6.3.4.3 Exadataメトリックを使用したExadataスマートFlash Logの監視

Exadata Smart Flash Logに関連するExadataメトリックでは、1秒当たりの書込みMB数など、Flash Logの使用率に関する情報が提供されます。Flash Logのメトリックは、objectType=FLASHLOGであるMETRICCURRENT、METRICDEFINITIONおよびMETRICHISTORYオブジェクトで識別されます。

例6-4 Flash Logのメトリック定義の表示

この例は、Oracle Exadata System Softwareで使用可能なFlash Logのメトリック定義を表示する方法を示しています。

CellCLI> LIST METRICDEFINITION ATTRIBUTES NAME,DESCRIPTION WHERE OBJECTTYPE = FLASHLOG
         FL_ACTUAL_OUTLIERS              "The number of times redo writes to flash and disk both exceeded the outlier threshold"
         FL_BY_KEEP                      "The amount of  redo data saved on flash due to disk I/O errors"
         FL_DISK_FIRST                   "The number of times redo writes first completed to disk"
         FL_DISK_IO_ERRS                 "The number of disk I/O errors encountered by Smart Flash Logging"
         FL_EFFICIENCY_PERCENTAGE        "The efficiency of Smart Flash Logging expressed as a percentage"
         FL_EFFICIENCY_PERCENTAGE_HOUR   "The efficiency of Smart Flash Logging over the last hour expressed as a percentage"
         FL_FLASH_FIRST                  "The number of times redo writes first completed to flash"
         FL_FLASH_IO_ERRS                "The number of flash I/O errors encountered by Smart Flash Logging"
         FL_FLASH_ONLY_OUTLIERS          "The number of times redo writes to flash exceeded the outlier threshold"
         FL_IO_DB_BY_W                   "The number of MB written to hard disk by Smart Flash Logging"
         FL_IO_DB_BY_W_SEC               "The rate which is the number of MB per second written to hard disk by Smart Flash Logging"
         FL_IO_FL_BY_W                   "The number of MB written to flash by Smart Flash Logging"
         FL_IO_FL_BY_W_SEC               "The rate which is the number of MB per second written to flash by Smart Flash Logging"
         FL_IO_TM_W                      "Cumulative latency of all redo log writes"
         FL_IO_TM_W_RQ                   "Average latency of all redo log writes"
         FL_IO_W                         "The number of writes serviced by Smart Flash Logging"
         FL_IO_W_SKIP_BUSY               "The number of redo writes that could not be serviced by Smart Flash Logging because too much data had not yet been written to disk"
         FL_IO_W_SKIP_BUSY_MIN           "The number of redo writes during the last minute that could not be serviced by Smart Flash Logging because too much data had not yet been written to disk"
         FL_IO_W_SKIP_DISABLED_GD        "The number of redo writes that could not be serviced by Smart Flash Logging because it was disabled for the redo log's grid disk"
         FL_IO_W_SKIP_IORM_LIMIT         "The number of redo writes that could not be serviced by Smart Flash Logging because the IORM limit had been reached for the redo log's grid disk"
         FL_IO_W_SKIP_IORM_PLAN          "The number of redo writes that could not be serviced by Smart Flash Logging because it was disabled by the IORM plan"
         FL_IO_W_SKIP_LARGE              "The number of large redo writes that could not be serviced by Smart Flash Logging because the size of the data was larger than the amount of available space on any flash disk"
         FL_IO_W_SKIP_LOG_ON_FAST_DEV    "The number of redo writes that bypassed Smart Flash Logging because the redo log resides on a fast device"
         FL_IO_W_SKIP_NO_BUFFER          "The number of redo writes that could not be serviced by Smart Flash Logging because of lack of available buffers"
         FL_IO_W_SKIP_NO_FL_DISKS        "The number of redo writes that could not be serviced by Smart Flash Logging because there were no available Flash Log disks"
         FL_PREVENTED_OUTLIERS           "The number of times redo writes to disk exceeded the outlier threshold; these would have been outliers had it not been for Smart Flash Logging"
         FL_RQ_TM_W                      "Cumulative latency of all redo log write requests (includes network and other processing overhead)"
         FL_RQ_TM_W_RQ                   "Average latency of all redo log write requests"
         FL_RQ_W                         "The number of redo log write requests serviced (includes requests which were not handled by Smart Flash Logging)"
         FL_SKIP_OUTLIERS                "The number of times redo writes to disk exceeded the outlier threshold when Smart Flash Logging was not used"

次の追加詳細に注意してください。

• FL_RQ_TM_Wは、REDOログ書込みリクエストの累積レイテンシ(ネットワーキングおよびその他のオーバーヘッドを含む)を追跡します。オーバーヘッド・コンポーネントを特定し、ネットワークや処理などの要因によるレイテンシ・オーバーヘッドを取得するには、FL_RQ_TM_WからのFL_IO_TM_Wの減算を使用できます。

• FL_SKIP_OUTLIERSは、REDOログ書込みでFlash Logの使用がスキップされたときの外れ値の数を追跡します。外れ値は0.5秒を超えたREDOログ書込みです。

  また、FL_IO_W_SKIPで始まるメトリックは、Flash Logが使用されないその他の状況を追跡します。

• ディスクとフラッシュ・ストレージに同時に書き込むとき、ディスク・コントローラの書込みキャッシュは、フラッシュよりも高速に一部の書込みを吸収できます。そのため、ディスクへのREDOログ書込み操作のかなりの部分がフラッシュよりも前に完了するのは正常です。場合によっては、FL_DISK_FIRSTの値がFL_FLASH_FIRSTの値を超えることがあります。ただし、このことは、Exadataスマート・フラッシュ・ロギング機能が効果がないことや不要であることを意味しません。