Legato Cluster for Linux

Tim Burke burke at missioncriticallinux.com
Wed Apr 5 10:49:32 MDT 2000


Some observations on the Legato product after reading their white papers:

Like so many other cluster "products" they don't address the hard issue of IO Fencing. 
This key feature makes FailSafe a much stronger offering.   Seems like the strength of
this product is its cross platform capabilities. 

Some key excerpts from the white papers:

Cluster supports multiple networks but does not require them. .... recommended that you
configure each cluster to have at least 2 private networks to eliminate it as a SPOF...

This tidbit was very well buried deep into one whitepaper:
"If only one network is used and a network partition occurs between the machines accessing
the disk, communication is lost and there are no checks to ensure that only one machine
accesses the disk at one time.  Disk corruption may occur due to concurrent writes.  The
addtion of redundant networks greatly reduces the risk of this secenario."

...

"Cluster manages access to the storage device, helping to ensure that concurrent access
does not corrupt data.  However, Cluster does not control disk operations or provide any
access restrictions.  Permissions and restrictions are controlled by the underlying
operating system or filesystem."



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