2/28/2023 0 Comments Chronosync 2015 cyber mondaySmartScan is a heuristic algorithm which means it produces a result which is good enough most of the time but not necessarily perfect. See the Pitfalls section, below, for a discussion about this. There are also certain types of filesystem activity that can cause SmartScan a little trouble. In such scenarios, the overhead of analyzing the fsEvents database may be so high that it erases any performance gain that SmartScan has to offer (scheduling frequent synchronizations can mitigate this). This can be caused by a very active system (such as a server) or very long periods of time in between syncs. 1,000,000+ file-system modifications) in between synchronizations. SmartScan should also be avoided if your sync set experiences a very high number of changes (e.g. This includes using Boot Camp to run Windows. Important: One not-so-obvious example of moving a volume between systems is if a single computer reboots into different partitions that run different operating systems. If the volume is used on other operating systems, including versions of macOS prior to 10.8, SmartScan should definitely be disabled in the 'Special File/Folder Handling' section of the Sync Document Options Panel. In theory, it will still work but the chance that the fsEvents database on that volume will contain invalid or corrupt information increases when the drive becomes promiscuous. When SmartScan should not be used: If your target volume is transported between machines, you probably should avoid SmartScan. SmartScan may effectively reduce the scanning time but if that time is small relative to how long it takes to copy the files, the net benefit may be negligible. Also, if the amount of data copied is typically very large, you may not see significant performance gains. SmartScan works by telling ChronoSync what parts of your file system it can avoid, so if it can't avoid any of it, there's no performance gain. Also, if your changes are spread out evenly across your sync hierarchy, ChronoSync will still have to access a large portion of your file system. If you're running small syncs (< 100,000 files) and/or have exceptionally fast hardware, you will see minimal performance gains. The worst that will happen is that you might not see dramatic speed benefits. When SmartScan is not-so-good: In general, there is no harm in enabling SmartScan. Such syncs can take hours (or even days) to run but with SmartScan, the time can be reduced to minutes (or maybe just hours). ChronoAgent-based syncs almost always benefit from SmartScan and, the slower the network connection, the greater the performance boost! SmartScan is primarily intended to be used for excessively large syncs that normally take a long time to run due to a very slow analysis pass. When is SmartScan good: When there are a LOT of files to scan, your devices are relatively slow or the connection to those devices (bus or network) is relatively slow - or any combination thereof. If ever there was a "your mileage may vary"-type feature, SmartScan is it! UNDERSTANDING WHEN TO USE IT There are also situations where SmartScan should not be used, so understanding all these factors is important. Or the improvements can be negligible - it all depends on the structure of the file system being scanned and, more important, how those files are used in between syncs. The performance improvements SmartScan offers can be drastic - such as a sync that used to take hours completing in mere minutes. Without the CDE’s file system database as a reference point, the SmartScan algorithm would not be possible. It uses the result of this query as a "hint" for the CDE so it can quickly locate and identify changes that have occurred. ChronoSync queries this database to see what portions of the file system have changed in between runs of a synchronization or backup. It is maintained on a per-volume basis and is quite detailed. The file system events database, or fsEvents for short, contains a record of every file system operation that is performed. SmartScan works by combining the file system events database, maintained by the macOS kernel, with the ChronoSync Difference Engine (CDE), the brains behind every sync and backup that ChronoSync performs. SmartScan is designed to take the pain out of such operations. Add to that the fact that many such operations are performed over a network connection and you get even slower performance. Despite all the advances in computing power over the years, file system traversal is still a relatively slow process. File system analysis can be a time consuming process for many sync and backup operations. SmartScan is an advanced, heuristic algorithm that can greatly reduce the amount of time ChronoSync spends analyzing a pair of file systems for changes. ChronoSync v4.6 introduces a new feature called SmartScan.
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