Thank you for all suggestions. I have HDD drive. Bellow are the results from commnads.
Also I realised that I had very quick response from commands bellow but I was doing this in administrator user. But bitcoin-cli is running under another user. So if I run getblockchaininfo it still needs around 10 seconds for response.
$ ps aux | sort -nrk 3,3
bitcoin 615 53.2 63.7 1072472 605576 ? Ssl Mar31 9523:59 /usr/local/bin /bitcoind -daemon -conf=/home/bitcoin/.bitcoin/bitcoin.conf -pid=/home/bitcoin/. bitcoin/bitcoind.pid
admin 17785 4.0 0.4 6308 4232 pts/0 Ss 21:00 0:00 -bash
admin 17772 1.1 0.5 9656 5104 ? Ss 21:00 0:00 /lib/systemd/sy stemd --user
root 85 0.8 0.0 0 0 ? D Mar31 155:48 [usb-storage]
root 17768 0.5 0.5 11632 5528 ? Ss 21:00 0:00 sshd: admin [pr iv]
root 8 0.2 0.0 0 0 ? I Mar31 37:26 [rcu_sched]
root 44 0.2 0.0 0 0 ? S Mar31 39:06 [kswapd0]
root 7 0.1 0.0 0 0 ? S Mar31 32:16 [ksoftirqd/0]
USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND
systemd+ 335 0.0 0.0 17276 432 ? Ssl Mar31 0:05 /lib/systemd/sy stemd-timesyncd
root 91 0.0 0.2 35116 2384 ? Ss Mar31 0:32 /lib/systemd/sy stemd-journald
root 9 0.0 0.0 0 0 ? I Mar31 0:00 [rcu_bh]
root 90 0.0 0.0 0 0 ? I< Mar31 0:03 [kworker/2:1H]
root 86 0.0 0.0 0 0 ? S Mar31 0:00 [irq/169-usb-00 1]
root 84 0.0 0.0 0 0 ? I< Mar31 0:00 [scsi_tmf_0]
root 83 0.0 0.0 0 0 ? S Mar31 0:00 [scsi_eh_0]
root 71 0.0 0.0 0 0 ? I< Mar31 0:00 [ipv6_addrconf]
root 70 0.0 0.0 0 0 ? I< Mar31 0:00 [ext4-rsv-conve r]
root 69 0.0 0.0 0 0 ? S Mar31 0:04 [jbd2/mmcblk0p2 -]
root 68 0.0 0.0 0 0 ? S Mar31 17:15 [mmcqd/0]
root 64 0.0 0.0 0 0 ? S Mar31 0:00 [irq/92-mmc1]
root 63 0.0 0.0 0 0 ? S< Mar31 0:00 [SMIO]
root 62 0.0 0.0 0 0 ? S Mar31 0:00 [vchiq-keep/0]
root 61 0.0 0.0 0 0 ? S< Mar31 0:00 [vchiq-sync/0]
root 6 0.0 0.0 0 0 ? I< Mar31 0:00 [mm_percpu_wq]
root 60 0.0 0.0 0 0 ? S< Mar31 0:00 [vchiq-recy/0]
root 596 0.0 0.6 47228 5800 ? Sl Mar31 6:21 /usr/bin/python 3 /usr/bin/fail2ban-server -s /var/run/fail2ban/fail2ban.sock -p /var/run/fail2b an/fail2ban.pid -x -b
root 590 0.0 0.0 4184 0 tty1 Ss+ Mar31 0:00 /sbin/agetty -- noclear tty1 linux
root 59 0.0 0.0 0 0 ? S< Mar31 0:00 [vchiq-slot/0]
root 58 0.0 0.0 0 0 ? I< Mar31 0:00 [DWC Notificati o]
root 575 0.0 0.0 2936 388 ? Ss Mar31 0:12 /sbin/dhcpcd -q -w
root 57 0.0 0.0 0 0 ? I< Mar31 0:00 [dwc_otg]
root 56 0.0 0.0 0 0 ? I< Mar31 0:00 [iscsi_eh]
root 55 0.0 0.0 0 0 ? I< Mar31 0:00 [kthrotld]
root 517 0.0 0.0 7072 0 ? Ss Mar31 0:00 /usr/lib/blueto oth/bluetoothd
root 513 0.0 0.0 2084 0 ? S Mar31 0:00 /usr/bin/hciatt ach /dev/serial1 bcm43xx 3000000 flow - b8:27:eb:bd:25:6b
root 512 0.0 0.0 0 0 ? I< Mar31 0:00 [kworker/u9:1]
root 511 0.0 0.0 0 0 ? I< Mar31 0:00 [kworker/u9:0]
root 483 0.0 0.0 10024 212 ? Ss Mar31 0:18 wpa_supplicant -B -c/etc/wpa_supplicant/wpa_supplicant.conf -iwlan0 -Dnl80211,wext
root 45 0.0 0.0 0 0 ? I< Mar31 0:00 [nfsiod]
root 41 0.0 0.0 0 0 ? I< Mar31 0:00 [xprtiod]
root 4 0.0 0.0 0 0 ? I< Mar31 0:00 [kworker/0:0H]
root 40 0.0 0.0 0 0 ? I< Mar31 0:00 [rpciod]
root 395 0.0 0.0 23756 596 ? Ssl Mar31 0:14 /usr/sbin/rsysl ogd -n
root 39 0.0 0.0 0 0 ? I< Mar31 0:00 [watchdogd]
root 380 0.0 0.0 5292 272 ? Ss Mar31 0:05 /usr/sbin/cron -f
root 38 0.0 0.0 0 0 ? I< Mar31 0:00 [kblockd]
root 377 0.0 0.2 7412 2048 ? Ss Mar31 0:05 /lib/systemd/sy stemd-logind
root 37 0.0 0.0 0 0 ? I< Mar31 0:00 [crypto]
root 36 0.0 0.0 0 0 ? S Mar31 1:29 [kcompactd0]
root 35 0.0 0.0 0 0 ? I< Mar31 0:00 [writeback]
root 34 0.0 0.0 0 0 ? S Mar31 0:00 [oom_reaper]
root 33 0.0 0.0 0 0 ? S Mar31 0:01 [khungtaskd]
root 309 0.0 0.0 0 0 ? I< Mar31 0:00 [ext4-rsv-conve r]
root 308 0.0 0.0 0 0 ? S Mar31 1:34 [jbd2/sda1-8]
root 307 0.0 0.0 0 0 ? I< Mar31 0:06 [kworker/0:1H]
root 305 0.0 0.0 0 0 ? I< Mar31 0:02 [kworker/3:1H]
root 28 0.0 0.0 0 0 ? I< Mar31 0:00 [netns]
root 27 0.0 0.0 0 0 ? S Mar31 0:00 [kdevtmpfs]
root 26 0.0 0.0 0 0 ? I< Mar31 0:00 [kworker/3:0H]
root 24 0.0 0.0 0 0 ? S Mar31 3:20 [ksoftirqd/3]
root 236 0.0 0.0 0 0 ? S Mar31 0:00 [brcmf_wdog/mmc 1]
root 234 0.0 0.0 0 0 ? I< Mar31 0:00 [brcmf_wq/mmc1: 0]
root 23 0.0 0.0 0 0 ? S Mar31 0:00 [migration/3]
root 228 0.0 0.0 0 0 ? I< Mar31 0:00 [cfg80211]
root 22 0.0 0.0 0 0 ? S Mar31 0:00 [cpuhp/3]
root 21 0.0 0.0 0 0 ? I< Mar31 0:00 [kworker/2:0H]
root 2 0.0 0.0 0 0 ? S Mar31 0:01 [kthreadd]
root 19 0.0 0.0 0 0 ? S Mar31 5:43 [ksoftirqd/2]
root 18 0.0 0.0 0 0 ? S Mar31 0:00 [migration/2]
root 17767 0.0 0.0 0 0 ? I 20:58 0:00 [kworker/2:1]
root 17766 0.0 0.0 0 0 ? I 20:57 0:00 [kworker/0:2]
root 17765 0.0 0.0 0 0 ? I 20:56 0:00 [kworker/1:1]
root 17764 0.0 0.0 0 0 ? I 20:52 0:00 [kworker/2:2]
root 17763 0.0 0.0 0 0 ? I 20:52 0:00 [kworker/0:1]
root 17762 0.0 0.0 0 0 ? I 20:50 0:00 [kworker/1:0]
root 17759 0.0 0.0 0 0 ? I 20:44 0:00 [kworker/1:2]
root 17758 0.0 0.0 0 0 ? I 20:41 0:00 [kworker/2:0]
root 17752 0.0 0.0 0 0 ? I 20:31 0:00 [kworker/3:1]
root 17749 0.0 0.0 0 0 ? I 20:28 0:00 [kworker/0:0]
root 17748 0.0 0.0 0 0 ? I 20:26 0:00 [kworker/u8:2]
root 17715 0.0 0.0 0 0 ? I 19:48 0:00 [kworker/3:2]
root 17676 0.0 0.0 0 0 ? I 19:03 0:01 [kworker/u8:0]
root 17 0.0 0.0 0 0 ? S Mar31 0:00 [cpuhp/2]
root 16366 0.0 0.0 10200 544 ? Ss Apr11 0:00 /usr/sbin/sshd -D
root 16259 0.0 0.1 39704 1840 ? Ssl Apr11 0:00 /usr/lib/policy kit-1/polkitd --no-debug
root 16 0.0 0.0 0 0 ? I< Mar31 0:00 [kworker/1:0H]
root 147 0.0 0.0 0 0 ? I< Mar31 0:03 [kworker/1:1H]
root 14 0.0 0.0 0 0 ? S Mar31 4:42 [ksoftirqd/1]
root 137 0.0 0.0 14480 264 ? Ss Mar31 0:04 /lib/systemd/sy stemd-udevd
root 13 0.0 0.0 0 0 ? S Mar31 0:00 [migration/1]
root 12 0.0 0.0 0 0 ? S Mar31 0:00 [cpuhp/1]
root 11 0.0 0.0 0 0 ? S Mar31 0:00 [cpuhp/0]
root 1 0.0 0.4 28032 3836 ? Ss Mar31 0:24 /sbin/init
root 10 0.0 0.0 0 0 ? S Mar31 0:00 [migration/0]
nobody 376 0.0 0.0 5292 148 ? Ss Mar31 0:10 /usr/sbin/thd - -triggers /etc/triggerhappy/triggers.d/ --socket /run/thd.socket --user nobody - -deviceglob /dev/input/event*
message+ 382 0.0 0.1 6504 1044 ? Ss Mar31 0:01 /usr/bin/dbus-d aemon --system --address=systemd: --nofork --nopidfile --systemd-activation
avahi 426 0.0 0.0 6392 0 ? S Mar31 0:00 avahi-daemon: c hroot helper
avahi 403 0.0 0.0 6392 556 ? Ss Mar31 1:13 avahi-daemon: r unning [MariborBitcoinLN.local]
admin 17808 0.0 0.0 9964 460 pts/0 S+ 21:00 0:00 sort -nrk 3,3
admin 17807 0.0 0.2 7736 2840 pts/0 R+ 21:00 0:00 ps aux
admin 17782 0.0 0.3 11632 3356 ? S 21:00 0:00 sshd: admin@pts /0
admin 17775 0.0 0.1 29696 984 ? S 21:00 0:00 (sd-pam)
$ free -m
total used free shared buff/cache available
Mem: 927 628 31 1 267 246
Swap: 1873 351 1522
$ iostat -d -x
Linux 4.14.98-v7+ (MyBitcoinNode) 12/04/19 _armv7l_ (4 CPU)
Device: rrqm/s wrqm/s r/s w/s rkB/s wkB/s avgrq-sz avgqu-sz await r_await w_await svctm % util
mmcblk0 1.68 2.49 8.09 6.10 51.51 34.38 12.11 3.80 267.83 11.75 607.76 6.65 9.43
sda 0.37 1.05 76.57 2.60 880.34 227.23 27.98 1.12 14.12 11.25 98.78 10.32 8