Mariadb server down

[/details]

Nextcloud version (eg, 20.0.5): 21.0.5.1
Operating system and version (eg, Ubuntu 20.04): Dietpi (Debian Buster) PHP version _(eg, 7.4)_: root@DietPi:/# php --version
PHP 7.3.29-1~deb10u1 (cli) (built: Jul 2 2021 04:04:33) ( NTS )
Copyright (c) 1997-2018 The PHP Group
Zend Engine v3.3.29, Copyright (c) 1998-2018 Zend Technologies
with Zend OPcache v7.3.29-1~deb10u1, Copyright (c) 1999-2018, by Zend Technologies`

Is this the first time you’ve seen this error? (Y/N): YES

Hello, I use Nextcloud server on Dietpi (Debian Buster miniPC Intel x64). I have internal server errors few time and after reboot everything works fine. I try tu upgrade to Bullseye but on https I have error 503 service unavailable and on http address I have www site without internet.
I decide to restore system backup to have my Nextcloud working. Restoring went fine but after reboot system was down. I have to restore grub. After that system is working and all services are OK but not Mariadb. I cannot run Nextcloud.


dietpi@DietPi:~$ sudo dietpi-services status

 DietPi-Services
─────────────────────────────────────────────────────
 Mode: status                                                           [  OK  ] DietPi-Services | avahi-daemon         active (running) since Fri 2021-10-08 14:02:29 CEST; 8h ago
[  OK  ] DietPi-Services | proftpd              active (running) since Fri 2021-10-08 14:02:29 CEST; 8h ago
[  OK  ] DietPi-Services | nfs-kernel-server    active (exited) since Fri 2021-10-08 14:02:29 CEST; 8h ago
[  OK  ] DietPi-Services | redis-server         active (running) since Fri 2021-10-08 14:02:29 CEST; 8h ago
[FAILED] DietPi-Services | ● mariadb.service - MariaDB 10.3.29 database server
   Loaded: loaded (/lib/systemd/system/mariadb.service; disabled; vendor preset: enabled)
   Active: failed (Result: exit-code) since Fri 2021-10-08 20:00:34 CEST; 2h 3min ago
     Docs: man:mysqld(8)
           https://mariadb.com/kb/en/library/systemd/
  Process: 8185 ExecStartPre=/usr/bin/install -m 755 -o mysql -g root -d /var/run/mysqld (code=exited, status=0/SUCCESS)
  Process: 8186 ExecStartPre=/bin/sh -c systemctl unset-environment _WSREP_START_POSITION (code=exited, status=0/SUCCESS)
  Process: 8188 ExecStartPre=/bin/sh -c [ ! -e /usr/bin/galera_recovery ] && VAR= ||   VAR=`cd /usr/bin/..; /usr/bin/galera_recovery`; [ $? -eq 0 ]   && systemctl set-environment _WSREP_START_POSITION=$VAR || exit 1 (code=exited, status=0/SUCCESS)
  Process: 8245 ExecStart=/usr/sbin/mysqld $MYSQLD_OPTS $_WSREP_NEW_CLUSTER $_WSREP_START_POSITION (code=exited, status=1/FAILURE)
 Main PID: 8245 (code=exited, status=1/FAILURE)
   Status: "MariaDB server is down"

Oct 08 20:00:32 DietPi systemd[1]: Starting MariaDB 10.3.29 database server...
Oct 08 20:00:33 DietPi mysqld[8245]: 2021-10-08 20:00:33 0 [Note] /usr/sbin/mysqld (mysqld 10.3.29-MariaDB-0+deb10u1) starting as process 8245 ...
Oct 08 20:00:34 DietPi systemd[1]: mariadb.service: Main process exited, code=exited, status=1/FAILURE
Oct 08 20:00:34 DietPi systemd[1]: mariadb.service: Failed with result 'exit-code'.
Oct 08 20:00:34 DietPi systemd[1]: Failed to start MariaDB 10.3.29 database server.
[  OK  ] DietPi-Services | php7.3-fpm           active (running) since Fri 2021-10-08 14:02:31 CEST; 8h ago
[  OK  ] DietPi-Services | lighttpd             active (running) since Fri 2021-10-08 14:02:31 CEST; 8h ago
[  OK  ] DietPi-Services | emby-server          active (running) since Fri 2021-10-08 14:02:31 CEST; 8h ago
[  OK  ] DietPi-Services | noip2                active (running) since Fri 2021-10-08 14:02:31 CEST; 8h ago
[  OK  ] DietPi-Services | cron                 active (running) since Fri 2021-10-08 14:02:31 CEST; 8h ago
[  OK  ] DietPi-Services | ssh                  active (running) since Fri 2021-10-08 14:02:29 CEST; 8h ago
[  OK  ] DietPi-Services | fail2ban             active (running) since Fri 2021-10-08 14:02:13 CEST; 8h ago
[ INFO ] DietPi-Services | dietpi-vpn           inactive (dead)
[  OK  ] DietPi-Services | dietpi-ramlog        active (exited) since Fri 2021-10-08 14:02:13 CEST; 8h ago
[  OK  ] DietPi-Services | dietpi-preboot       active (exited) since Fri 2021-10-08 14:02:13 CEST; 8h ago
[  OK  ] DietPi-Services | dietpi-boot          active (exited) since Fri 2021-10-08 14:02:29 CEST; 8h ago
[  OK  ] DietPi-Services | dietpi-postboot      active (exited) since Fri 2021-10-08 14:02:29 CEST; 8h ago
[ INFO ] DietPi-Services | dietpi-wifi-monitor  inactive (dead)
root@DietPi:/var/www/nextcloud/config# cat config.php
<?php
$CONFIG = array (
  'passwordsalt' => 'xxxxxxxxxxxxxxxxxxxx/Fa',
  'secret' => 'GxxxxxxxxxxxxxxxxxxxxxVo',
  'trusted_domains' =>
  array (
    0 => 'localhost',
    1 => '*',
  ),
  'datadirectory' => '/mnt/dietpi_userdata/nextcloud_data',
  'dbtype' => 'mysql',
  'version' => '21.0.5.1',
  'hashingThreads' => 4,
  'memcache.local' => '\\OC\\Memcache\\APCu',
  'filelocking.enabled' => true,
  'memcache.locking' => '\\OC\\Memcache\\Redis',
  'redis' =>
  array (
    'host' => '/run/redis/redis-server.sock',
    'port' => 0,
  ),
  'overwrite.cli.url' => 'http://localhost/nextcloud',
  'dbname' => 'nextcloud',
  'dbhost' => 'localhost',
  'dbport' => '',
  'dbtableprefix' => 'oc_',
  'mysql.utf8mb4' => true,
  'dbuser' => 'oc_admin',
  'dbpassword' => 'xxxxxxxxxxxxxxxxxD',
  'installed' => true,
  'instanceid' => 'oxxxxxxxxxxy',
  'maintenance' => true,
  'twofactor_enforced' => 'true',
  'twofactor_enforced_groups' =>
  array (
  ),
  'twofactor_enforced_excluded_groups' =>
  array (
  ),
  'loglevel' => 2,
  'theme' => '',
);
dietpi@DietPi:~$ sudo cat /var/log/mysql/error.log
2021-10-08 15:41:49 0 [Note] InnoDB: Using Linux native AIO
2021-10-08 15:41:49 0 [Note] InnoDB: Mutexes and rw_locks use GCC atomic builtins
2021-10-08 15:41:49 0 [Note] InnoDB: Uses event mutexes
2021-10-08 15:41:49 0 [Note] InnoDB: Compressed tables use zlib 1.2.11
2021-10-08 15:41:49 0 [Note] InnoDB: Number of pools: 1
2021-10-08 15:41:49 0 [Note] InnoDB: Using SSE2 crc32 instructions
2021-10-08 15:41:49 0 [Note] InnoDB: Initializing buffer pool, total size = 128M, instances = 1, chunk size = 128M
2021-10-08 15:41:49 0 [Note] InnoDB: Completed initialization of buffer pool
2021-10-08 15:41:49 0 [Note] InnoDB: If the mysqld execution user is authorized, page cleaner thread priority can be changed. See the man page of setpriority().
2021-10-08 15:41:49 0 [ERROR] InnoDB: Unsupported redo log format. The redo log was created with MariaDB 10.5.11.
2021-10-08 15:41:49 0 [ERROR] InnoDB: Plugin initialization aborted with error Generic error
2021-10-08 15:41:50 0 [Note] InnoDB: Starting shutdown...
2021-10-08 15:41:50 0 [ERROR] Plugin 'InnoDB' init function returned error.
2021-10-08 15:41:50 0 [ERROR] Plugin 'InnoDB' registration as a STORAGE ENGINE failed.
2021-10-08 15:41:50 0 [Note] Plugin 'FEEDBACK' is disabled.
2021-10-08 15:41:50 0 [ERROR] Unknown/unsupported storage engine: InnoDB
2021-10-08 15:41:50 0 [ERROR] Aborting

dietpi@DietPi:~$ sudo readlink /var/lib/mysql
/mnt/dietpi_userdata/mysql
dietpi@DietPi:~$ sudo readlink -f /var/lib/mysql
/mnt/Toshiba/dietpi_userdata/mysql
dietpi@DietPi:~$ 

Please help me.
Regards,
Przemek.