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|Tape's vanishing act|
Tape replacement is happening now...
18% of organizations have already permanently replaced tape with disk (and that number is rising quickly) 58% would consider permanently replacing tape with disk
Of the 58% who would consider replacing tape libraries, 80% believe they'll do so within 24 months
... and in a big way
50TB to 99TB is the mean capacity migrated to disk by early disk-based backup adopters
26% of disk-based backup adopters have migrated more than 100TB
The majority of users say that 40% of their current tape-based capacity will be migrated to disk three years from now
Source: ESG Research, March 2005
ESG's 3DR concept describes three levels of data protection. 1DR is "data recovery," 2DR is "disaster recovery" and 3DR is "doomsday recovery" (see "Storage Bin: Introducing 3DR," Storage, June 2006)
The 3DR model is built on two basic premises: All recoveries should be from disk, and tape should be reserved for long-term and offsite archival. Let's take a closer look at each of the three DR levels.
1DR: This is the primary data protection tier. In an ideal world, this tier is 100% disk based, although it's likely to be a blend of both disk and tape. Over time, we expect (and advise) organizations to create an all-disk-based 1DR tier and to repurpose existing tape resources for long-term or offsite archival purposes (see "Tape's vanishing act," this page).
The 1DR tier is all about recovery. It's about making sure that the data protection environment meets defined RPOs and RTOs for data over its changing lifecycle. It's also about improving backup performance and reducing management issues. Typical disk targets for this tier include virtual tape libraries (VTLs), "dumb" disk, NAS, content-addressed storage, midrange arrays and possibly even high-end disk systems.
2DR: This disaster recovery tier is also disk based. Its objective is to make a replica of 1DR data and keep it offsite for disaster recovery purposes. This replica of the data could be created using expensive and complex storage system-based, remote-mirroring solutions; less-expensive, host-based replication solutions; or even some type of disk-to-disk-to-disk scenario in which data is backed up to disk (an array, NAS device or VTL) and then moved offsite over the WAN to another disk system.
3DR: While 1DR and 2DR are the disk-based tiers in this scheme, 3DR is tape based. This is the end of the line, so to speak. The idea is to keep a finite amount of tape copies for the worst-case scenario--when your 1DR and 2DR copies are destroyed or otherwise made unavailable.
This was first published in September 2006