[Yandex Cloud documentation](../../index.md) > [Yandex Managed Service for Apache Kafka®](../index.md) > FAQ

# General questions about Managed Service for Apache Kafka®

* [How do I achieve high cluster availability?](#cluster-fault-tolerance)

* [What should I do if I get this or similar error: "disk size must be at least ... according to topics partitions number and replication factor, but size is ..."?](#disk-size)

* [How do I get the logs of my activity in the Yandex Cloud services?](#logs)

* [How longs are logs retained?](#log-keeping)

* [How do I move a cluster to a different network?](#move-cluster)

* [How do I set up an alert that triggers as soon as a certain percentage of disk space is used up?](#disk-space-percentage)

* [Why is my cluster slow even though the computing resources are not fully utilized?](#throttling)

* [Can I connect to cluster hosts over SSH or get superuser privileges on hosts?](#connect-ssh)

* [What should I do if I get a revocation check error when using PowerShell to obtain an SSL certificate?](#get-ssl-error)

* [Can I manage a cluster using scripts from an Apache Kafka® distribution?](#script-apache-kafka)

* [What should I do if the _kafkacat: command not found_ error occurs?](#kafkacat-not-found)

* [What do I do if I get an authentication error when connecting via kafkacat?](#kafkacat-authentication-error)

* [Will Karapace be available during maintenance?](#karapace-maintenance)

* [Is Karapace's endpoint constant or does it vary depending on the broker?](#karapace-endpoint)

* [What is the role of Managed Service for Apache Kafka® in database management and maintenance?](#services)

* [How do I track message loss in an Apache Kafka® topic?](#lost-messages)

* [What block size is used on the cluster disks?](#block-size)

* [Which MirrorMaker connector version is supported by Managed Service for Apache Kafka®?](#mirrormaker-version)

#### How do I achieve high cluster availability? {#cluster-fault-tolerance}

Make sure it complies with all the [high availability conditions](../concepts/ha-cluster.md).

#### What should I do if I get this or similar error: "disk size must be at least ... according to topics partitions number and replication factor, but size is ..."? {#disk-size}

This error occurs because the log segments of your topics use more space than the broker storage can provide. For more information about calculating the required space, see [Minimum storage size](../concepts/storage.md#minimal-storage-size).

To solve this issue, you can [increase the disk storage size](../operations/cluster-update.md#change-disk-size) for the [entire cluster](../operations/cluster-update.md#change-kafka-settings) or reduce the [topic](../operations/cluster-topics.md#update-topic) segment size.

#### Can I get logs of my operations in Yandex Cloud? {#logs}

Yes, you can request information about operations with your resources from Yandex Cloud logs. Do it by contacting [support](https://center.yandex.cloud/support).

#### What is the retention period for logs? {#log-keeping}

Cluster logs are stored for 45 days.

#### How do I move a cluster to a different network? {#move-cluster}

You cannot move a Managed Service for Apache Kafka® cluster to different network.


Here is an alternative solution:

1. Create a new cluster with the same configuration in the target network.
1. Use [MirrorMaker](../tutorials/kafka-connectors.md#kf-mirrormaker) to move the topics of your source cluster to the new cluster.


#### How can I configure an alert for when disk usage reaches a certain percentage? {#disk-space-percentage}

[Create an alert](../operations/monitoring.md#monitoring-integration) for the `disk.used_bytes` metric in Yandex Monitoring. This metric shows the disk space usage in the Managed Service for Apache Kafka® cluster.

For `disk.used_bytes`, use notification thresholds with the following recommended values:

* `Alarm`: 90% of disk space
* `Warning`: 80% of disk space

Thresholds are set in bytes only. For example, the recommended values for a 100 GB disk are as follows:

* `Alarm`: `96636764160` bytes (90%)
* `Warning`: `85899345920` bytes (80%)

#### Why is my cluster slow even though the computing resources are not fully utilized? {#throttling}

Your storage may have insufficient maximum [IOPS and bandwidth](../../compute/concepts/storage-read-write.md) to process the current number of requests. In this case, [throttling](../../compute/concepts/storage-read-write.md#throttling) occurs, which degrades the entire cluster performance.

The maximum IOPS and bandwidth values increase by a fixed value when the storage size increases by a certain step. The step and increment values depend on the disk type:

| Disk type                  | Step, GB | Max IOPS increase (read/write) | Max bandwidth increase (read/write), MB/s |
|-----------------------------|---------|------------------------------------|-----------------------------------------------|
| `network-hdd`               | 256     | 300/300                            | 30/30                                         |
| `network-ssd`               | 32      | 1,000/1,000                          | 15/15                                         |
| `network-ssd-nonreplicated`, `network-ssd-io-m3` | 93      | 28,000/5,600                         | 110/82                                        |

To increase the maximum IOPS and bandwidth values and make throttling less likely, [expand the storage](../operations/storage-space.md#change-disk-size).

#### Can I connect to cluster hosts over SSH or get superuser privileges on hosts? {#connect-ssh}

You cannot connect to hosts via SSH. This is done for the sake of security and user cluster fault tolerance because direct changes inside a host can render it completely inoperable.

#### What should I do if I get a revocation check error when obtaining an SSL certificate via PowerShell? {#get-ssl-error}

Complete error message:

```text
curl: (35) schannel: next InitializeSecurityContext failed: Unknown error (0x80092012)
The revocation function was unable to check revocation for the certificate
```
This means that, when connecting to the website, the function was unable to check if its certificate was listed as revoked.

To fix this error:

* Make sure your corporate network policies are not blocking the verification.
* Run the following command with `--ssl-no-revoke`:

   ```powershell
   mkdir $HOME\.kafka; curl.exe --ssl-no-revoke -o $HOME\.kafka\YandexInternalRootCA.crt https://storage.yandexcloud.net/cloud-certs/CA.pem
   ```

#### Can I manage a cluster using scripts from an Apache Kafka® distribution? {#script-apache-kafka}

Yes, you can, but with some limitations.

For more information about the API types available in a cluster and applicable limitations, see [APIs in Managed Service for Apache Kafka®](../concepts/available-apis.md).

For an example of using scripts, see [Connecting to an Apache Kafka® cluster from applications](../operations/connect/clients.md).

#### What should I do if the _kafkacat: command not found_ error occurs? {#kafkacat-not-found}

On Ubuntu 24.04 and higher, use `kcat` instead of `kafkacat` (this command will not work).

#### What do I do if I get an authentication error when connecting via kafkacat? {#kafkacat-authentication-error}

Error message:

```text
SASL authentication error: Authentication failed during authentication due to invalid credentials with SASL mechanism SCRAM-SHA-512
```

This error occurs when you attempt to connect via `kafkacat` to a cluster with Apache Kafka® version 4.0 or higher. `kafkacat` is deprecated and incompatible with new versions. If your cluster runs Apache Kafka® version 4.0 or higher, use [kafkactl](../operations/connect/clients.md#kafkactl) instead.

#### Will Karapace be available during maintenance? {#karapace-maintenance}

[Karapace](https://github.com/Aiven-Open/karapace) is unavailable during maintenance and automatically restarts after its completion. Meanwhile, all schema data is retained as it is stored in the `__schema_registry` [service topic](../concepts/topics.md#service-topics).

#### Is Karapace's endpoint constant or does it vary depending on the broker? {#karapace-endpoint}

Karapace is deployed on each broker host on a separate port, with its own endpoint available for connection. When you delete a broker, the associated endpoint becomes unavailable.

#### What is the role of Managed Service for Apache Kafka® in database management and maintenance? {#services}

Be mindful of what is managed by the service and what, by the Yandex Cloud customer. Understanding these zones of control makes you an efficient user of cloud resources and helps avoid potential database-related issues. For more information, see [Zones of control between managed database (MDB) service users and Yandex Cloud](../../overview/concepts/mdb-responsibilities.md).

#### How do I track message loss in an Apache Kafka® topic? {#lost-messages}

If a topic uses the `Delete` log cleanup policy with a short segment lifetime, messages may be deleted before the [consumer group](../concepts/producers-consumers.md#consumer-groups) reads them. You can monitor message loss using Managed Service for Apache Kafka® [metrics](../metrics.md) delivered to [Monitoring](../../monitoring/concepts/index.md).

To monitor message loss:

1. Use [Yandex Monitoring](https://monitoring.yandex.cloud) to [plot](../../monitoring/operations/metric/metric-explorer.md#add-graph) the `kafka_group_topic_partition_offset` and `kafka_log_Log_LogStartOffset` metrics on the same chart:
   * For `kafka_group_topic_partition_offset`, specify these labels:
       * `service = managed-kafka`
       * `name = kafka_group_topic_partition_offset`
       * `host = <host_FQDN>`
       * `topic = <topic_name>`
       * `partition = <partition_number>`
       * `group = <consumer_group_name>`
   * For `kafka_log_Log_LogStartOffset`, specify these labels: 
       * `service = managed-kafka`
       * `name = kafka_log_Log_LogStartOffset`
       * `host = <host_FQDN>`
       * `topic = <topic_name>`
       * `partition = <partition_number>`
1. Wait until the number of messages written to the topic is enough for analysis.
1. Navigate to [Yandex Monitoring](https://monitoring.yandex.cloud) and review the behavior of the previously created metrics:
   * If the `kafka_log_Log_LogStartOffset` value is higher than `kafka_group_topic_partition_offset` within the entire monitoring period, the selected consumer group will have enough time to read all new messages from the specified topic segment.
   * `kafka_group_topic_partition_offset` falling below `kafka_log_Log_LogStartOffset` signals a message loss.

For more information, see [Monitoring message loss in an Apache Kafka® topic](../tutorials/retention-policy.md).

#### What block size is used on the cluster disks? {#block-size}

[Block](https://en.wikipedia.org/wiki/Block_(data_storage)) size for all disk types is 4 KB.

#### Which MirrorMaker connector version is supported by Managed Service for Apache Kafka®? {#mirrormaker-version}

Managed Service for Apache Kafka® supports **MirrorMaker** version 2.