha a7…
SAVE $200 Sony a7 Mirrorless
SAVE $50 Sony DSC-RX100 V with Free Acce…
SAVE $350 Sony a6300 Mirrorless with 16-5…
SAVE $100 Sony a5000 Mirrorless with 16-5…
SAVE $100 Sony a6000 Mirrorless Body (Gra…
SAVE $150 Sony a6000 Mirrorless with 16-5…
SAVE $100 Nikon D3300 DSLR with 18-55mm
SAVE $200 Olympus OM-D E-M1 Mark II Mirro…
SAVE $200 Panasonic 42.5mm f/1.2 Leica DG…
SAVE $300 Olympus OM-D E-M5 Mark II Mirro…
SAVE $150 Fujifilm X-A10 Mirrorless with…
SAVE $750 Fujifilm X-T1 Mirrorless
SAVE $1151 Zeiss 15mm f/2.8 Distagon T* ZE
SAVE $500 Canon EOS 6D DSLR Body with Sto…
SAVE $700 Canon EOS 5D Mark III DSLR
SKU DRSP1000B
SAVE $100 Sony 35mm f/2.8 Sonnar T* FE ZA
SAVE $750 Fujifilm X-T1 Mirrorless
SAVE $200 Sigma sd Quattro Mirrorless
SAVE $200 Sigma 30mm f/1.4 sd Quattro Mir…
SAVE $250 Sigma dp0 Quattro with LVF-01 L…
DZ SAVE $40 Lowepro Passport Sling Camer…
DZ SAVE $160 teenage engineering Pocket O…
DZ SAVE $250 Amimon Falcore Racing Drone…
DZ SAVE $50 Hdrsoft Photomatix Pro 6.0 (…
DZ SAVE $40 Lowepro Passport Sling Camer…
DZ SAVE $80 Sennheiser HANDMIC DI… 9 min
DZ SAVE $160 ikan Mylo MB4 Mini Bi-Color…
View all 36 deals…

Promise Pegasus J4 — SSD Speed (Incompressible)

Last updated 2013-07-03 - Send Feedback
Related: Storage, SSD, storage, Thunderbolt

Tested on the 2.7 GHz MacBook Pro with Retina display, which has a Thunderbolt connector.

This test is for incompressible data.

Update: see issues.

What is incompressible data ?

Some types of data cannot be compressed: ZIP files, videos, image files (JPEG, PNG, GIF, compressed TIF, some PSD and PSB files), compressed audio files (MP3, etc), some (but not all) digital camera raw format files—such file types are already compressed internally and cannot be compressed any smaller.

Read and write speed with incompressible data

The Sandforce controller in many SSDs including the OWC Mercury Elite Pro 6G SSD drops in write performance with incompressible data.

Read performance on incompressible data is generally unaffected, and since most scenarios see reads dominate, the write speed is often not terribly important so long as it is still reasonably fast.

Other factors

While one can wish that this write speed were unaffected by incompressible data, it is an adaptive behavior designed to extend the life of the SSD. Also, there are other behaviors that can cause slowdowns, and some brands start having trouble with increased capacity usage. So one should not ignore the context of real world usage.

Sustained transfer speed — incompressible data

This test is a worst-case: a pure random stream of data without repetition. Real-world data is usually not so unforgiving.

While the random data generation in the test runs in its own computing thread, there can be a small performance 'hit' as speeds increases, adding 10% to the 3 and 4 drive cases is probably realistic for real-world where there is no compute load.

Detailed conclusions follow below. In brief:

  • For most every real-world case, two SSDs provides outstanding performance. Using 3 or 4 SSDs is unlikely to help for anything but rare situations.
  • Critical performance environments where performance variation must be held to a tight level should stripe four SSDs. Otherwise, no particular benefit other than capacity.
  • Either two or three SSDs provide read performance on par with four SSDs.
  • A single SSD is still very fast! But the sweet spot for users looking for high performance at reasonable cost is a dual-SSD RAID-0 stripe.

Tested with diglloydTools DiskTester using the fill-volume test.

RAID-0 stripes of 2/3/4 SSDs + single SSD
(Data from diglloydTools DiskTester data graphed from fill-volume test)

Analysis

  • With two or three or four SSDs striped, the read speed is essentially identical. Hence two SSDs are enough to deliver maximum speed for reads.
  • Two SSDs striped: write speed for incompressible data is about the same as for writing highly compressible data with a single SSD.
  • Three SSDs striped: write speed variation is at or above the average speed for two SSDs striped.
  • Four SSDs striped: nice “tight” read/write performance at ~800MB/sec.
  • Four SSDs striped: the Thunderbolt bus is still the limiting factor (or very close to it); performance has no practical difference from the compressible-data case.
Read speed for compressible vs incompressible data
Write speed for compressible vs incompressible data
RAID-0 stripes of 2/3/4 SSDs + single SSD for incompressible data
(diglloydTools DiskTester data graphed from fill-volume test)
SSD Upgrade for MacBook Pro Retina
Internal SSD Wishlist…
B&H Deal ZoneDeals by Brand/Category/Savings
Deals expire in 8 hours unless noted. Certain deals may last longer.
$2099 SAVE $700 = 25.0% Canon EOS 5D Mark III DSLR in Cameras: DSLR
$798 SAVE $200 = 20.0% Sony a7 Mirrorless in Cameras: Mirrorless
$2398 SAVE $500 = 17.0% Sony a7R II Mirrorless in Cameras: Mirrorless
$1799 SAVE $1151 = 39.0% Zeiss 15mm f/2.8 Distagon T* ZE in Lenses: DSLR

diglloyd.com | Terms of Use | PRIVACY POLICY
Contact | About Lloyd Chambers | Consulting | Photo Tours
Mailing Lists | RSS Feeds | Twitter
Copyright © 2008-2017 diglloyd Inc, all rights reserved.
Display info: __RETINA_INFO_STATUS__