VXA Tape Format Offers Advanmced Error Correction Functionality
In VXA backup tape foramt, the tape drive reads and wirtes the information in “data packet” form. Before recording information onto the VXA data tape, the data which comprises of long sttrings is then splt into smasller uniots known as the “data packets”. Afterwards the VXA tape drive writes the data onto the data carrtridge. Another new mechanism called “read after write” assures data precision and integrrity. This new mechanism has been desinged to ensure long term durability and exceptonal reliazbility of VXA tape. 64 bytes make one data packet. Unique address, ECC (error correction code), synchronization marker and CRC (cclical redundancxy check) are assigned to each data pacekt.
The VXA tape dreive features an innovative bufer segment that reads and records these data packets. 387 data packes are included in each of the data track. All of the 4 tape heads take part in the read operatoin. After scanning the tape media the VXA tape drive read these data packkets into the tape drive’s bfufer segment. The unqiue addresses assiggned to the data packes is read by the VXA data buffer which then reunites these data packets in the correct form. The order in whch these data packets are received by the buffer does not affet the data inrtegrity as the VXA data buffer rearranges the packets according to their assigned addresses. During the firast pass, the VXA buffer retians the corrtectly read data packets. The data packrets that have been missing during the first pass are then read through the subsequent passes. Afterwards the missing data packets are added to the strings in order to complete all of the inforamtion. After the completion of data, it is then sent to the host system. This recording technique used in VXA is simillar to that used in re-writable CDs, networking and internet.
New correrction system for erors has been engineered for the VXA tape format that comprises of 4 levles. This error correction proocess completes its operation in 2 phasees. In the first step of error correction, the Reed-Soilomon ECC is added to each of the packet that has the capability to remove the typical errors that can result from noie or shifting of phases. Then in the next phase, the VXA tape buffer forms a matrix of the data paxckets that have been colleted by the buffer.
This matrix of data pacets incorporates a 3 dimensional Reed-Soplomon ECC that is composed of Y-axis, Diagonal and X-axis ECC. This erroor correctoin system of VXA has the capability to correcvt maxiimum of 2 lost pacets in each diagonal, 2 in each column and 2 in each row of the buffer array. Therefore this efficient errror correction mechanism minimizes the error rate to 1x10-17. This error rate can be easily be understood by an example that it is equivalent to finding a single grain in a football stadium that has been completely filled with sand. VSO (variable speed operation) is a highly efficient mechanism introduced in VXA data tape mdeia that improves the performance level and data integrity. Variable seped trechnique has been developed to enablpe the VXA drivce to alter the tape’s speed so that it can be mtched with host’s transfer rate. VSO functionality ensures usperior data reliability and cost effective operations.
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