It's a circular buffer. When the buffer is filled up the oldest stuff in it is overwritten with new stuff. You setup the circular buffers for your needs. Typically you want high resolution data only for items in the recent past and lower resolution data for times previous... so you setup your buffers that way.
If you want the highest resolution data for every unit of time from now until eternity you probably should look for another solution... General circular buffer: http://en.wikipedia.org/wiki/Circular_buffer quick overview of RRD as a concept http://en.wikipedia.org/wiki/RRDtool From: rrd-users-bounces+dshriver=mitre....@lists.oetiker.ch [mailto:rrd-users-bounces+dshriver=mitre....@lists.oetiker.ch] On Behalf Of Kaushal Shriyan Sent: Wednesday, October 02, 2013 1:24 PM To: rrd-users@lists.oetiker.ch Subject: [rrd-users] Overwrites existing data Hi, As per the URL http://oss.oetiker.ch/rrdtool/tut/rrd-beginners.en.html I am not sure i understand about In case of linear databases, new data gets appended at the bottom of the database table. Thus its size keeps on increasing, whereas the size of an RRDtool database is determined at creation time. Imagine an RRDtool database as the perimeter of a circle. Data is added along the perimeter. When new data reaches the starting point, it overwrites existing data. This way, the size of an RRDtool database always remains constant. The name "Round Robin" stems from this behavior. "When new data reaches the starting point, it overwrites existing data" Does it mean the existing data is lost? so how do i keep track of the historical data if it overwrites? Please help me understand with examples. Regards, Kaushal
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