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 2018 Mac mini up to 64GB
GET THE BEST DEALS
Top deals pages updated daily for Sony, Nikon, Canon, Apple, many more!
Instant rebates, Black Friday deals, etc

RAID 1 Mirroring

Last updated 2014-01-10 - Send Feedback
Related: fault tolerance, RAID, 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”.

Up to 1527MB/s sustained performance

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).

Deals Updated Daily at B&H Photo
View BEST Deals Right Now

Creating a software RAID-1 mirror

See the RAID-1 how-to page.

Creating a RAID-1 mirror with DiskUtility
Deals Updated Daily at B&H Photo
View BEST Deals Right Now
B&H Deal ZoneDeals by Brand/Category/Savings
Deals expire in 169 min unless noted. Certain deals may last longer.
$797 SAVE $350 = 30.0% $59 FREE ITEMS Nikon D5600 DSLR with 18-55mm and 70-300mm Lenses in Cameras: DSLR
$1099 SAVE $300 = 21.0% $249 FREE ITEMS Sigma 70-200mm f/2.8 EX DG APO OS HSM in Lenses: DSLR
$3498 SAVE $1000 = 22.0% Sony a9 Mirrorless in Cameras: Mirrorless

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__