Prestools has an extensive experience upgrading and migrating Prestashop and Thirty Bees shops.
Upgrades often go wrong. For that reason Prestools favors upgrading the live shop only when the versions are close to each other and there are no indications of risk. Only in that case the risk that a backup needs to be restored is sufficiently small.
In other situations Prestools' standard approach is to make a copy of your shop in a subdirectory on your server. That copy is upgraded. And then directories are moved to make the upgraded shop the active shop.
The advantage of this approach is that you can take your time to set up the new version. Installing and customizing a new theme or finding a replacement for modules that are not compatible with the new version is no problem. You can also take your time to test everything. When everything is ready the order and product data are once again copied from the old shop so that the new shop is up-to-date when it is made active.
Upgrading the active shop directly is not a serious option as too often that goes wrong. You cannot trust the backup procedure of the upgrade process so you need to make your own backup. And then you have invested almost as much work as when you copy the shop to a subdirectory.
For those who like the do-it-yourself approach Prestools offers the free tools Copy_shopdata and Upgradehub. The latter is specific for Prestashop 1.6. The manual of Copy_shopdata is also a good way to build some understanding of the potential problems that can happen during an upgrade. It gives you also an impression of the expertise of Prestools.
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