Recording Speed with Multiple vbOnline Devices
QUESTION
How many vbOnline devices can I connect together, yet still maintain performance?
ANSWER
Using Ethernet networking it is physically possible to connect very large numbers of vbOnline devices and run them on one database and with one Online Manager. Network traffic is not a problem for a typical 100Mbps network.
For installations which do not use QuickScan, the performance limitation will be the processing power of the server PC which runs Online Manager and the database. This PC must schedule the recordings, check alarms and save data to the database. A typical 3GHz P4 server PC can process 1000 recordings per hour, leading to the guidelines in the table below.
For installations which use QuickScan, a complete QuickScan of all channels is performed between each scheduled recording. The QuickScan recording time dominates and limits the scheduled recordings to a Medium work load of 1 per channel per hour (assuming all 32 channels are in use, with accelerometer sensors). Because the server's processing requirements for QuickScan are very light, the system performs equally well with several vbOnline devices at that Medium work load.
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Recommended max number of 32-channel vbOnlines per Online Manager & database |
Scheduled Recordings Only |
QuickScan & Scheduled Recordings |
|
Heavy work load (10 recordings per channel per hour) |
3 |
- |
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Medium work load (1 recording per channel per hour) |
30 |
5 |
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Light workload (6 recordings per channel per 24hr day) |
120 |
40 |
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Notes:
These guidelines are based upon the following assumptions:
- The PC is using a 3GHz Pentium 4 CPU or equivalent.
- All 32 channels are being used on all vbOnline devices.
- Two 16-channel devices load the system slightly more than a single 32 channel device.
- Recordings are assumed to be typically Fmax=1kHz, 4 averages, 400 lines.
Another factor to consider is database size. Each recording above will add approximately 2 KB to the database. Therefore, 10 vbOnline devices running at the medium work load for a month will add 460 MB. To maintain responsive behavior of Ascent we recommend that the database be kept below 1 GB. Data Thinning should be used to thin out the older recordings. This process can be automated in Online Manager. A database Backup followed by a Restore will free up the space created by the data thinning.
If either the recording performance or database size recommendations above are likely to impact your installation, we recommend that the database be divided in two, with each on its own PC, and each with their own Online Manager.
FAQ ID: 19250 Last Reviewed: 9 March 2007