[quote="hossein_ey, post:12, topic:85733"]
so in this situation data completely lost ?

No. Not completely. Some shards might be missing. Not all.

[quote="hossein_ey, post:12, topic:85733"]
we can not restore that ?

It depends but it might be hard to recover from that situation. Depending on how the RED actually occurred.

[quote="hossein_ey, post:12, topic:85733"]
what is your recommendation? do we use elasticsearch as a primary database or we use another database

The one I already pasted:

> Some customers use Elasticsearch as a primary datastore, some set-up comprehensive back-up solutions using features such as our Snapshot and Restore, while others use Elasticsearch in conjunction with a data storage system like Hadoop or even flat files. Elasticsearch can be used for so many different use cases which is why we have created this page to make sure you are fully informed when you are architecting your system.

So it really depends on your case. IMO you have 3 options:

* You absolutely don't care about loosing part of your data. Let say "non critical logs". Then, may be you will loose 1 day of data at some point but may be it's not that critical for you and actually don't worth adding another server for storing
* You absolutely care about your data and you want to be able to reindex in all cases. You need for that a datastore. A datastore can be a filesystem where you store JSON, HDFS, and/or a database you prefer and you are confident with. About how to inject data in it, you may want to read: http://david.pilato.fr/blog/2015/05/09/advanced-search-for-your-legacy-application/.
* Well. You know that you can loose data in some extreme corner cases but you don't want to pay the price of other servers. Do backups, use elasticsearch replicas (increase to 2)... But you know the risk.
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