| | 52 | * it’s direct attached storage (DAS) or some type of Storage Area Network (SAN) storage. In some cases, you can combine various types of storage. |
| | 53 | * GPFS -> high-speed, parallel, distributed file system. GPFS achieves high-performance by striping data across multiple disks on multiple storage devices. |
| | 54 | * 使用三種 striping 方式： |
| | 55 | 1. '''''Round Robin''''' |
| | 56 | 2. '''''Random''''' |
| | 57 | 3. '''''Balanced Random''''' |
| | 58 | * To further improve performance, GPFS uses client-side caching and deep prefetching such as '''''read-ahead and write-behind'''''. It recognizes standard '''''access patterns''''' (sequential, reverse sequential, and random) and will optimize I/O accesses for these particular patterns. Furthermore GPFS can read or write large blocks of data in a single I/O operation. |
| | 59 | * '''''Block size''''' 可選擇 16KB, 64KB, 256KB, 512KB, 1MB, and 2MB block sizes are supported with 256K being the most common |
| | 60 | * large block sizes helps improve performance when large data accesses are common |
| | 61 | * Small block sizes are used when small data accesses are common |
| | 62 | * GPFS subdivides the blocks into '''''32 sub-blocks'''''. |
| | 63 | * Block is a largest chunk of contiguous data that can be accessed. A sub-block is the smallest contiguous data that can be accessed. Sub-blocks are useful for files that are smaller than a block and are stored using the sub-blocks. This can help the performance of applications that use lots of small data files (i.e. life sciences applications). |
| | 64 | * High Availability (HA) -> GPFS uses distributed metadata so that there is no single point of failure, nor a performance bottleneck. GPFS can be configured to use logging and replication. GPFS will log (journal) the metadata of the file system. |
| | 65 | * GPFS can also be configured for fail-over both at a disk level and at a server level |
| | 66 | * GPFS 現今依舊有在使用，in the Linux world, there are GPFS clusters with over 2,400 nodes (clients). One aspect of GPFS that should be mentioned in this context is that the GPFS is priced by the node for both I/O nodes and clients. |
| | 67 | * GPFS 版本： |
| | 68 | * 3 -> only uses TCP as the transport protocol |
| | 69 | * 4 -> have native IB protocols |
| | 70 | * In addition, the I/O nodes of GPFS can act as NFS servers if NFS is required. |
| | 71 | * Feature -> multi-cluster. This allows two different GPFS file systems to be connected over a network.This is a great feature for groups in disparate locations to share data |
| | 72 | * last feature -> GPFS Open Source Portability Layer. \The portability layer allows these GPFS kernel modules to communicate with |
| | 73 | the Linux kernel. A way to create a bridge from the GPL kernel to a non-GPL set of |
| | 74 | kernel modules, it actually serves a very useful purpose. |
| | 75 | |
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