Essentially the same, are the underlying block storage but inconsistent performance on the external interfaces, respectively, applied to different business scenarios .
Distributed storage application scenarios with respect to its storage interface, and now popular divided into three types:
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Object storage: that is, in the usual sense of the key-value store, its interface is simple GET, PUT, DEL and other extensions, such as the seven cows, they shoot, Swift, S3
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Block storage: This interface typically QEMU Driver Kernel Module manner or present, such an interface needs to implement Block Driver Interface Block Device Interface for Linux or QEMU provided, such as Sheepdog, AWS of EBS, hard and cloud Yun aliyun Banko system, as well as Ceph of RBD (RBD memory is block-oriented interface Ceph)
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File storage: the usual sense is to support the POSIX interface, such as with a traditional file system Ext4 is a type, but the difference is that the distributed storage offers the ability to parallelization, such as Ceph's CephFS (CephFS is Ceph file-oriented storage interface) but sometimes it will GFS, HDFS class file storage interfaces such non-POSIX interfaces fall into this category.
[] Storage block
Typical devices: disk arrays, disk, virtual hard drive
[file storage]
Typical equipment: FTP, NFS server, SamBa
[object storage]
Typical equipment: built-in high-capacity hard disk distributed servers
Block storage operation target binary data interface, a hard disk physical storage location (directory to find the corresponding logical partition, and then find the corresponding memory block. )
File storage interface operation target is the directories and files , physical storage locations corresponding to the file server by the file system to determine (proportion of a multi-block stored procedure: determining a parameter file which stores the logical directory)
Storage interface operation subject object is the object , a large distributed storage location is a server.
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If the object is a file, using a file server to store (decision parameter file which is stored on the logical directory),
If the object is, the use of block storage
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I think the memory of external services can be divided into two layers,
Layer is the physical layer, the storage layer;
Another layer is the file system layer.
Block storage is to provide services at the physical layer level, the use of its system, useful for its own file system format. Once such a system is used, it is the exclusive.
File storage, file system layer is to provide services, the system can use only one access to the file system, each system can get access based interface.
Providing an object store, a file system service is only optimized to the current file system, using flat manner, abandoned tree structure, easy to share, high-speed access.
Details:
These three storage, corresponding to a different access protocols, which also determines the nature of their differences.
Let me talk about file storage, the main operating target is a file and folder . NFS-for example, documents related interfaces include: LOOKUP / ACCESS / READ / WRITE / CREATE / REMOVE / RENAME , etc., folder-related interfaces include: MKDIR / RMDIR / READDIR and so on. There will also be FSSTAT / FSINFO interfaces for information to provide file system level. POSIX, SAMBA is a file storage and other protocols. Pay more attention to flexible interface protocol, and access control .
Block storage, mainly the operation target disk . With SCSI, for example, the main interface has a Read / Write / Read Capacity / Inquiry, and so on. FC, iSCSI, but also the block storage protocol. And file storage compared to no file and directory tree concept, general agreement does not define the disk creation and deletion. Pay more attention to the transmission control protocol .
Object storage, mainly the operation target object (Object). To S3, for example, the main interface has PUT / GET / DELETE and so on. And compared to stored files and objects, no random access interface. And file storage compared to no tree concept. Pay more attention to simple protocol.