Quite clearly, this is bonkers.
If you block access from search engine spiders how can they possibly index the content in good faith? You are hoping that they will not crawl the content to check what is there (or burn server resources) but they will still happily refer users of their search engine to these pages in good faith.
Additionally, it is highly unlikely that bots from the major engines are causing a measurable impact - Google for instance states they will only crawl one page every few seconds (1).
That said, there are a lot of parasites out there and crawlers that will eat up server time so there may also be some truth in what the host is saying. That said, there is still no excuse for this hatchet job of sorting things out.
The other angle here is that magento and ecommerce sites can often be a crawlers worst nightmare. As an example product comparison systems can often create thousands (I have seen millions) of crawlable URLs - now a sensible spider has a crawl budget and will give up but that's not saying all will. A simple crawl in screaming frog should give you an idea here (not that you will be able to do that) and in many cases where these problems exist this is enough to bring a server to it's knees.
In my mind you have a few things to do here
1. Convince the host that blocking all spiders is incorrect
Hopefully this thread and the references here should be more than enough to do this. Beyond that simply show them a fetch as Googlebot & the Crawl section in webmaster tools and you should be able to make your point quickly and easily.
2. Help the developer implement a more sensible list of what to block.
This article is a good start here:
http://searchenginewatch.com/article/2067357/Bye-bye-Crawler-Blocking-the-Parasites
Remember you can allow one (or more) robots and then disallow everything else:
User-agent: Google
Disallow:
User-agent: *
Disallow: /
Other options also exist such as limiting the speed at which a crawler can crawl - well, requesting that they limit the speed at which they crawl.
Also remember that any truly parasitic bot or crawler will likely ignore robots.txt anyway so you may need to implement some more advanced blocking at a firewall or server level.
3. Help the developer identify the cause of the resources problem
As hinted at above, if a crawl is causing problems there are likely issues somewhere. Whether this is as simple as straight up server resources or is more due to problems with the site and crawlable URLs needs to be determined but let me give you some pointers.
- SEO Audit - at least a crawl / indexation audit - lets see how many pages we can crawl? How does this stack up against the amount of products / categories? You may well find some easy wins here and sections of the site that can be blocked off or variables you tell Google not to crawl in webmaster tools. Nofollow directives and URLs can be your friend here as well so you tackle it on both fronts.
- Magento Optimisation - it is easy with a system like Magento to create pages that have a heavy burden on the database with hundreds of queries. If these options are not really used (only by crawlers) then they can be audited and removed / improved.
- Server Resources - Magento can be a hungry beast
- Dig into the http access logs to identify who and what is crawling and from where and come up with a list of what you need to block and how.
Summary
Ultimately, blocking all spiders is daft and there is a good chance it won't resolve the issue anyway - that is unless it screws over the clients search visibility so badly that they don't do any traffic! There are likely issues though be that with the site itself or something else so a good way to couch this to them is as their friend and helper - someone who will help them identify and resolve the issues. If it gets combative then it will only be harder to resolve.
Alternatively, you could move to another host. Part of me would suggest doing this anyway as no host should be able to hold you to ransom like this. This one daft move could have potentially ruined the clients visibility in what is a key time of the year for most online businesses. Imagine if they did not have an SEO on board? If they did not have an automated crawl to highlight these issues?
There is certainly a worthwhile exercise here as the site likely has some problems (or at least areas that can be improved upon) so optimisations can be made but, I would still consider jumping ship and moving to an SEO savvy host in the long term if bridges can't be built.
Hope that helps!
Marcus
References
- https://support.google.com/webmasters/answer/182072?hl=en
- http://searchenginewatch.com/article/2067357/Bye-bye-Crawler-Blocking-the-Parasites
- http://www.robotstxt.org/