CentOS 7 Review. Part 3: NFS, FedFS, pNFS
In the first part of the CentOS 7 review, we talked about Linux container support in Cent OS 7. In the second part, we talked about identity management . The third part of the review is devoted to the NFS network file system and its environment on CentOS 7. At the end of the post is a link to free testing of CentOS 7 in the InfoboxCloud cloud.
Network File System NFS allows remote hosts to mount file systems over a network and interact with these file systems as if they were mounted locally.
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CentOS 7 supports two versions of NFS: v3 and v4. NFSv3 supports secure asynchronous writing and more reliable error handling compared to NFSv2 and supports 64-bit file sizes, allowing clients to access more than two gigabytes of this file. NFSv4 supports firewalling on the Internet, no longer requires the rcpbind service, supports ACL access control lists and uses state operations.
CentOS 7 has added support for network file system NFS 4.1 with improved performance and security, including support for Parallel NFS on the client side. NFS 4.1 no longer requires a separate TCP connection for callbacks, which allows the NFS server to work even for NAT and firewalls.
The new version includes support for the semantics of 'exactly once' (except for reboot operations), which allows to solve the problem when the operation could return an incorrect result, if the answer was lost and the operation was requested twice (provided with state sessions).
NFS 4.1 uses standard network protocols for better performance in congested networks. NFS over TCP allows the latest generation of network cards to use the TCP segmentation offload (TCO) feature, freeing up CPU resources for useful work. When transmitting data using TCP / IP, it is often necessary to break large data blocks into several small ones, this is due to protocol restrictions. This partitioning process is called segmentation. Usually in the segmentation process uses a central processor. A network adapter equipped with the TCP Segmentation feature frees the computer processor from performing the segmentation function and takes over.
To deploy and support safer environments, NFSv4.2 labeled NFS allows you to use SELinux contexts, including secure home directories of virtual machines stored in NFS.
CentOS 7 supports NFSv3, NFSv4 and NFSv4.1 clients. By default, clients attempt to mount NFSv4 and switch to NFSv3 if the attempt fails. NFSv4 requires TCP, while NFSv3 can work over UDP (due to the ability to work on a stateless network). If the server suddenly becomes unavailable, clients working over UDP will continue to send requests to the server. Also, when a frame is lost with UDP, the entire RPC request must be re-transmitted, and when using TCP, only the lost frame must be re-sent. Therefore, it is recommended to use TCP to work with the NFS server.
The mount and lock protocols were included in the NFSv4 protocol. NFSv4 no longer interacts with rcpbind , lockd and rpc.statd . The NFS server still requires rcp.mountd to configure exports, but does not participate in any other operations.
The NFS server settings that allow access to clients are still in / etc / exports . The server is still listening on TCP port 2049, so be sure to allow it in IPTables .
Another interesting feature of CentOS 7 is support for the federated file system FedFS. FedFS provides a set of open protocols that allow you to build scalable namespaces between multiple file servers using the NFSv4 system links available to unmodified NFS clients.
CentOS 7 is developing support for pNFS, which allows NFS to scale to conventional NAS to allow customers to read and write data directly and in parallel to physical storage.
The parallel pNFS architecture allows multiple NFS servers to manage metadata and coordinate access, providing predictable and reliable access to very large data sets from many clients.
pNFS layouts are supported on CentOS 7.
There is no full support for pNFS yet.
Test results pNFS. The study was conducted on Red Hat Enterprise Linux 7 with a 3.10.0.119 RC1 kernel with OracleR2 OLTP. For testing, a cluster of 2 nodes with pNFS clients was used. Nearly 250,000 transactions per minute were reached with 100 users.
Sources used in the preparation of the article:
New world of NFS
NFS & GFS2
RedHat official blog
RedHat Knowledge Base
CentOS Official Blog
Especially for our readers, we provided the opportunity to try CentOS 7 in the InfoboxCloud cloud. Register the trial version for 15 days via this link . If you need more resources for testing than in the trial version - write to trukhinyuri@infoboxcloud.com
Nfs
Network File System NFS allows remote hosts to mount file systems over a network and interact with these file systems as if they were mounted locally.
')
CentOS 7 supports two versions of NFS: v3 and v4. NFSv3 supports secure asynchronous writing and more reliable error handling compared to NFSv2 and supports 64-bit file sizes, allowing clients to access more than two gigabytes of this file. NFSv4 supports firewalling on the Internet, no longer requires the rcpbind service, supports ACL access control lists and uses state operations.
CentOS 7 has added support for network file system NFS 4.1 with improved performance and security, including support for Parallel NFS on the client side. NFS 4.1 no longer requires a separate TCP connection for callbacks, which allows the NFS server to work even for NAT and firewalls.
The new version includes support for the semantics of 'exactly once' (except for reboot operations), which allows to solve the problem when the operation could return an incorrect result, if the answer was lost and the operation was requested twice (provided with state sessions).
NFS 4.1 uses standard network protocols for better performance in congested networks. NFS over TCP allows the latest generation of network cards to use the TCP segmentation offload (TCO) feature, freeing up CPU resources for useful work. When transmitting data using TCP / IP, it is often necessary to break large data blocks into several small ones, this is due to protocol restrictions. This partitioning process is called segmentation. Usually in the segmentation process uses a central processor. A network adapter equipped with the TCP Segmentation feature frees the computer processor from performing the segmentation function and takes over.
To deploy and support safer environments, NFSv4.2 labeled NFS allows you to use SELinux contexts, including secure home directories of virtual machines stored in NFS.
CentOS 7 supports NFSv3, NFSv4 and NFSv4.1 clients. By default, clients attempt to mount NFSv4 and switch to NFSv3 if the attempt fails. NFSv4 requires TCP, while NFSv3 can work over UDP (due to the ability to work on a stateless network). If the server suddenly becomes unavailable, clients working over UDP will continue to send requests to the server. Also, when a frame is lost with UDP, the entire RPC request must be re-transmitted, and when using TCP, only the lost frame must be re-sent. Therefore, it is recommended to use TCP to work with the NFS server.
The mount and lock protocols were included in the NFSv4 protocol. NFSv4 no longer interacts with rcpbind , lockd and rpc.statd . The NFS server still requires rcp.mountd to configure exports, but does not participate in any other operations.
The NFS server settings that allow access to clients are still in / etc / exports . The server is still listening on TCP port 2049, so be sure to allow it in IPTables .
FedFS
Another interesting feature of CentOS 7 is support for the federated file system FedFS. FedFS provides a set of open protocols that allow you to build scalable namespaces between multiple file servers using the NFSv4 system links available to unmodified NFS clients.
pNFS
CentOS 7 is developing support for pNFS, which allows NFS to scale to conventional NAS to allow customers to read and write data directly and in parallel to physical storage.
The parallel pNFS architecture allows multiple NFS servers to manage metadata and coordinate access, providing predictable and reliable access to very large data sets from many clients.
pNFS layouts are supported on CentOS 7.
There is no full support for pNFS yet.
Test results pNFS. The study was conducted on Red Hat Enterprise Linux 7 with a 3.10.0.119 RC1 kernel with OracleR2 OLTP. For testing, a cluster of 2 nodes with pNFS clients was used. Nearly 250,000 transactions per minute were reached with 100 users.
Sources used in the preparation of the article:
New world of NFS
NFS & GFS2
RedHat official blog
RedHat Knowledge Base
CentOS Official Blog
Trial version in the cloud for free
Especially for our readers, we provided the opportunity to try CentOS 7 in the InfoboxCloud cloud. Register the trial version for 15 days via this link . If you need more resources for testing than in the trial version - write to trukhinyuri@infoboxcloud.com
Source: https://habr.com/ru/post/231955/
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