Thank you for purchasing through links and ads on this site.
OWC / MacSales.com...
diglloyd Deal Finder...
Buy other stuff at Amazon.com...
Upgrade the memory of your 2019 iMac up to 128GB
Handpicked deals...
$3099 $1999
SAVE $1100

$3199 $2099
SAVE $1100

$4199 $2899
SAVE $1300

$2299 $1499
SAVE $800

$3399 $2399
SAVE $1000

$3198 $2198
SAVE $1000

$779 $679
SAVE $100

$5499 $4999
SAVE $500

$1799 $1299
SAVE $500

$719 $299
SAVE $420

$1799 $1299
SAVE $500

$795 $344
SAVE $451

$1997 $897
SAVE $1100

$1100 $900
SAVE $200

$348 $278
SAVE $70

$348 $278
SAVE $70

$3099 $1999
SAVE $1100

$2099 $1799
SAVE $300

$699 $499
SAVE $200

$1699 $1299
SAVE $400

$2999 $2599
SAVE $400

$1699 $1443
SAVE $256

$2798 $2498
SAVE $300

$2399 $2199
SAVE $200

$3798 $1898
SAVE $1900

$2840 $2498
SAVE $342

$2497 $1897
SAVE $600

$2498 $1798
SAVE $700

$3297 $1997
SAVE $1300

$2798 $2498
SAVE $300

$2998 $2498
SAVE $500

$1398 $1198
SAVE $200

$898 $798
SAVE $100

$1299 $939
SAVE $360

$4499 $2699
SAVE $1800

$4999 $4599
SAVE $400

$2199 $1999
SAVE $200

$2799 $2349
SAVE $450

$3099 $1999
SAVE $1100

$2016 $1298
SAVE $718

$249 $149
SAVE $100

$2844 $2297
SAVE $547

$1199 $1099
SAVE $100

$2019 $1399
SAVE $620

$999 $949
SAVE $50

New Mac Pro?

Consult with Lloyd today—


System configuration for CPU, GPU, memory, SSD, backup, RAID, optimizing performance, workflow.
For YOUR optimal workflow

Avoid costly mistakes in throwing money at the problem for less performance and/or buying the wrong machine for your own needs!

Promise Pegasus J4 — SSD Speed (Fast Hard Drives)

Last updated 2013-07-05 - Send Feedback
Related: diglloydTools, hard drive, RAID, RAID-0, SSD, storage, Thunderbolt

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

Update: see issues.

Sustained transfer speed

Four Hitachi Travelstar Z7K500 500GB 7200 RPM laptop hard drives were installed in the Pegasus J4 and configured as a 2TB RAID-0 stripe.

Tested individually, these drives are good for ~128 MB/sec. In a 4-way stripe, this scales almost perfectly to a speed of 404 MB/sec average across the capacity, with peak speeds hitting ~518 MB/sec. Using two or three drives striped scales similarly.

Note: this is sustained transfer speed only; some types of jobs will greatly benefit from the low latency of SSDs (no rotational latency, no seek time), in addition to the higher SSD speed.

Observe that a mirrored pair of drives (lowest lines) offers performance slightly better than a single drive for reads as the capacity fills up; most likely this is due to some interleaving (interleaved striped reads are feasible in a RAID-1 mirror). In theory, reads in a mirror should be as fast as a stripe, but the author has never observed this benefit in practice.

Speeds shown in the bar graph below are average speeds across the entire capacity.

Tested with diglloydTools DiskTester using the fill-volume test.

Hard drive performance in Pegasus J4, single drive, mirror, RAID-0 striping
(Data from diglloydTools DiskTester data graphed from fill-volume test)

Speed across the volume capacity

Speed declines across the capacity of hard drives. By using RAID-0 striping, higher peak speeds are obtained, but an added benefit is that higher average speed is maintained for the same capacity utilization

Observe that even when filled to capacity (slowest possible case), a 2-drive RAID-0 stripe is substantially faster than a single drive when empty (at its peak speed).

Hard drive performance in Pegasus J4, single drive, mirror, RAID-0 striping
(Data from diglloydTools DiskTester data graphed from fill-volume test)
Save Big $$$$ on Memory for 2019 Mac Pro

Up to 65% better pricing than Apple

Lloyd recommends 32GB RDIMMS for most users.



MacPerformanceGuide.com
View all handpicked deals...

Canon EOS 5D Mark IV DSLR Camera with Canon Log and Accessory Kit
$3199 $2099
SAVE $1100

diglloyd.com | Terms of Use | PRIVACY POLICY
Contact | About Lloyd Chambers | Consulting | Photo Tours
Mailing Lists | RSS Feeds | Twitter
Copyright © 2019 diglloyd Inc, all rights reserved.
Display info: __RETINA_INFO_STATUS__