# Is is possible to run Elasticsearch 6 in a backward compatible mode **URL:** \ **Category:** Elasticsearch\ **Created:** [December 26, 2017, 1:01pm UTC](https://discuss.elastic.co/t/is-is-possible-to-run-elasticsearch-6-in-a-backward-compatible-mode/113211 "2017-12-26T13:01:30Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![pk.241011](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/pk.241011/32/86285_2.png) [@pk.241011](https://discuss.elastic.co/u/pk.241011)\ **Post date:** [December 26, 2017, 1:01pm UTC](https://discuss.elastic.co/t/is-is-possible-to-run-elasticsearch-6-in-a-backward-compatible-mode/113211/1 "2017-12-26T13:01:30Z")
Hi, We recently upgraded the UAT setup (which is also used by the devs) to 6.1. An immediate consequence was that the [Serilog sink for Elasticsearch](https://github.com/serilog/serilog-sinks-elasticsearch) stopped working. From the [details](https://github.com/serilog/serilog-sinks-elasticsearch/issues/140) it seems like it is the string getting replaced by text and \_all support getting dropped proved to be breaking changes for Serilog. So while we wait for the authors to release a patch I have to roll back the cluster to 5.x again. I am pushing my luck but is there a hidden compatibility mode somewhere in Elasticsearch which can allow it to run backward compatible? I am trying to avoid roll back to older version because of new features in Kibana. ---
**Author:** ![dadoonet](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/dadoonet/32/137187_2.png) [@dadoonet](https://discuss.elastic.co/u/dadoonet)\ **Post date:** [December 26, 2017, 5:03pm UTC](https://discuss.elastic.co/t/is-is-possible-to-run-elasticsearch-6-in-a-backward-compatible-mode/113211/2 "2017-12-26T17:03:00Z")
If you create all your indices in a 5.6 cluster, they can be read/write by a 6.x cluster. So may be create a month of indices before upgrading to 6? ---
**Author:** ![shanec](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/shanec/32/4004_2.png) [@shanec](https://discuss.elastic.co/u/shanec)\ **Post date:** [December 26, 2017, 5:08pm UTC](https://discuss.elastic.co/t/is-is-possible-to-run-elasticsearch-6-in-a-backward-compatible-mode/113211/3 "2017-12-26T17:08:17Z")
Unfortunately not. Serilog will need to make any appropriate changes. Just in case you're interested in what these two changes are about: 1. `string` was replaced by `text` back in 5.0 and we did add a "backwards compatibility layer" in at that time and kept it for all of 5.x. There are details about the change [here](https://www.elastic.co/blog/strings-are-dead-long-live-strings). 2. The `_all` change is _only_ for new indices in 6.x. So if you have an index that was created in 5.x, you can upgrade to 6.x and it will continue to work as-is. The second of these may be a workaround for that one if you absolutely need to, but it sounds like Serilog is going to need to make updates regardless of whether the workaround works for one user. Since I'm also not very familiar with the Serilog project and what it provides/suggests, I'll also mention a few other things that could help with your upgrade experience if they're options. One is that if you install X-Pack in 5.x, it comes with [a cluster/index checker](https://www.elastic.co/guide/en/kibana/current/xpack-upgrade-assistant.html) which checks if you're using any features that won't work in 6.x. I realize you may have already run into a few stumbling blocks with your upgrade, but I'd recommend using the utility to check anyway since there may be other things you haven't run into. You should also check the deprecation log for any queries which may need to be upgraded. You can also turn that on with the upgrade assistant if you haven't already. ---
**Author:** ![system](https://us1.discourse-cdn.com/elastic/original/3X/1/a/1ac57faf039f6b580b3f104ef42a2a89e41014de.png) [@system](https://discuss.elastic.co/u/system)\ **Post date:** [January 23, 2018, 5:08pm UTC](https://discuss.elastic.co/t/is-is-possible-to-run-elasticsearch-6-in-a-backward-compatible-mode/113211/4 "2018-01-23T17:08:20Z")
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