There are two sets of statistics related to MemDB data striping: MemDB statistics and striping-statistics.
MemDB statistics and striping
MemDB collects statistics under the MemDB-Replicated and MemDB-Local parameter sets, within each data stripe.
They can be monitored on a per-stripe basis, or viewed as an aggregate across all stripes.
The parameter set names of the per-stripe statistics end with suffix of the form .stripe-N.
For example, the stats for the first stripe will have suffix .stripe-0.
Striping statistics
MemDB maintains atomicity, consistency and isolation of data across stripes.
This involves managing the versions of data exposed to various client transactions.
The MemDB-Timestamp parameter set contains the relevant statistics.
This is a listing of the statistics available for a particular MemDB instance, within the MemDB-Timestamp parameter set:
Counter type statistics: Id: Name: Label: Description: 0 waitingThreads waiting The number of threads waiting for a timestamp to become safe 1 unexposedCommits unexposed The number of commits which are not yet safe to expose
A database transaction containing at least one write is considered "safe to expose to client transactions" when (as shown by these statistics) all its changes — as well as all the write transactions that precede them — are available across all stripes.
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These statistics are expected to have low values even under load (often with value zero), and should stay at zero when Rhino is not under load. |
