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Ask the Experts
Question:
I want go storage as a career...i did SCSA recently and want to go for
storage, can you receommand any basic and advanced books or classes
available in pune (Maharashtra). I will really appreciate that.
Submitter: Mangesh
Date: 11/13/08
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Expert Answers:
Yes, SNIA Education has an extensive portfolio of tutorials. The best
place for him to start is http://www.snia-india.org/ and
http://www.snia-india.org/SNIA%20Tutorials.html
Expert: Giri
A great resources is SNIA’s recently released Storage Networking Skills
Self-Assessment. It’s a 45-question test that you can take online for
free, and at the end of the test, there is a very helpful section on
preparing for the various SNIA certification exams. There is a 12-slide
bibliography as well.
Just point your browser to http://www.snia.org/education/certification/practice/index.htm
Expert: Rick
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Question: I am thinking
of a design to improve performance of SAN. To do this I am thinking of
an in band switch based virtualization which recieves an ISCSI request
and splits the request into two and simultaneously reads data from two
insync disk at remote locations. tell me is this solution feasible!!
And I want software based solution with minimum hardware involvement!
Tell me how out of band storage virtualization can help me in this?
Submitter: Varun
Date: 8/26/2008 |
Expert Answer: Varun,
I believe you are talking about splitting a SCSI (encapsulated in
iSCSI) READ or WRITE request and execute them simultaneously on two
mirrored disks at remote locations. The solution is feasible, but to
see if this solution improves performance we need to consider multiple
scenarios. SCSI read write requests are based on logical block
addresses (LBA). i.e A request consists of number of bytes to
read/write starting from a given LBA. If the request can be serviced by
reading or writing from a single spindle (a logical unit can have
extents on multiple spindles depending on the RAID level), there may
not be huge performance benefit by splitting a SCSI request. If the
iSCSI switch can determine the SCSI request may require data from more
than one spindle ( or sets of spindles), it is possible to realize some
performance benefit by splitting the original request… a through
characterization needs to be performed to gauge the performance. It is
also possible to design algorithms that will intelligently direct a
series of SCSI requests to multiple mirrored locations. This method
will work best for the random work loads and again the performance
depends on the latency in accessing a remote mirror image.
Expert: Giri Basava
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