Monitoring Storage Gateway

In this section, you can find information about how to monitor a gateway, including monitoring resources associated with the gateway and monitoring the upload buffer and cache storage. You use the AWS Management Console to view metrics for your gateway. For example, you can view the number of bytes used in read and write operations, the time spent in read and write operations, and the time taken to retrieve data from the AWS cloud. With metrics, you can track the health of your gateway and set up alarms to notify you when one or more metrics fall outside a defined threshold.

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AWS Storage Gateway provides Amazon CloudWatch metrics at no additional charge. Storage Gateway metrics are recorded for a period of two weeks. By using these metrics, you can access historical information and get a better perspective on how your gateway and volumes are performing. For detailed information about CloudWatch, see the Amazon CloudWatch User Guide.

Understanding Gateway Metrics

For the discussion in this topic, we define gateway metrics as metrics that are scoped to the gateway—that is, they measure something about the gateway. Because a gateway contains one or more volumes, a gateway-specific metric is representative of all volumes on the gateway. For example, the CloudBytesUploaded metric is the total number of bytes that the gateway sent to the cloud during the reporting period. This metric includes the activity of all the volumes on the gateway.

When working with gateway metric data, you specify the unique identification of the gateway that you are interested in viewing metrics for. To do this, you specify both the GatewayId and the GatewayName values. When you want to work with metric for a gateway, you specify the gateway dimension in the metrics namespace, which distinguishes a gateway-specific metric from a volume-specific metric. For more information, see Using Amazon CloudWatch Metrics.

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Dimensions for AWS Storage Gateway Metrics

Metric	Description	Applies To
`CacheHitPercent`	Percent of application reads served from the cache. The sample is taken at the end of the reporting period. Unit: Percent	File, cached-volume, and tape gateways.
`CachePercentUsed`	Percent use of the gateway's cache storage. The sample is taken at the end of the reporting period. Unit: Percent	File, cached-volume, and tape gateways.
`CachePercentDirty`	Percent of the gateway's cache that has not been persisted to AWS. The sample is taken at the end of the reporting period. Unit: Percent	File, cached-volume, and tape gateways.
`CloudBytesDownloaded`	The total number of compressed bytes that the gateway downloaded from AWS during the reporting period. Use this metric with the `Sum` statistic to measure throughput and with the `Samples` statistic to measure input/output operations per second (IOPS). Unit: Bytes	File, cached-volume, stored-volume, and tape gateways.
`CloudDownloadLatency`	The total number of milliseconds spent reading data from AWS during the reporting period. Use this metric with the `Average` statistic to measure latency. Unit: Milliseconds	File, cached-volume, stored-volume, and tape gateways.
`CloudBytesUploaded`	The total number of compressed bytes that the gateway uploaded to AWS during the reporting period. Use this metric with the `Sum` statistic to measure throughput and with the `Samples` statistic to measure IOPS. Unit: Bytes	Amazon CloudWatch log groups, and file, cached-volume, stored-volume, and tape gateways.
`UploadBufferFree`	The total amount of unused space in the gateway's upload buffer. The sample is taken at the end of the reporting period. Unit: Bytes	Cached-volume and tape gateways.
`CacheFree`	The total amount of unused space in the gateway's cache storage. The sample is taken at the end of the reporting period. Unit: Bytes	File, cached-volume, and tape gateways.
`UploadBufferPercentUsed`	Percent use of the gateway's upload buffer. The sample is taken at the end of the reporting period. Unit: Percent	Cached-volume and tape gateways.
`UploadBufferUsed`	The total number of bytes being used in the gateway's upload buffer. The sample is taken at the end of the reporting period. Unit: Bytes	Cached-volume and tape gateways.
`CacheUsed`	The total number of bytes being used in the gateway's cache storage. The sample is taken at the end of the reporting period. Unit: Bytes	File, cached-volume, and tape gateways.
`QueuedWrites`	The number of bytes waiting to be written to AWS, sampled at the end of the reporting period for all volumes in the gateway. These bytes are kept in your gateway's working storage. Unit: Bytes	File, cached-volume, stored-volume, and tape gateways.
`ReadBytes`	The total number of bytes read from your on-premises applications in the reporting period for all volumes in the gateway. Use this metric with the `Sum` statistic to measure throughput and with the `Samples` statistic to measure IOPS. Unit: Bytes	File, cached-volume, and stored-volume gateways.
`ReadTime`	The total number of milliseconds spent to do read operations from your on-premises applications in the reporting period for all volumes in the gateway. Use this metric with the `Average` statistic to measure latency. Unit: Milliseconds	File, cached-volume, and stored-volume gateways.
`TotalCacheSize`	The total size of the cache in bytes. The sample is taken at the end of the reporting period. Unit: Bytes	File, cached-volume, and tape gateways.
`WriteBytes`	The total number of bytes written to your on-premises applications in the reporting period for all volumes in the gateway. Use this metric with the `Sum` statistic to measure throughput and with the `Samples` statistic to measure IOPS. Unit: Bytes	File, cached-volume, and stored-volume gateways.
`WriteTime`	The total number of milliseconds spent to do write operations from your on-premises applications in the reporting period for all volumes in the gateway. Use this metric with the `Average` statistic to measure latency. Unit: Milliseconds	File, cached-volume, and stored-volume gateways.
`TimeSinceLastRecoveryPoint`	The time since the last available recovery point. For more information, see Your Cached Gateway is Unreachable And You Want to Recover Your Data. Unit: Seconds	Cached volumes and stored volumes.
`WorkingStorageFree`	The total amount of unused space in the gateway's working storage. The sample is taken at the end of the reporting period. Unit: Bytes	Stored volumes only.
`WorkingStoragePercentUsed`	Percent use of the gateway's upload buffer. The sample is taken at the end of the reporting period. Unit: Percent	Stored volumes only.
`WorkingStorageUsed`	The total number of bytes being used in the gateway's upload buffer. The sample is taken at the end of the reporting period. Unit: Bytes	Stored volumes only.
`UserCpuPercent`	Percent of CPU time spent on gateway processing, averaged across all cores. Unit: Percent	File gateways only.
`IoWaitPercent`	Percent of time that the gateway is waiting on a response from the local disk. Unit: Percent	File gateways only.
`MemTotalBytes`	Amount of RAM provisioned to the gateway VM, in bytes. Unit: Bytes	File gateways only.
`MemUsedBytes`	Amount of RAM currently in use by the gateway VM, in bytes. Unit: Bytes	File gateways only.
`SmbV1Sessions`	Number of SMB version 1 sessions that are active on the gateway. Unit: Number	File gateways only.
`SmbV2Sessions`	Number of SMB version 2 sessions that are active on the gateway. Unit: Number	File gateways only.
`SmbV3Sessions`	Number of SMB version 3 sessions that are active on the gateway. Unit: Number	File gateways only.
`IndexEvictions`	Number of files whose metadata was evicted from the cached index of file metadata to make room for new entries. The gateway maintains this metadata index, which is populated from the AWS Cloud on demand. Statistics: SampleCount for number of directories, SUM for total number of files, Average for average number of files per directory. Unit: Number	File gateways only.
`IndexFetches`	Number of files for which metadata was fetched. The gateway maintains a cached index of file metadata, which is populated from the AWS Cloud on-demand. Statistics: SampleCount for number of directories, SUM for total number of files, Average for average number of files per directory. Unit: Number	File gateways only.

Dimensions for AWS Storage Gateway Metrics

The Amazon CloudWatch namespace for the AWS Storage Gateway service is AWS/StorageGateway. Data is available automatically in 5-minute periods at no charge.

Dimension	Description
`GatewayId`, `GatewayName`	These dimensions filter the data you request to gateway-specific metrics. You can identify a gateway to work by its `GatewayId` or its `GatewayName`. However, note that if the name of your gateway was changed for the time range that you are interested in viewing metrics, then you should use the `GatewayId`. Throughput and latency data of a gateway is based on all the volumes for the gateway. For information about working with gateway metrics, see Measuring Performance Between Your Gateway and AWS.
`VolumeId`	This dimension filters the data you request to volume-specific metrics. Identify a storage volume to work with by its `VolumeId`. For information about working with volume metrics, see Measuring Performance Between Your Application and Gateway.

Dimension

Description

GatewayId, GatewayName

These dimensions filter the data you request to gateway-specific metrics. You can identify a gateway to work by its GatewayId or its GatewayName. However, note that if the name of your gateway was changed for the time range that you are interested in viewing metrics, then you should use the GatewayId.

Throughput and latency data of a gateway is based on all the volumes for the gateway. For information about working with gateway metrics, see Measuring Performance Between Your Gateway and AWS.

VolumeId

This dimension filters the data you request to volume-specific metrics. Identify a storage volume to work with by its VolumeId. For information about working with volume metrics, see Measuring Performance Between Your Application and Gateway.

Monitoring the Upload Buffer

You can find information following about how to monitor a gateway's upload buffer and how to create an alarm so that you get a notification when the buffer exceeds a specified threshold. By using this approach, you can proactively add buffer storage to a gateway before it fills completely and your storage application stops backing up to AWS.

You monitor the upload buffer in the same way in both the cached volume and tape gateway architectures. For more information, see How AWS Storage Gateway Works (Architecture).

Note

The WorkingStoragePercentUsed, WorkingStorageUsed, and WorkingStorageFree metrics represent the upload buffer for the stored volumes setup only before the release of the cached-volume feature in Storage Gateway. Now you should use the equivalent upload buffer metrics UploadBufferPercentUsed, UploadBufferUsed, and UploadBufferFree. These metrics apply to both gateway architectures.

Item of Interest	How to Measure
Upload buffer usage	Use the `UploadBufferPercentUsed`, `UploadBufferUsed`, and `UploadBufferFree` metrics with the `Average` statistic. For example, use the `UploadBufferUsed` with the `Average` statistic to analyze the storage usage over a time period.

To measure upload buffer percent used

Open the CloudWatch console at https://console.aws.amazon.com/cloudwatch/.
Choose the StorageGateway: Gateway Metrics dimension, and find the gateway that you want to work with.
Choose the UploadBufferPercentUsed metric.
For Time Range, choose a value.
Choose the Average statistic.
For Period, choose a value of 5 minutes to match the default reporting time.

The resulting time-ordered set of data points contains the percent used of the upload buffer.

Using the following procedure, you can create an alarm using the CloudWatch console. To learn more about alarms and thresholds, see Creating CloudWatch Alarms.

To set an upper threshold alarm for a gateway's upload buffer

Open the CloudWatch console at https://console.aws.amazon.com/cloudwatch/.
Choose Create Alarm to start the Create Alarm Wizard.
Specify a metric for your alarm.
1. On the Select Metric page of the Create Alarm Wizard, choose the AWS/StorageGateway:GatewayId,GatewayName dimension, and then find the gateway that you want to work with.
2. Choose the UploadBufferPercentUsed metric. Use the Average statistic and a period of 5 minutes.
3. Choose Continue.
Define the alarm name, description, and threshold.
1. On the Define Alarm page of the Create Alarm Wizard, identify your alarm by giving it a name and description in the Name and Description boxes.
2. Define the alarm threshold.
3. Choose Continue.
Configure an email action for the alarm.
1. In the Configure Actions page of the Create Alarm Wizard, choose Alarm for Alarm State.
2. Choose Choose or create email topic for Topic.
  
  To create an email topic means that you set up an Amazon Simple Notification Service (Amazon SNS) topic. For more information about Amazon SNS, see Set Up Amazon SNS.
3. For Topic, type a descriptive name for the topic.
4. Choose Add Action.
5. Choose Continue.
Review the alarm settings, and then create the alarm.
1. In the Review page of the Create Alarm Wizard, review the alarm definition, metric, and associated actions from this step. Associated actions include, for example, sending an email notification.
2. After reviewing the alarm summary, choose Save Alarm.
Confirm your subscription to the alarm topic.
1. Open the Amazon Simple Notification Service (Amazon SNS) email topic that is sent to the email address that you specified when creating the topic.
  
  The following image shows a notification.
2. Confirm your subscription by clicking the link in the email.
  
  A subscription confirmation appears.

Monitoring Cache Storage

You can find information following about how to monitor a gateway's cache storage and how to create an alarm so that you get a notification when parameters of the cache pass specified thresholds. Using this alarm, you know when to proactively add cache storage to a gateway.

You only monitor cache storage in the cached volumes architecture. For more information, see How AWS Storage Gateway Works (Architecture).

Item of Interest How to Measure

Total usage of cache

Item of Interest	How to Measure
Total usage of cache	Use the `CachePercentUsed` and `TotalCacheSize` metrics with the `Average` statistic. For example, use the `CachePercentUsed` with the `Average` statistic to analyze the cache usage over a period of time. The `TotalCacheSize` metric changes only when you add cache to the gateway.
Percentage of read requests that are served from the cache	Use the `CacheHitPercent` metric with the `Average` statistic. Typically, you want `CacheHitPercent` to remain high.
Percentage of cache that is dirty—that is, it contains content that has not been uploaded to AWS	Use the `CachePercentDirty` metrics with the `Average` statistic. Typically, you want `CachePercentDirty` to remain low.

Use the CachePercentUsed and TotalCacheSize metrics with the Average statistic. For example, use the CachePercentUsed with the Average statistic to analyze the cache usage over a period of time.

The TotalCacheSize metric changes only when you add cache to the gateway.

Percentage of read requests that are served from the cache

Use the CacheHitPercent metric with the Average statistic.

Typically, you want CacheHitPercent to remain high.

Percentage of cache that is dirty—that is, it contains content that has not been uploaded to AWS

Use the CachePercentDirty metrics with the Average statistic.

Typically, you want CachePercentDirty to remain low.

To measure the cache's percentage dirty for a gateway and all its volumes

Open the CloudWatch console at https://console.aws.amazon.com/cloudwatch/.
Choose the StorageGateway: Gateway Metrics dimension, and find the gateway that you want to work with.
Choose the CachePercentDirty metric.
For Time Range, choose a value.
Choose the Average statistic.
For Period, choose a value of 5 minutes to match the default reporting time.

The resulting time-ordered set of data points contains the percentage of the cache that is dirty over the 5 minutes.

To measure the cache's percentage dirty for a volume

Open the CloudWatch console at https://console.aws.amazon.com/cloudwatch/.
Choose the StorageGateway: Volume Metrics dimension, and find the volume that you want to work with.
Choose the CachePercentDirty metric.
For Time Range, choose a value.
Choose the Average statistic.
For Period, choose a value of 5 minutes to match the default reporting time.

The resulting time-ordered set of data points contains the percentage of the cache that is dirty over the 5 minutes.

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