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Sun ZFS Storage 7000 System Administration Guide
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Document Information

Preface

1.  Introduction

2.  Status

3.  Configuration

4.  Services

5.  Shares

6.  Analytics

Analytics

Introduction

Concepts

Analytics

Drilldown Analysis

Statistics

Datasets

Actions

Worksheets

Statistics

Introduction

Descriptions

Analytics

Advanced Analytics

Default Statistics

Tasks

Statistics Tasks

CPU Percent utilization

CPU: Percent Utilization

Example

When to check

Breakdowns

Further Analysis

Details

Cache ARC accesses

Cache: ARC accesses

When to check

Breakdowns

Details

Metadata

Prefetch

Further Analysis

Cache L2ARC IO bytes

Cache: L2ARC I/O bytes

When to check

Breakdowns

Further Analysis

Cache L2ARC accesses

Cache: L2ARC accesses

When to check

Breakdowns

Further Analysis

Data Movement NDMP bytes transferred tofrom disk

Data Movement: NDMP bytes transferred to/from disk

When to check

Breakdowns

Further Analysis

Data Movement NDMP bytes transferred tofrom tape

Data Movement: NDMP bytes transferred to/from tape

When to check

Breakdowns

Further Analysis

Data Movement Shadow migration bytes

Data Movement: Shadow migration bytes

When to check

Breakdowns

Further Analysis

Data Movement Shadow migration ops

Data Movement: Shadow migration ops

When to check

Breakdowns

Further Analysis

Data Movement Shadow migration requests

Data Movement: Shadow migration requests

When to check

Breakdowns

Further Analysis

Disk Disks

Disk: Disks

When to check

Breakdowns

Interpretation

Further Analysis

Details

Disk IO bytes

Disk: I/O bytes

When to check

Breakdowns

Further Analysis

Disk IO operations

Disk: I/O operations

When to check

Breakdowns

Further Analysis

Network Device bytes

Network: Device bytes

When to check

Breakdowns

Further Analysis

Network Interface bytes

Network: Interface bytes

Example

When to check

Breakdowns

Further Analysis

Protocol SMB operations

Protocol: SMB operations

Example

When to check

Breakdowns

Further Analysis

Protocol Fibre Channel bytes

Protocol: Fibre Channel bytes

Example

When to check

Breakdowns

Further Analysis

Protocol Fibre Channel operations

Protocol: Fibre Channel operations

Example

When to check

Breakdowns

Further Analysis

Protocol FTP bytes

Protocol: FTP bytes

Example

When to check

Breakdowns

Further Analysis

Protocol HTTPWebDAV requests

Protocol: HTTP/WebDAV requests

When to check

Breakdowns

Further Analysis

Protocol iSCSI bytes

Protocol: iSCSI bytes

When to check

Breakdowns

Further Analysis

Protocol iSCSI operations

Protocol: iSCSI operations

When to check

Breakdowns

Further Analysis

Protocol NFSv2 operations

Protocol: NFSv2 operations

Example

When to check

Breakdowns

Further Analysis

Protocol NFSv3 operations

Protocol: NFSv3 operations

When to check

Breakdowns

Further Analysis

Protocol NFSv4 operations

Protocol: NFSv4 operations

Example

When to check

Breakdowns

Further Analysis

Protocol SFTP bytes

Protocol: SFTP bytes

Example

When to check

Breakdowns

Further Analysis

Protocol SRP bytes

Protocol: SRP bytes

Example

When to check

Breakdowns

Further Analysis

Protocol SRP operations

Protocol: SRP operations

Example

When to check

Breakdowns

Further Analysis

CPU CPUs

CPU: CPUs

When to check

Breakdowns

Details

CPU Kernel spins

CPU: Kernel spins

When to check

Breakdowns

Cache ARC adaptive parameter

Cache: ARC adaptive parameter

When to check

Breakdowns

Cache ARC evicted bytes

Cache: ARC evicted bytes

When to check

Breakdowns

Cache ARC size

Cache: ARC size

When to check

Breakdowns

Cache ARC target size

Cache: ARC target size

When to check

Breakdowns

Cache DNLC accesses

Cache: DNLC accesses

When to check

Breakdowns

Cache DNLC entries

Cache: DNLC entries

When to check

Breakdowns

Cache L2ARC errors

Cache: L2ARC errors

When to check

Breakdowns

Cache L2ARC size

Cache: L2ARC size

When to check

Breakdowns

Data Movement NDMP file system operations

Data Movement: NDMP file system operations

When to check

Breakdowns

Data Movement NDMP jobs

Data Movement: NDMP jobs

When to check

Breakdowns

Disk Percent utilization

Disk: Percent utilization

When to check

Breakdowns

Notes

Disk ZFS DMU operations

Disk: ZFS DMU operations

When to check

Breakdowns

Disk ZFS logical IO bytes

Disk: ZFS logical I/O bytes

When to check

Breakdowns

Disk ZFS logical IO operations

Disk: ZFS logical I/O operations

When to check

Breakdowns

Memory Dynamic memory usage

Memory: Dynamic memory usage

When to check

Breakdowns

Memory Kernel memory

Memory: Kernel memory

When to check

Breakdowns

Memory Kernel memory in use

Memory: Kernel memory in use

When to check

Breakdowns

Memory Kernel memory lost to fragmentation

Memory: Kernel memory lost to fragmentation

When to check

Breakdowns

Network IP bytes

Network: IP bytes

When to check

Breakdowns

Network IP packets

Network: IP packets

When to check

Breakdowns

Network TCP bytes

Network: TCP bytes

When to check

Breakdowns

Network TCP packets

Network: TCP packets

When to check

Breakdowns

System NSCD backend requests

System: NSCD backend requests

When to check

Breakdowns

System NSCD operations

System: NSCD operations

When to check

Breakdowns

Open Worksheets

Worksheets

Graph

Quantize Plot

Show Hierarchy

Common

Background Patterns

Saving a Worksheet

Toolbar Reference

CLI

Tips

Tasks

BUI

Saved Worksheets

Introduction

Properties

BUI

CLI

Datasets

Introduction

BUI

CLI

Viewing available datasets

Reading datasets

Suspending and Resuming all datasets

Discarding Data in a Dataset

7.  Integration

Glossary

Cache ARC accesses

Cache: ARC accesses

The ARC is the Adaptive Replacement Cache, and is an in-DRAM cache for filesystem and volume data. This statistic shows accesses to the ARC, and allows its usage and performance to be observed.

When to check

When investigating performance issues, to check how well the current workload is caching in the ARC.

Breakdowns

Available breakdowns of Cache ARC accesses are:

Breakdown
Description
hit/miss
The result of the ARC lookup. hit/miss states are described in the table below.
file name
The file name that was requested from the ARC. Using this breakdown allows hierarchy mode to be used, so that filesystem directories can be navigated.
L2ARC eligibility
This is the eligibility of L2ARC caching, as measured at the time of ARC access. A high level of ARC misses which are L2ARC eligible would suggest that the workload would benefit from 2nd level cache devices.
project
This shows the project which is accessing the ARC.
share
This shows the share which is accessing the ARC.
LUN
This shows the LUN which is accessing the ARC.

As described in Overhead, breakdown such as by file name would be the most expensive to leave enabled.

The hit/miss states are:

hit/miss breakdown
Description
data hits
A data block was in the ARC DRAM cache and returned.
data misses
A data block was not in the ARC DRAM cache. It will be read from the L2ARC cache devices (if available and the data is cached on them) or the pool disks.
metadata hits
A metadata block was in the ARC DRAM cache and returned. Metadata includes the on-disk filesystem framework which refers to the data blocks. Other examples are listed below.
metadata misses
A metadata block was not in the ARC DRAM cache. It will be read from the L2ARC cache devices (if available and the data is cached on them) or the pool disks.
prefetched data/metadata hits/misses
ARC accesses triggered by the prefetch mechanism, not directly from an application request. More details on prefetch follow.

Details

Metadata

Examples of metadata:

Prefetch

Prefetch is a mechanism to improve the performance of streaming read workloads. It examines I/O activity to identify sequential reads, and can issue extra reads ahead of time so that the data can be in cache before the application requests it. Prefetch occurs before the ARC by performing accesses to the ARC - bear this in mind when trying to understand prefetch ARC activity. For example, if you see:

Type
Description
prefetched data missess
prefetch identified a sequential workload, and requested that the data be cached in the ARC ahead of time by performing ARC accesses for that data. The data was not in the cache already, and so this is a "miss" and the data is read from disk. This is normal, and is how prefetch populates the ARC from disk.
prefeteched data hits
prefetch identified a sequential workload, and requested that the data be cached in the ARC ahead of time by performing ARC accesses for that data. As it turned out, the data was already in the ARC - so these accesses returned as "hits" (and so the prefetch ARC access wasn't actually needed). This happens if cached data is repeatedly read in a sequential manner.

After data has been prefetched, the application may then request it with its own ARC accesses. Note that the sizes may be different: prefetch may occur with a 128 Kbyte I/O size, while the application may be reading with an 8 Kbyte I/O size. For example, the following doesn't appear directly related:

However it may be: if prefetch was requesting with a 128 KByte I/O size, 23 x 128 = 2944 Kbytes. And if the application was requesting with an 8 Kbyte I/O size, 368 x 8 = 2944 Kbytes.

Further Analysis

To investigate ARC misses, check that the ARC has grown to use available DRAM using Cache: ARC size.