blakerwry said:
hmm.. dedicated parity disk.. byte level vs block striping.. that would be called RAID 3...
gee... how many people use RAID 3?
"SynchRAID is based on the same principle as the original RAID 3 bit-wise stripe approach, a technology well known for its advantages in video and large file streaming applications"
"In particular, the architecture is capable or striping directly onto a disk array at word level without the need to break the data into striped blocks or chunks, making the approach far faster and simpler to implement. For example, data may be striped directly onto the array as 64 bit words"
"190 to 200 Mbytes/s of sustained read throughput, and up to 120Mbytes/s of sustained write throughput"
Support for up to 512MBytes of storage cache RAM
Five integrated ATA UDMA-5 (100MB/s) ports for direct connection to parallel ATA drives or SATA 150 drives via ATA-SATA bridge devices
"However, off the shelf ATA and SATA drives may be utilized directly; i.e., no special synchronization or spindle-sync hardware is required as with original RAID 3"
"Figure 1 illustrates how 64-bit data word destined for the drive array in aSyncRAID controller is handled veruss a legacy RAID controller. For a legacy RAID 16-bit ATA implementation, a block of 64-bit data words from a host bus is divided into a stream of 16-bit words and issued to individual drives until the block stripe is full or the block write is complete. If the block occupies more than a single drive stripe block or "chunk" then it moves onto the next drive to start using another stripe block until the entire block transfer has completed. As we shall see later, the parity generation or update method very much dictates the performance of array write operations.
SyncRAID, due to its innovative synchronization scheme, removes this data and blocking arrangement altogther, keeping the data words intact as 64 bits all the way to the drives. This effectively creates a 4x-speed ATA interface. Applying the concept to multiple SATA drives, the interface becomes a 4x SATA interface, and so on."
"the effective data rate becomes ATA400. For SATA150 drives, the overall rate becomes an effective SATA600"
of course that is burst not STR
"In the case of RAID XL3, the data is simply written to the array and the parity data is overwritten with the new parity information, on the fly in a single step"