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The old server had canonical problems w.r.t. http/https which is now corrected (on the new server that went live 2 wks ago) and from the looks of things, G is getting things straightened out w.r.t. http/https issues.
Our original plan was to also upgrade our storefront sw when we went live on the new server, but for various reasons we had to delay that upgrade.
We're now ready, but have a concern that all the indexed (albeit many in supplemental) storefront pages will face a 301 rewrite (just one rule, but it will apply to all product pages under the storefront).
Will adding the rewrite as described above be too much of a change for Google and will it trigger some type of penalty? From a site point of view, the % of pages affected by the rewrite is probably 45-50% and on the storefront side we're probably 98-99% (storefront is embedded in the site).
There are many threads here about the potential pitfalls, but if it's done in a technically correct manner the first time, and if you are keeping the same domain name, then this should be a very do-able change. Test your work thoroughly in a bot-protected test environment before going live. Nasty problems can develop with a mis-step and follow-up corrections may take quite a while for Google to untangle.
Also related to your question:
Natural vs. Un-natural - in SEO and the Google Algorithm [webmasterworld.com]
Thanks so much for your suggestions. The link on "URL structure redesign" was great (I do and had used the site search but b.c. the terminology used in my search was not the greatest, I'd missed that important thread!).
And, regarding that thread, I think jdMorgan's approach (#3208327)to doing things in stages makes the most sense and is probably the way we will go.
However, Decius (#3208616) seems to take an almost opposite approach in suggesting
... you should htaccess the site to be ready for the new urls, and then 301 all the old ones to the new ones and hope Google will pick it up ASAP without much of a burp. Anything is is far more risky imo.
Any comments in favor of either approach? Is G capable of dealing with each approach equally well?
I think it covers most of the issues surrounding redirection fairly well.
To answer your question above, I personally do not recommend 'duplicating' you content for any reason, including going from 'unfriendly' to 'friendly'... If you want to make the changes in 'stages' change a directory or two at a time, but all the information I have says it is unnecessary to leave two versions of a page up for any time, and there have been a number of threads on why you do not want to have access to the same content on two URLs.
I usually just rename the page, make sure the links to the old page are all pointing to the new URL, and delete the old page. That's the cleanest transition. Or, sometimes I keep the old URL and re-write the content on the old one so there is no duplication. That works, too.