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OceanStor 9000 V300R006C00 File System Feature Guide 12

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Huawei uses machine translation combined with human proofreading to translate this document to different languages in order to help you better understand the content of this document. Note: Even the most advanced machine translation cannot match the quality of professional translators. Huawei shall not bear any responsibility for translation accuracy and it is recommended that you refer to the English document (a link for which has been provided).
Working Principles

Working Principles

The NFS protocol enhancement feature functions by configuring multiple network ports on the client and installing DFSClient.

Multi-Connection Mode

The NFS protocol enhancement feature enables a single Mac OS X or RHEl client to establish multiple data transmission links with the storage system.

Before the optimization

A Mac OS X or Linux client can establish only one link with the storage system when it uses the NFS protocol to share filesdirectory. As shown in Figure 12-1, the client has four network ports but can connect to only one front-end service network port of OceanStor 9000. The bandwidth of this only network port is provided during file transmission. This restricts the performance of OceanStor 9000 as well as wastes the network port resource on the client.

Figure 12-1  Performance bottleneck of single-connection mode

After the optimization

OceanStor 9000 introduces the NFS protocol enhancement feature. By configuring multiple network ports on the client and installing the DFSClient, you can establish multiple links between the client and OceanStor 9000, greatly increasing the bandwidth provided for the client accessing OceanStor 9000 and accelerating data transmission.

Table 12-5 describes the multi-connection modes for two types of clients.

Table 12-5  Multi-connection modes for two types of clients

Client Type

Multi-Connection Mode

Data Transmission Mode

Mac OS X client

One-to-one connection

Link polling

Linux client

Full connection

Link load balancing

Multi-Connection Mode on a Mac OS X Client
This section describes the establishment of multiple connections and the data transmission process on a Mac OS X client.
  1. The Mac OS X client sends a connection request to OceanStor 9000.
  2. OceanStor 9000 returns multiple dynamic front-end service IP addresses. Each of the IP addresses is connected with an IP address on the client, as shown in Figure 12-2.
    Figure 12-2  Establishment of multiple connections on a Mac OS X client
    The number of connections that can be established using DFSClient is the number of IP addresses to be connected on the client (M) or the dynamic front-end service IP addresses of OceanStor 9000 (S), specifically:
    • When M ≥ S:

      OceanStor 9000 returns all the dynamic front-end service IP addresses. The number of connections that can be established is S.

    • When M < S:

      OceanStor 9000 randomly returns M dynamic front-end service IP addresses. The number of connections that can be established is M.

  3. When upper-layer services read and write video files concurrently, the system selects one connection to transmit one file. When all the connections are polled, the system starts a new round of polling, as shown in Figure 12-3.
    Figure 12-3  Data transmission mode on a Mac OS X client

Compared with the single-connection mode, the multi-connection mode increases the bandwidth provided for the Mac OS X client accessing OceanStor 9000.

During multi-layer video editing, video files are accessed concurrently. DFSClient can evenly distribute files to connections, thereby accelerating data transmission.

Multi-Connection Mode on a Linux Client
This section describes the establishment of multiple connections and the data transmission process on a Linux client.
  1. The Linux client sends a connection request to OceanStor 9000.
  2. OceanStor 9000 returns multiple dynamic front-end service IP addresses. Each of the IP addresses is connected with all the IP addresses on the client, as shown in Figure 12-4.
    Figure 12-4  Establishment of multiple connections on a Linux client
    The number of connections that can be established = R x S, where:
    • R indicates the number of IP addresses to be connected on the Linux client.
    • S indicates the number of dynamic front-end service IP addresses returned by OceanStor 9000.
  3. When upper-layer services read and write files concurrently, the system selects the connection with the minimum workload for data transmission, achieving link load balancing, as shown in Figure 12-5.
    Figure 12-5  Data transmission mode on a Linux client

Compared with the single-connection mode, the multi-connection mode increases the bandwidth provided for the Linux client accessing OceanStor 9000.

When there are a great number of data reads and writes, DFSClient can balance workloads among connections and accelerate data transmission.

Cache Optimization

This part introduces cache optimization implemented by DFSClient on the Mac OS X client, including the increase of I/O granularity and prefetch mechanism optimization.

I/O Granularity Increase

The read and write I/O granularity on the Mac OS X client is only 64 KB at most. However, the volume of 4K video data is large, for example. a one-minute video has several GB. For this reason, the client has to interact with OceanStor 9000 frequently for data reading and writing, causing performance bottleneck in the UHD scenario.

Figure 12-6 shows the number of interactions required for the client to read 1024 KB data from OceanStor 9000. When the I/O granularity is only 64 KB, the number of interactions is 16. When the I/O granularity is increased to 1024 KB, only one interaction is required.

Figure 12-6  Comparison before and after I/O granularity is increased

Breaking the limit of the 64 KB I/O granularity, DFSClient supports a maximum of 1024 KB read I/O granularity and 128 KB I/O write granularity, reducing the number of interactions between the Mac OS X client and OceanStor 9000 and effectively utilizing physical bandwidth of ports.

Prefetch Mechanism Optimization

Prefetch on the Mac OS X client refers to that a certain amount of data is read to cache in advanced and upper-layer services read data from cache directly to reduce the number of disk seek times and delay of responding to upper-layer services.

As shown in Figure 12-7, When the cache of the Mac OS X client is sufficient, the cache provides the required data to upper-layer services without reading data from OceanStor 9000. The cache sends read requests to OceanStor 9000 only when the cached data amount is insufficient to meet requirements of upper-layer services. Upper-layer services can obtain the required data after all the data is read in the cache. This prefetch policy causes that many read requests are sent to OceanStor 9000 in a short period, causing long delay to respond to these requests.

Figure 12-7  Prefetch mechanism on the Mac OS X client before the optimization
As shown in Figure 12-8, the NFS protocol enhance feature optimizes the prefetch mechanism on the Mac OS X client by installing DFSClient on the client. After the optimization, when upper-layer services send read requests to the cache, the cache prefetches data from OceanStor 9000. This ensures sufficient data amount in the cache, avoiding read request concentration and reducing delay.
Figure 12-8  Prefetch mechanism on the Mac OS X client after the optimization
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Updated: 2019-06-27

Document ID: EDOC1000122519

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