Tunable Reliability
PerfectBits™ Integrity


Cleversafe's reliability features guarantee that information is accurate and available. RAID, invented decades ago, was simply not designed to store data at the petabyte and beyond level. Cleversafe's Dispersed Storage approach addresses the shortcomings of RAID, guaranteeing bit-perfect storage and delivery.

How? Leveraging an information dispersal approach that has been used successfully in the telecommunications industry, Cleversafe's Dispersed Storage technology provides tunable reliability. Our approach uses Reed Solomon coding — erasure codes, a type of forward error correction — to transform a set of k symbols into a set of n symbols to create redundancy before splitting and storing the symbols in a number of different storage nodes in such a way that only a subset of n symbols are needed to recover the original data.

  • n is the total number of slices created
  • k is the threshold of slices needed to bit-perfectly recreate data

Typically, the solution is deployed across three or more data centers, and based on the number of data centers, a k of n configuration is determined.

Scenario One

Suppose you have four data centers. Perhaps an 8 of 12 configuration would be used, with three Slicestor appliances across each data center. Since only eight slices are required to bit-perfectly recreate data, an entire data center could be unavailable plus one appliance failure, and data would still be seamlessly available.

This would be achieved with only 50% storage expansion over the original data size.

Scenario Two

With four data centers, perhaps a 10 of 16 configuration would be used, with four Slicestor appliances across each data center. You could tolerate an entire data center failure plus two Slicestor appliance failures, and still access data.

This would be achieved with only 60% storage expansion over the original data size.


Bit-Perfect Storage and Delivery

Cleversafe's PerfectBits™ integrity guarantees bit-perfect storage and delivery. Here's how.

Cleversafe has two levels of integrity checks within PerfectBits integrity:

  • Integrity checks on each individual slice
  • Integrity check on data file which is confirmed prior to delivery

Integrity Check on All Slices and Files

Bit-Perfect Storage and Delivery with PerfectBits from Cleversafe

These ensure when data is requested, you're guaranteed bit-perfect delivery.

Continuous Error Correction

PerfectBits integrity also employs an intelligent background process that scans slices, checking their integrity values.

  • If a slice is determined to be corrupted—meaning the integrity check value is invalid— the Slicestor appliance starts the distributed rebuilder technology to replace the slice with a valid slice.
  • If the slice is missing, the distributed rebuilder technology recreates a valid slice.
  • Integrity checks on each individual slice
  • Integrity check on data file which is confirmed prior to delivery

Cleversafe Slicestor Integrity Check and Continuous Error Correction

Continuous error correction also increases system availability because it is not waiting for data to be read to detect errors. This is crucial with long-term archives and massive digital stores where information isn't as frequently read.

Send Hackers Packing

PerfectBits integrity also ensures data cannot be modified without authorization—and detects malicious threats.

Suppose a hacker manages to get into a Slicestor appliance and starts changing bits of a slice. If the integrity check value is changed, the background process will detect it and a valid replacement slice will be generated.

But what if the hacker changes bits, but not the integrity check value? The system will think the slice is valid for file recreation, but once all the slices are returned and the data integrity check value is checked, it will be invalid. The system will detect if just one bit is changed. This means PerfectBits integrity can guarantee that data is bit-perfect. Information in. Same information out.

Additional Resources