Thursday, July 25, 2013

Technical overview of OneFS continued

OneFS manages protection of its data directly by allocating data during normal operations and rebuilding data after recovery.  It does not rely on hardware RAID levels. OneFS determines which files are affected by a failure in constant time. Files are repaired in parallel. As the cluster size increases, their resiliency increases.
Systems that use a "hot spare" drive, use it to replace a failed drive.  OneFS avoids the use of hot spare drives and instead uses available free space to recover from failure. This is referred to as virtual hot spare and guarantees that the system can self-heal.
Data protection is applied at the file level and not the system level, enabling the system to focus on only those files affected by failure. Reed Solomon error codes are used for data but metadata and inodes are protected by mirroring only.
Further the data protection is configurable and can be appliedy dynamically and online. For a file protection involving N data blocks protected by M error code blocks and b file stripes, the protection level is (N + M ) / b, When b = 1, M members can fail simultaneously and still provide 100% availability.As opposed to the double failure protection of RAID-6, this system can provide upto quadruple failure protection.
OneFS also does automatic partitioning of nodes to improve Mean Time to Data Loss (MTTDL). If a 80 node cluster at +4 protection level is partitioned into four twenty node pools at +2, then the protection overhead is reduced, space is better utilized and there is no net addition to management overhead.
Automatic provisioning subdivides the nodes into pools of twenty nodes each and six drives per node. Furthermore, the node's disks are now subdivided into multiple, separately protected poolsand they are significantly more resilient to multiple disk failures than previously possible.
Supported protocols for client access to create, modify and read data include the following:
NFS Network file system used for unix/linux based computers
SMB/CIFS (server message block and Common Internet File System)
FTP : File Transfer Protocol
HTTP : Hypertext Transfer Protocol
iSCSI : Internet Small Computer System Interface
HDFS: Hadoop distributed file system
REST API : Representational state transfer Application Programming Interface.
By default only the SMB/CIFS and NFS are enabled. The root system for all file data is ifs Isilon OneFS file system. The SMB/CIFS protocol has an ifs share and the NFS has an /ifs export.
Changes made by one protocol is visible to all others because the file data is common.

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