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1. #HFS FILE SYSTEM FAULT TOLERANT FEATURES UPDATE#
2. #HFS FILE SYSTEM FAULT TOLERANT FEATURES FULL#
3. #HFS FILE SYSTEM FAULT TOLERANT FEATURES SOFTWARE#
4. #HFS FILE SYSTEM FAULT TOLERANT FEATURES CODE#
5. #HFS FILE SYSTEM FAULT TOLERANT FEATURES OFFLINE#

An ODBC/ JDBC connect string can specify a list of alternate server instances thus as long as the application is written to try to reconnect as best practices dictate, there is no new code needed.įor the deadlock, the application is supposed to retry the transaction.

#HFS FILE SYSTEM FAULT TOLERANT FEATURES OFFLINE#

There are two types of errors that can occur in any database application: The database server instance may be offline or otherwise unreachable and a transaction may be aborted due to a deadlock.įor the missing server instance, the application should try to reconnect.

#HFS FILE SYSTEM FAULT TOLERANT FEATURES FULL#

Application Developers/ProgrammersĪn application can connect to any server instance in the cluster and have access to the same data, with full ACID properties. Mirrored disks will shorten the vulnerability window of running a partition on a single server instance since this will for the most part eliminate the need to copy many (hundreds) of GB of database files when recovering a failed instance. Having mirrored disks in individual hosts is optional since data will anyhow be in two copies. The system is online in read-write mode during all this time, including during copying. Finally start the replacement database, and the system will do the rest.

If the disks are gone, then copy the database files from the live copy. If the disks are OK, put the old disks in the replacement host and start.

Reboots and the like are handled without operator intervention if there is a broken host, then remove it and put a spare in its place. When things break, as long as there is at least one server instance up from each quorum, things will continue to work. Use two switches, and two NICs per machine, and connect one of each server's network cables to each switch, to cover switch failures. It is enough for tables and indices to specify partitioning. Table definitions do not have to be altered for fault tolerance. These things are declared in a configuration file. To configure, divide your server instances into quorums of 2 or 3, according to which will be mirrors of each other, with each quorum member on a different host from the others in its quorum. Again, please contact us if you have a specific case in mind. Running multiple sites in parallel is also possible but specifics will depend on the application. Details will vary please contact us for specifics.

#HFS FILE SYSTEM FAULT TOLERANT FEATURES UPDATE#

Using an off-site backup plus update stream, one can reconstitute the failed data center on a cloud provider in a few hours. The most basic site-wide disaster recovery plan consists of constantly streaming updates off-site.

#HFS FILE SYSTEM FAULT TOLERANT FEATURES SOFTWARE#

This does not protect against widespread power outage or the building burning down the scope is limited to hardware and software failures at one site. Server instances are grouped in "quorums" of two or, for extra safety, three as long as one member of each quorum is available, the system keeps running and nobody sees a difference, except maybe for slower response. You do not end up paying for unused capacity.

Since most applications are about reading, this is a good deal. In reality, the cost is less since you get the whole money's worth of read throughput and half the money's worth of write throughput. The cost is in purchasing twice (or thrice) the hardware and software licenses. The value gained is elimination of downtime. I will explain the matter to each of these three groups: Executives Application Developers/Programmers: Will I need to write extra code? Can old applications get fault tolerance with no changes?.System Administrators: Is it hard to configure? What do I do when I get an alert?.Executives: What does it cost? Will it really eliminate downtime?.Three types of individuals need to know about fault tolerance: I will follow up with technical specifics in another post. So I will here make a few high level statements about what we offer for fault tolerance. The gist of the matter is that failure and recovery processes have been automated so that neither application developer nor operating personnel needs any knowledge of how things actually work. (This feature is not in and is not planned to be added to the Open Source Edition.)īased on some feedback from the field, we decided to make this feature more user friendly. We have for some time had the option of storing data in a cluster in multiple copies, in the Commercial Edition of Virtuoso. Font-family: Arial, Helvetica, sans-serif īackground: #0075A8 url("/ods/images/navlv1default.png")}Ĭolor: #fff /* Required due to buggy CSS in IE */}īackground: #b1d4e5 url("/ods/images/navlv1sel.png")}īackground: #ddeff9 url("/ods/images/navlv2default.png")}Ĭolor: #444 /* Required by buggy IE CSS implementation */ }