Fix doc about max number of failing zone

[ilmiye]

The doc related to maximum number of failing zone to operate is wrong.

You say that the system can tolerate failures as long as the number of failing zones is fewer than floor(replication_factor / 2). For example:

Replication Factor = 3 => floor(3 / 2) = 1 > max-num-of-failing-zone => max-num-of-failing-zone = 0

However, we know that Mimir can tolerate 1 zone loss when RF=3.

I updated the doc to give number of healthy zone instead of number of maximum failing zone to operate.

[CLAassistant]

All committers have signed the CLA.

[56quarters]

Thank you, this is much clearer!

[ilmiye]

Also, the doc says Deploying Grafana Mimir clusters to more zones than the configured replication factor does not have a negative impact. but it does not mention what would be the benefits of deploying more Mimir zone than RF.

In addition, to have a section which mentions read path implications of number-of-mimir-zone > RF situation would be very beneficial. Like how Querier selects the ingesters with related data since not all data exists in all zones now.

[56quarters]

Also, the doc says Deploying Grafana Mimir clusters to more zones than the configured replication factor does not have a negative impact. but it does not mention what would be the benefits of deploying more Mimir zone than RF.

In addition, to have a section which mentions read path implications of number-of-mimir-zone > RF situation would be very beneficial. Like how Querier selects the ingesters with related data since not all data exists in all zones now.

Opened #9513 to keep track of those improvements after merging this PR.