i found error in logs. server is not responding in this interval aprox. 1~2min.
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Mar 15 22:33:01 matrix kernel: sd 4:0:0:0: [sda] CDB: Test Unit Ready: 00 00 00 00 00 00
Mar 15 22:33:01 matrix kernel: mptbase: ioc0: LogInfo(0x31140000): Originator={PL}, Code={IO Executed}, SubCode(0x0000)...