File systems cannot allocate their own vnodes; they must use the functions provided by the VFS to create and manage vnodes. When a client of the VFS requests a new vnode, the vnode allocation code can reuse an old vnode object that is no longer in use. By convention, each open file handle holds a reference as do VM objects backed by files. A vnode with a reference count of 1 or more will not be deallocated or reused to point to a different file.
So, if you want to ensure that your vnode doesn't become a different file under you, you better be sure you have a reference to it. A vnode that points to a valid file and has a reference count of 1 or more is called active. When a vnode's reference count drops to zero, it becomes inactive , that is, a candidate for reuse. An inactive vnode still refers to a valid file and one can try to reactivate it using vget 9 this is used a lot by caches. Before the VFS can reuse an inactive vnode to refer to another file, it must clean all information pertaining to the old file.
A cleaned out vnode is called a reclaimed vnode. To support forceable unmounts and the revoke 2 system call, the VFS may reclaim a vnode with a positive reference count. The reclaimed vnode is given to the dead file system, which returns errors for most operations. The reclaimed vnode will not be reused for another file until its reference count hits zero.
The getnewvnode 9 call allocates a vnode from the pool, possibly reusing an inactive vnode, and returns it to the caller. The vref 9 call increments the reference count on the vnode. It may only be on a vnode with reference count of 1 or greater. The vrele 9 and vput 9 calls decrement the reference count. In addition, the vput 9 call also releases the vnode lock. The vget 9 call, when used on an inactive vnode, will make the vnode active by bumping the reference count to one. When called on an active vnode, vget increases the reference count by one.
V2 Replication. Getting Started. CRUD Operations. Object Modeling. C Sharp. Creating Objects. Reading Objects. Updating Objects. Deleting Objects. Content Types. Using MapReduce. Using Secondary Indexes. Using Commit Hooks. Creating Search Schemas. Searching with Data Types. Implementing a Document Store. Custom Extractors. Conflict Resolution. Data Types. Application Guide. Replication Properties. Write Once. Advanced MapReduce. Cluster Metadata. Client Libraries.
Backend API. Get Bucket Properties. Set Bucket Properties. Reset Bucket Properties. List Buckets. List Keys. Fetch Object. Store Object. Delete Object. List Resources. Search Query. Search Index Info. Fetch Search Index. Store Search Index. Delete Search Index. Fetch Search Schema. Store Search Schema. Link Walking. Protocol Buffers API. Server Info. Get Bucket Type. Set Bucket Type. Data Type Fetch. Data Type Union.
Data Type Store. Data Type Counter Store. Data Type Set Store. Data Type Map Store. Yokozuna Index Get. Yokozuna Index Put. Yokozuna Index Delete. Yokozuna Schema Get. Yokozuna Schema Put. Release notes DataStax Enterprise release notes cover cluster requirements, upgrade guidance, components, security updates, changes and enhancements, issues, and resolved issues for DataStax Enterprise 5.
Installing DSE DataStax Enterprise can be installed in a number of ways, depending on the purpose of the installation, the type of operating system, and the available permissions. Configuration Information about configuring DataStax Enterprise , such as recommended production setting, configuration files, snitch configuration, start-up parameters, heap dump settings, using virtual nodes, and more.
Start-up parameters Switches to change the JVM settings at start up. Choosing a compaction strategy How to choose the best compaction strategy. Configuring Virtual Nodes Topics about setting up and enabling virtual nodes vnodes.
Virtual node vnode configuration A description of virtual nodes vnodes and how to use them in different types of datacenters. Operations DataStax Enterprise operation topics, such as node and datacenter operations, changing replication strategies, configuring compaction and compression, caching, and tuning Bloom filters.
DSE requires the same token architecture on all nodes in a datacenter. A single-token architecture search datacenter no vnodes. An analytics datacenter with vnodes. Set the number of vnode tokens based on the workload distribution requirements of the datacenter: Table 1. If nodes are added concurrently, the algorithm assigns the same tokens to different nodes.
Important: If you do not use vnodes, you must make sure that each node is responsible for roughly an equal amount of data. To ensure that each node is responsible for an equal amount of data, assign each node an initial-token value and calculate the tokens for each datacenter as described in Generating tokens.
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