本文详细介绍了磁盘条带化技术中的粗粒度和细粒度条带的概念及应用。粗粒度条带适用于多并发I/O请求场景，通过一组条带化磁盘服务大量并发I/O请求，最大化整体I/O吞吐量；细粒度条带则适用于少量大型I/O请求的场景，通过多磁盘服务单一I/O请求，提高响应时间。
Coarse grain striping allows a disk in the array to service several I/O requests. In this
way, a large number of concurrent I/O requests can be serviced by a set of striped
disks with minimal I/O setup costs. Coarse grain striping strives to maximize overall
I/O throughput. multiblock reads, as in full table scans, will benefit when stripe
depths are large and can be serviced from one drive. Parallel query in a DSS
environment is also a candidate for coarse grain striping. This is because there are
many individual processes, each issuing separate I/Os. If coarse grain striping is used
in systems that do not have high concurrent requests, then hot spots could result.
In a system with a few large I/O requests, such as in a traditional DSS environment or
a low-concurrency OLTP system, then it is beneficial to keep the stripe depth small.
This is called fine grain striping. In such systems, the stripe depth is
n * DB_BLOCK_SIZE
where n is smaller than the multiblock read parameters, such as DB_FILE_
MULTIBLOCK_READ_COUNT.
Fine grain striping allows a single I/O request to be serviced by multiple disks. Fine
grain striping strives to maximize performance for individual I/O requests or
way, a large number of concurrent I/O requests can be serviced by a set of striped
disks with minimal I/O setup costs. Coarse grain striping strives to maximize overall
I/O throughput. multiblock reads, as in full table scans, will benefit when stripe
depths are large and can be serviced from one drive. Parallel query in a DSS
environment is also a candidate for coarse grain striping. This is because there are
many individual processes, each issuing separate I/Os. If coarse grain striping is used
in systems that do not have high concurrent requests, then hot spots could result.
In a system with a few large I/O requests, such as in a traditional DSS environment or
a low-concurrency OLTP system, then it is beneficial to keep the stripe depth small.
This is called fine grain striping. In such systems, the stripe depth is
n * DB_BLOCK_SIZE
where n is smaller than the multiblock read parameters, such as DB_FILE_
MULTIBLOCK_READ_COUNT.
Fine grain striping allows a single I/O request to be serviced by multiple disks. Fine
grain striping strives to maximize performance for individual I/O requests or
response time
粗粒度条带允许一个磁盘在阵列中服务几个IO的要求。通过这种方法，大量的并发IO要求
可以通过一组条带化磁盘提供服务使用最小化的IO消耗成本。粗粒度条带使用得可以最大化
整个IO的吞吐量。多块读取，比如全表扫描，适合当条带化的深度足够大并且可以通过一个
驱动器提供服务。并发查询对于一个DSS环境也是一个可选方案对于粗粒度条带。这是因为存在
非常多的独立进程，每个发出独立的IO。如果粗粒度条带用在没有要求高并发的系统，那么
会产生热点结果。对于部份有大量IO需求的系统，比如在一个传统的DSS环境或者一个低并发的
OLTP系统，那么它适宜保持小的条带化深度。这个叫作细粒度条带。在这种情况下，条带深度是
N*DB_BLOCK_SIZE
N是一个小于多块读取的参数，比如DB_FILE_MULTIBLOCK_READ_COUNT.
细粒度条带允许一个单独IO要求通过多个磁盘提供服务。细粒度条带使得最大化性能对于独立的IO
要求或者反应时间。
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