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SAN 通过 VAAI Copy Offload 的低吞吐量增加了延迟

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适用于

  • ONTAP 9
  • VAAI 复制卸载
  • vMotion

问题描述

  • System Manager 仪表板显示高 LUN 延迟,而不会显著提高 IOPS 或吞吐量。
  • 高延迟主要与 SAN 其他操作有关。
  • QOS 统计数据列出了数据层的高延迟。 
 ::> qos statistics volume latency show -vserver SVM1 -volume volume1 Workload ID Latency Network Cluster Data Disk QoS Max QoS Min NVRAM Cloud FlexCache SM Sync VA AVSCAN --------------- ------ ---------- ---------- ---------- ---------- ---------- ---------- ---------- ---------- ---------- ---------- ---------- volume1 5935 321.31ms 143.00us 5.00us 321.15ms 0ms 0ms 0ms 10.00us 0ms 0ms 0ms 0ms volume1 5935 200.02ms 132.00us 5.00us 199.88ms 0ms 0ms 0ms 9.00us 0ms 0ms 0ms 0ms volume1 5935 263.63ms 76.00us 14.00us 263.52ms 18.00us 0ms 0ms 4.00us 0ms 0ms 0ms 0ms volume1 5935 289.97ms 132.00us 4.00us 289.82ms 0ms 0ms 0ms 9.00us 0ms 0ms 0ms 0ms volume1 5935 340.44ms 128.00us 7.00us 340.29ms 0ms 0ms 0ms 7.00us 0ms 0ms 0ms 0ms 
  •  HDD read/write or SSD read/write is much higher than FCP in/out or iSCSI in/out from the sysstat -x outputs.
    • 如果 VAAI Copy Offload 源卷和目标卷来自同一个节点,Net in/out低至 FCP in/outiSCSI in/outsysstat -x
    • 如果 VAAI Copy Offload 源卷和目标卷来自不同的节点,Net in/out高达 HDD read/writeSSD read/writesysstat -x

示例 1: 

System Manager dashboard displays a high LUN latency

注:

  • iSCSI + HDD
  • VAAI 复制卸载源卷和目标卷在同一节点上
  • Net in/outiSCSI in/out 都远低于 HDD read/write

示例 2:

System Manager dashboard displays a high LUN latency

注: 

  • FCP + SSD
  • 源卷和目标卷来自不同节点
  • 这是源节点
  • Net out与 SSD 读取一样高,并且它们都远高于 FCP out

示例 3: 

SAN increased latency with low throughput from VAAI Copy Offload

注:

  • FCP + SSD
  • 源卷和目标卷来自不同节点
  • 这是目标节点
  • Net inSSD write 一样高,并且它们都远高于 FCP in
  • 如果使用 AFD 策略配置 SMas,则在这些 vMotion/复制卸载工作负载期间,甚至 CPU 也可能过高 

 

 

 

 

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