VDiskLoad

Generates a write-only load on the VDisk. Simulates a Distributed Storage Proxy. The test outputs the VDisk write performance in operations per second.

Actor parameters

The basic actor parameters are described below. For the full list of parameters, see the load_test.proto file in the YDB Git repository.

Parameter	Description
VDiskId	Parameters of the VDisk used to generate load. GroupID: Group ID. GroupGeneration: Group generation. Ring: Group ring ID. Domain: Ring fail domain ID. VDisk: Index of the VDisk in the fail domain.
GroupInfo	Description of the group hosting the loaded VDisk (of the appropriate generation).
TabletId	ID of the tablet that generates the load. It must be unique for each load actor.
Channel	ID of the channel inside the tablet that will be specified in the BLOB write and garbage collection commands.
DurationSeconds	The total test time in seconds; when it expires, the load stops automatically.
WriteIntervals	Setting up the parameters for probabilistic distribution of intervals between the records.
WriteSizes	Size of the data to write. It is selected randomly for each request from the Min-Max range. You can set multiple WriteSizes ranges, in which case a value from a specific range will be selected based on its Weight.
InFlightPutsMax	Maximum number of concurrent BLOB write queries against the VDisk (TEvVPut queries); if omitted, the number of queries is unlimited.
InFlightPutBytesMax	Maximum number of bytes in the concurrent BLOB write queries against the VDisk (TEvVPut-requests).
PutHandleClass	Class of data writes to the disk subsystem. If the TabletLog value is set, the write operation has the highest priority.
BarrierAdvanceIntervals	Setting up the parameters for probabilistic distribution of intervals between the advance of the garbage collection barrier and the write step.
StepDistance	Distance between the currently written step Gen:Step of the BLOB and its currently collected step. The higher is the value, the more data is stored. Data is written from Step = X and deleted from all the BLOBs where Step = X - StepDistance. The Step is periodically incremented by one (with the BarrierAdvanceIntervals period).

Parameters of probabilistic distribution

An interval written as a repeated TIntervalInfo field is calculated by the following algorithm:

• An element from the TIntervalInfo array is selected at random with the probability proportionate to its weight.
• For an element of the TIntervalUniform type, the value is chosen with equal probability in the range Min-Max. Min-Max (if MinMs/MaxMs is used, the value is in milliseconds; if MinUs/MaxUs is used, the value is in microseconds).
• For an element of the TIntervalPoisson type, the interval is selected using the formula Min(log(-x / Frequency), MaxIntervalMs), where x is a random value in the interval [0, 1]. As a result, the intervals follow the Poisson distribution with the given Frequency, but with the interval within MaxIntervalMs.

A similar approach is used for the probabilistic distribution of the size of the written data. However, in this case, only the data size follows a uniform probability distribution, within the interval [Min, Max].