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...
$30 $15
SAVE $15

$2998 $2498
SAVE $500

$1199 $920
SAVE $279

$1999 $1599
SAVE $400

$2799 $2399
SAVE $400

$89 $59
SAVE $30

$400 $280
SAVE $120

$1798 $1598
SAVE $200

$3297 $2797
SAVE $500

$3397 $2797
SAVE $600

$150 $90
SAVE $60

$1398 $898
SAVE $500

$3698 $2998
SAVE $700

$1799 $1329
SAVE $470

$1999 $1199
SAVE $800

$2299 $1599
SAVE $700

$2399 $2049
SAVE $350

$2799 $1899
SAVE $900

$997 $897
SAVE $100

$2099 $1699
SAVE $400

$1999 $1369
SAVE $630

$1349 $949
SAVE $400

$4499 $3999
SAVE $500

$329 $329
SAVE $0

$1499 $1029
SAVE $470

$1499 $1289
SAVE $210

$2199 $1999
SAVE $200

$3399 $2199
SAVE $1200

OWC Thunderbolt 3 Dock
Ideal for any Mac with Thunderbolt 3


Dual Thunderbolt 3 ports
USB 3 • USB-C
Gigabit Ethernet
5K and 4K display support plus Mini Display Port
Analog sound in/out and Optical sound out

Works on any Mac with Thunderbolt 3

RAID 1 Mirroring

Last updated 2014-01-10 - Send Feedback
Related: backup, fault tolerance, RAID, RAID-1, storage

A RAID mirror* replicates data onto two or more disk partitions (onto two or more hard drives); this is a form of fault tolerance.

When a drive fails, operation continues seamlessly with the other drive: no data is lost. The failed drive can be replaced, and the mirror can rebuild, automatically (this is one oddball way to backup: swap one of the drives in the mirror with a blank one).

RAID-1 mirror
2 or more drives,
one volume, one icon

A RAID mirror is a single volume that looks and behaves exactly like a single “drive” (volume): one icon on the desktop. That is the beauty of a mirror: there is absolutely no difference in usage as compared to a single drive/volume, yet failure of one drive maintains all data and functionality.

Typically a RAID-1 mirror consists of the entire capacity of all the drives in the mirror set but it is possible to mirror partitions across drives.

* The term “mirror” is historical and apparently chosen by someone who never looked into one (hint: try to read printed matter in a mirror). A better term would have been “RAID Replica”.

Fast and cost effective way to backup!

2 or more mirrors

If there are N drives (partitions) in the mirror, then N-1 of them can fail with no loss of data. The most common setup is with N = 2 drives.

A RAID-1 mirror can be created in software with two or more independent drives, or via hardware such as a dual-drive unit like the OWC Mercury Elite Pro Dual.

Mirroring generally runs at the speed of a single drive or a bit slower for writes (all drives can be written simultaneously, but there is some overhead). A mirror can offer higher read speed, but not necessarily.

Backup is still required

Mirroring is not a backup system, it’s a fault tolerance system. For example, a RAID mirror does not protect against theft or natural hazards.

A consistent backup strategy is critical, even with mirroring: Acts of Dog can occur (fire, hurricane, lighting bolt, etc).

Apple iMac 5K Speed Demon
$3849
$3499

It rocks! What Lloyd uses every day, best upgrade in many years!

SMART MOVES:
• Add 128GB or 64GB memory
fast SSD storage
Thunderbolt storage

√ B&H Photo PAYS THE SALES TAX FOR YOU More info...

Creating a software RAID-1 mirror

See the RAID-1 how-to page.

Creating a RAID-1 mirror with DiskUtility
OWC Thunderblade Thunderbolt 3 SSD
Gen 2!

Blazing fast, 1TB, 2TB, 4TB, 8TB.

Lloyd’s all-time favorite SSD!

√ No more slow and noisy hard drives!
OWC
USB-C Travel Dock

Fast charging with up to 100W!

HDMI, SD card reader,
USB-C port, 2 USB Type-A ports
Built-in cable self-stores neatly.
See also OWC 14-port Thunderbolt 3 Dock"

Deals Updated Daily at B&H Photo
View all handpicked deals...

Pelican 3rd-Generation 1910B LED Flashlight (Black)
$30 $15
SAVE $15

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__