FlexRAID

FlexRAID is a family of storage data protection and recovery solutions.
Overview
the architectural approaches of the RAID software familty is for achieving flexibility and energy efficiency. The program was developed upon the approach that system efficiency is achieved by minimizing data loss. Minimizing data loss would be done by limiting losses beyond the tolerance level of the failed units. The software further focuses on minimizing energy consumption by localizing data and spinning down disks not being accessed.
FlexRAID,when RAID (RAID-F) combined Transparent RAID (tRAID), features N+1 and N+X parity data protection through various RAID engines. All of the engines have their own nomenclature in the form of Tx, where T stands for Tolerance and x represents the tolerance level. The most acclaimed of them all is the Tx engine providing RAID∞ (infinity) data protection and recovery.
FlexRAID solutions aims to be easier to implement and deploy and supports a wide veriety of disks compatibilities. Flexraid allows for regaining complete control of source disks and the data those disks contain at any given time.
Transparent RAID (tRAID)
Transparent RAID keeps disks entirely independent while providing parity protection for recovery in case of disk failure.
It works transparently underneath the File System.
Features:
* Live Data Reconstruction on disk failure or read errors
* Online Data Expansion
* Online Data Restoration
* RAID Contraction
* Background Scrubbing
RAID over File System (RAID-F)
RAID over File System (RAID-F) with its acclaimed Snapshot RAID feature works above any file system and provides protection to actual file data rather than to storage blocks.
RAID-F does not mandate its own File System. Rather, it supports whatever File System the end-user chooses to use. A light-weight File System transparently overlays the native File System chosen by the end-user. The overlay leaves the file management aspects to the underlying File System but records and manages additional File System metadata for its functions.
Snapshot RAID
The Snapshot aspect of RAID-F provides the following benefits:
Motivations:
* Most user data is static or semi-static
** Only data such as database data, operating system data, and certain non-static critical application data really require real-time synchronization
** It is very inefficient to monitor and synchronize data that is infrequently changing
** More than 90% of the data in most RAID scenarios is static or semi-static data. As such, it can be more efficient to mirror the 10% that is very dynamic and protect the 90% that is semi-static through Snapshot RAID
* Movies, music, photos, documents, TV recordings, downloads, backups, etc. are all types of static and semi-static data best suited to be protected through Snapshot RAID
Features:
* Data checksum and bit rot detection
* Can protect local disk data
* Can protect data off removable media
* Can protect data visible over a network and the internet
* Any data that is visible to the OS can be added to the array (e.g., loading NTFS drives in Linux or Ext3 drives in Windows)
::Therefore, if a supported operating system can load a device and "see" its data content, then it is possible to add that data to the RAID array.
* Offline protection (i.e., not running all the time taking valuable CPU and I/O resources)
* RAID update operations can be scheduled or run manually at one's convenience
* Popular on both standard Windows and Linux installs as well as canned systems such as AMAHI, OpenMediaVault, Windows Home Server platform (WHS)
* Data that needs real-time synchronization should not be included in a Snapshot RAID but should be protected under either RT RAID or under Transparent RAID
RT RAID
Real-Time RAID over File System (RT RAID) is currently an experimental feature of RAID-F. It is stable for some deployments but has issues on heavily fragmented file systems.
Just like Snapshot RAID, it works above the File System but provides real-time parity synchronization.
Terms
UoR
Unit of Risk:
In a traditional RAID sense, a UoR is a physical hard disk. In FlexRAID, a UoR is typically a physical hard disk, but it can also be other data sources.
A Unit of Risk (UoR) is any unit whose failure can be recovered from. That unit can be a file, a folder, a partition, a drive, a media disc, a standard RAID volume, a network share, a LUN, or a set or combination of them.
Put another way, a UoR is anything that contains data that one wants failure protection from.
DRU
Data Risk Unit:
A DRU is a UoR that contains user data.
PPU
Parity Protection Unit:
A PPU is a UoR that contains parity data computed from the DRU(s).

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