16 1.Storage Design 1.2Examining Shared Storage Fundamentals a The elements that make up a shared storage array consist of external connectivity, storage processors, array software, cache memory disks, and bandwidth Array Software o Although hardware specifications are important and can define the scaling limits of the array, just as important are the functional capabilities the array software provides o The capabilities of modern storage arrays are vast, similar in scope to vSphere itself, and vary wildly among vendors 河南中医药大学/阮晓龙/13938213680/htp/cloudxg.hactcm.edu.cn/http:/www5ucwebcn
17 1.Storage Design 1.2Examining Shared Storage Fundamentals a The elements that make up a shared storage array consist of external connectivity, storage processors, array software, cache memory disks, and bandwidth Cache Memory o Every array differs as to how cache memory is implemented, but all have some degree of nonvolatile memory used for various caching functions, delivering lower latency and higher lOPS throughput by buffering I /O using write caches and storing commonly read data to deliver a faster response time using read caches o Nonvolatility(meaning the ability to survive a power loss) is critical for write caches because the data is not yet committed to disk, but it's not critical for read caches Cached performance is often used when describing shared storage array performance maximums(in IOPS, MBps, or latency)in specification sheets 河南中医药大学/阮晓龙/13938213680/htp/cloudxg.hactcm.edu.cn/http:/www5ucwebcn
18 1.Storage Design 1.2Examining Shared Storage Fundamentals a The elements that make up a shared storage array consist of external connectivity, storage processors, array software, cache memory disks, and bandwidth Cache Memory a These results generally do not reflect real-world scenarios. In most real world scenarios, performance tends to be dominated by the disk performance(the type and number of disks) and is helped by write caches in most cases, but only marginally by read caches(with the exception of large relational database management systems, which depend heavily on read ahead cache algorithms a One vSphere use case helped by read caches is a situation where many boot images are stored only once(through the use of vSphere or storage array technology), but this is also a small subset of the overall VM lyO pattern 河南中医药大学/阮晓龙/13938213680/htp/cloudxg.hactcm.edu.cn/http:/www5ucwebcn
9 1.Storage Design 1.2Examining Shared Storage Fundamentals a The elements that make up a shared storage array consist of external connectivity, storage processors, array software, cache memory disks, and bandwidth Disks o Arrays differ as to which type of disks(often called spindles) they support and how many they can scale to support o Drive capabilities are defined by a number of attributes First, drives are often separated by the drive interface they use: Fibre Channel serial-attached SCSI (SAS), and serial ATA (SATA). With the exception of enterprise flash drives(EFDs), drives are typically described by their rotational speed, noted in revolutions per minute(RPM). Fibre Channel drives typically come in 15K RPM and 10K RPM variants, SATA drives are usually found in 5400 RPM and 7200 RPM variants, and SAS drives are usually 15K RPM or 10K RPM variants 河南中医药大学/阮晓龙/13938213680/htp/cloudxg.hactcm.edu.cn/http:/www5ucwebcn
20 1.Storage Design 1.2Examining Shared Storage Fundamentals a The elements that make up a shared storage array consist of external connectivity, storage processors, array software, cache memory disks, and bandwidth Disks o Arrays differ as to which type of disks(often called spindles) they support and how many they can scale to support o Drive capabilities are defined by a number of attributes Second, EFDS, which are now mainstream, are solid state and have no moving parts; therefore, rotational speed does not apply(nor does the name spindle).The type and number of disks are very important. Coupled with how they are configured, this determines how a storage object(either a LUN for a block device or a file system for a NAS device) performs Shared storage vendors generally use disks from the same disk vendors, so this is an area of commonality across shared storage vendors 河南中医药大学/阮晓龙/13938213680/htp/cloudxg.hactcm.edu.cn/http:/www5ucwebcn