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Block IO Testing / Measurement / Benchmarking Suite for large Projects, with Real-Life Loads. See wiki.


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blkreplay is a GPL’ed toolkit, driving the block
layer of Linux (or other Unix-like OSes) while measuring
latency and throughput of IO operations for later visualization
(so-called “sonar diagrams” and others).

In addition to artificial loads like random read-write sweeps
and various kinds of overload tests, blkreplay can replay
**natural loads** which have been recorded by blktrace (or
Windows DiskMon) at heavily-loaded production servers
at big data centers.

blkreplay comes with a **large collection of natural loads**
from a wide spectrum of applications (such as web servers,
databases, dedicated servers, etc) which have been released
to the public by 1&1 under GPL.


Some of these natural loads have recorded the real-life
disk access behaviour from servers serving thousands of
customers in parallel.

Static analysis of the workingset behaviour of such natural
loads is also implemented.

blkreplay comes with a modular and extensible **test suite**,
automating large projects for testing and/or benchmarking.

blkreplay can be used to test physical hardware, e.g. compare
different brands of hard disks, or RAID controllers / their
settings / RAID rebuild performance degradation, or to
evaluate the effect of SSD caching, or to compare different
block level transports like iSCSI vs Fibrechannel (over
different kinds of storage networks).

It can compare virtual hardware (like vmware or XenServer
block devices, or any type of block-level storage
virtualization) to each other or to physical hardware,
provided the test setup is handled very carefully.

blkreplay can compare commercial storage boxes from vendors
like EMC, NetApp, IBM, Hitachi, etc to each other or to
cheap off-the-shelf hardware (in order to determine the
price/performance ratio), provided the test setup is also
handled very carefully.

Furthermore, it can be used for tests of the Linux kernel,
e.g. for testing device drivers, comparing different IO
schedulers at different load patterns, determining the
overhead of Linux dm targets, determining the impact of
network problems to DRBD, and much more.

At 1&1, blkreplay has even been used as a tool for
root cause analysis of incidents: for example, high
load peaks presumably stemming from traffic jam (or other
sources of overload) were recorded at production
sites in real time by blktrace, and later replayed
in the laboratory (without causing customer impact)
seeking for the cause of trouble, or improving the
safety margins by choice of better hardware.

For experts in IO subsystems, visualization techniques like
“sonar diagrams” can reveal (parts of) the internal structure
of complex IO systems, such as cache hierarchies or other
hierarchical storage systems.

As a community project under GPL, blkreplay is open to
contributions from hardware vendors, other data centers,
the kernel hacker community, etc.


Full documentation:


Database of loads:


Block IO Testing / Measurement / Benchmarking Suite for large Projects, with Real-Life Loads. See wiki.