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Reliability and Availability

Data reliability and availability increase with Panasas® ActiveStor®  Solution. In NAS systems, adding storage capacity boosts the frequency of drive failures, simply because there are more drives. Panasas uses software-based erasure codes to protect each file individually instead of protecting whole raw storage devices. File-level protection accelerates rebuild times, increasing data availability and reliability with scale.


Erasure-Coded Protection

The Panasas advanced per-file, distributed-erasure-coding software implementation offers two levels of protection. It applies dual-parity erasure-coded protection as it distributes data in each file across storage nodes in the cluster. This protection corrects up to two simultaneous failures, whether drives or whole nodes. The second level of protection handles failures that occur in a portion of a drive, where just a range of blocks within a drive is inaccessible. This allows the ActiveStor appliance to detect and correct sector-level errors and other low-level issues without requiring a full node-level rebuild.

DATA RELIABILITY VOLUME OF REBUILD DATA TIME TO REBUILD DATA EXTENDED FILE SYSTEM AVAILABILITY (EF SA)
Legacy NAS w/ RAID 6 Decreases with scale
  • Substantial amount of data to be rebuilt after disk failure
  • Rebuilds files entire drives, even the portions of them that do not contain user data
  • Higher risk of compounding failures while in degraded mode
  • Rebuild B/W limited by only writing to the “hot spare” drive
  • Rebuilds can take days
  • Rebuild performance  is not scalable
  • File system not available after triple disk failure
  • Complete file system restore likely required
PanFS w/ RAID 6+ Increases with scale
  • Minimal data to rebuilt after disk failure
  • Only repairable files rebuilt in most cases
  • Lower risk of compounding failures while in degraded mode
  • Rebuild B/W scales by utilizing all storage nodes at once
  • Rebuilds only take hours
  • Rebuild performance scales with the system
  • File system is available after triple disk failure
  • PanFS will list the path names of all the affected files

Data Scrubbing

The Panasas PanFS® operating environment performs background scrubbing of all files. It checks to ensure that all levels of data-protection information for each file, such as code parity information, match the data in the file. The vertical parity layer can detect and correct latent “bit rot” errors in the drive media. Data scrubbing helps catch any latent failures early so you can fix them before data loss occurs.


Extended File System Availability

The PanFS storage operating system provides extended file system availability protection for the namespace, directory hierarchy, and file names. In the extremely unlikely event of an unrecoverable failure, the PanFS platform pinpoints affected files and isolates them. With this additional layer of protection, the PanFS solution can usually identify the full path names of affected files. Users enjoy uninterrupted access to all files unaffected by the failure, and the PanFS system logs any affected files for restoration from backup or another source.


Parallel Rebuild

Ensuring data reliability while scale and performance increase requires parallel reconstruction. Because PanFS rebuilds files instead of drives, and stripes files across differing subsets of all the storage nodes that it manages, it rebuilds all files affected by a failure in parallel. The PanFS rebuild is not limited by the performance of a single drive. Rebuild performance scales as linearly as data access performance.

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