BitKeeper - The Scalable Distributed Software Configuration Management System

"BitKeeper is the only product on the market place that meets our needs for an easy to use SCM tool that allows us to work when the network goes down, to trivially reorganize our source base, and easily get all the information about the change over time of our source code." -- Pawel S. Veselov, Sun Microsystems Inc.

ClearCase is integrated into the operating system as a file system. Experience has shown that this can be problematic each time the operating system is upgraded.
ClearCase is slow for many common operations when compared against a local filesystem.
ClearCase is quite resource hungry - it is not uncommon to spend as much as $300,000 for a large SMP server to serve up 20 developers. An inexpensive PC can do the same job with BitKeeper.
ClearCase is expensive in more ways than just seat costs. The hardware and administrative costs to run a ClearCase server can dwarf the seat costs. It is common to allocate a full time administrator to manage the ClearCase server and software.
The ClearCase multisite feature is an attempt to decentralize a centralized system and it doesn't work as well as a truly distributed system. The basic idea is that each site gets a branch, that branch is writable by that site only, the other site's branches are read only. BitKeeper has no such restrictions, all sites can work on the same branch at the same time.
BitKeeper improves debugging efficiency of developers through changesets; it is trivial to go from a line of code to the changeset which introduced that line.
Development managers can perform better code reviews with BitKeeper.
Management can easily track project progress through the BK/Web interface.
BitKeeper is easier for administrative staff to learn and support.
BitKeeper is more reliable - all repositories are database replicas.
BitKeeper allows full-development efficiency at remote sites, with no loss of performance or functionality.
BitKeeper saves money through dramatically reduced hardware requirements.
BitKeeper is fast - maintains single user performance levels.
Summary: ClearCase is the mature market leader, but has a centralized architecture which implies many limitations. BitKeeper has a proven distributed, replicated architecture without those same limitations. Total cost of ownership with ClearCase can easily exceed 5 times that of BitKeeper for the same development effort.

BitKeeper/ClearCase Feature Comparison Matrix

Download BitKeeper/ClearCase Feature Comparison matrix (pdf)

Feature	BK/Pro	ClearCase	Benefit
Atomic ChangeSets	Yes	No	Every change is a reproducible snap shot Aids in debugging and release management
Graphical checkin tool	Yes	Yes	Graphical tool for file and changeset checkins which promotes more useful comments to speed up development processes and debugging
Dynamic branching	Yes	No	Any workspace can be turned into a branch Advanced planning for branching is unneeded
Pro Merge Technology	Yes	No	Most accurate automerge available Only merge each change once
Accurate handling of renames	Yes	Yes	Increased productivity through a well organized source base
Peer-to-peer architecture	Yes	No	Supports any workflow for enhanced quality control Supports the rapid open source style of development
Complete local history	Yes	No	Your developers can keep working even when your server or network doesn't Inherent reliability through replication
True parallel development	Yes, trivial	Yes, complex	Enhanced productivity Faster time to market
Multi-site development	Yes, included	Yes, add on	BitKeeper provides 100% functionality and productivity at all distributed sites ClearCase's add on is a high cost, high admin band-aid to decentralize a centralized system
Mobile/Off-network functionality	Yes	No	Increased development productivity by allowing your developers to work while traveling, while at remote locations, while at customer sites, or without a network
Dynamic Licensing	Yes	No	Provides developers the flexibility of checking in from any host or domain Read-only users can access data without tying up a license Developers never have to wait for a license to become available
Pre-event triggers	Yes	Yes	Ability to qualify events prior to changes which enhances compliance to your development policies
Post-event triggers	Yes	Yes	Supports notification of events and automated secondary operations which provides easier process management
Replicated repositories	Yes	Limited, with multisite	Provides enhanced reliability along with the ability to perform transparent, automatic backups ClearCase provides a multi site add on which does replicate the repository data, but with a very high admin overhead
Automatic integrity checks	Yes	No	Detects corruptions indicating potential hardware and software problems saving time and money associated with unplanned downtime
Accurate recording of all history	Yes	No	Accountability: Easy to find Who did What When Provides a complete picture of your parallel development Speeds up debugging process
Minimal Administration	Yes	No	Convert at least one headcount from every development site from administrator to developer Saves the cost of one full time admin at every development site
Minimal hardware requirements	Yes	No	No need to purchase additional hardware No requirement for large, expensive server

ClearCase is a trademark of Rational Software Corporation.

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