Big Blocks

"Big Blocks" is a feature that allows MAGIC customers to expand their disk space by increasing the maximum available disk storage on a single segment up to eight times. MEDITECH supports Big Blocks on the following server classes: EMC's Intel-based AViiON servers, Compaq's Alpha 1000, 1000A, and DS10 servers, and all MAGIC on Windows® 2000 configurations from Compaq, Dell, and IBM.

Our MAGIC operating system calls its disk storage databases segments; there can be up to eight segments on a single machine. Each segment is divided into as many as 8 million "blocks" -- chunks of disk that store data.

The blocks within a MAGIC segment are organized into a hierarchy known as a balanced B-tree structure. Upper-level blocks have name indexes that point to lower-level blocks. The lower-level blocks contain the application data.

Big Blocks conversion involves an increase in the physical size limitation of each block. It is a redefinition of the block size. In MAGIC, blocks were traditionally comprised of two disk sectors housing 1K bytes of data storage. Given the limit of 8 million blocks per segment, this meant an entire segment could hold up to 8GB of data.

There are two classifications of Big Blocks -- 4K and 8K. MEDITECH has redefined each block to be a total of either 4K bytes (eight disk sectors) or 8K bytes (16 disk sectors). The conversion process involves reading each block from a source disk and writing it to a converted disk. Instead of copying each block to two consecutive disk sectors, the Big Blocks conversion copies the source block to the target disk using eight or 16 sectors. With blocks now up to 8K bytes (8,192 bytes) large, each segment on the MAGIC system can now hold up to 64GB of data -- an eightfold increase. (Please note that 1K blocks can be converted into 4K blocks and 4K blocks can be converted into 8K blocks. However, 1K blocks cannot be converted into 8K blocks.)

MEDITECH introduced support for the optional 8K block size with the P7.0 release of the MAGIC Operating System. MEDITECH only recommends 8K blocks on EMC Intel-based AViiONs, Compaq AlphaServer DS10s, and the new MAGIC on Windows 2000 configurations from Compaq, Dell, and IBM.

When users perform a Big Blocks conversion on their MAGIC system, they realize the following benefits:

• More storage space for current data
• An increase of the buffer pool (data cache) to 128 MB (4K blocks) or 256 MB (8K blocks) that results in an increase in the amount of data that can be cached.

Furthermore, the increased storage capacity of the blocks means the system is less likely to be Split Active. A Split Active state occurs when a disk block has been filled and must "split" in order to add more data. Often, when the file is Split Active, no other jobs can access that file. Since each segment block is enlarged in Big Blocks, the chances of a block filling to capacity are reduced significantly. The reduction in probability of splitting upper level blocks in the B-tree is exponential.

Big Blocks is not a solution for archiving or long-term storage of data. For those needs, MEDITECH recommends the following:

• MEDITECH's Data Archiving application for long-term storage of departmental, clinical, and financial data
• MEDITECH's Data Repository for long-term storage of research-based data.