Slow transfer speed through Samba using software RAID

I have a mini PC (Intel Celeron J4005, 4GB RAM, Intel Gigabit NIC), configured with: - Ubuntu (5.4.0-81-generic, installed on sda) - Samba (version 4.11.6-Ubuntu) - FTP (vsftpd, no encryption) - RAID5 (mdadm, md0: sdb-sdc-sdd, USB-SATA) The RAID array is shared via Samba and FTP, but I want to eliminate FTP, all major clients are Windows machines. The problem is that I get way slower speeds through Samba share than FTP: | Device | Method | Read Speed (Mbyte/s, one large file) | |-| -|-| | md0 | local | ~220 | | md0 | LAN, FTP | ~115 (network limit) | | md0 | LAN, Samba | ~48 | | md0 | LAN, Samba, second run (cached in memory) | ~115 (network limit) | | sda | LAN, Samba | ~115 (network limit) | I tried with default Samba settings and with the current one (attached below), but I got the same result. I flushed the cache between tests. iostat output sample (LAN, Samba, first run): Device r/s rkB/s rrqm/s %rrqm r_await rareq-sz w/s wkB/s wrqm/s %wrqm w_await wareq-sz d/s dkB/s drqm/s %drqm d_await dareq-sz aqu-sz %util md0 793.00 433408.00 0.00 0.00 0.00 546.54 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 sda 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 sdb 254.00 16768.00 8.00 3.05 14.74 66.02 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 3.27 84.80 sdc 171.00 16896.00 93.00 35.23 2.99 98.81 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.32 60.80 sdd 161.00 16640.00 101.00 38.55 11.74 103.35 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 1.57 96.00 iostat output sample (LAN, FTP, first run): Device r/s rkB/s rrqm/s %rrqm r_await rareq-sz w/s wkB/s wrqm/s %wrqm w_await wareq-sz d/s dkB/s drqm/s %drqm d_await dareq-sz aqu-sz %util md0 1828.00 292480.00 0.00 0.00 0.00 160.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 sda 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 sdb 458.00 39040.00 153.00 25.04 1.66 85.24 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.18 75.60 sdc 457.00 38976.00 152.00 24.96 1.45 85.29 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.09 70.40 sdd 457.00 38976.00 152.00 24.96 1.59 85.29 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.15 75.20 I have no clue what the problem can be, can someone help me, or at least where I should start investigating? ---------- Samba config: [global] workgroup = WORKGROUP min protocol = SMB3 log level = 1 socket options = TCP_NODELAY SO_RCVBUF=65536 SO_SNDBUF=65536 IPTOS_LOWDELAY SO_KEEPALIVE use sendfile = true aio read size = 65536 aio write size = 65536 read raw = yes write raw = yes getwd cache = yes acl allow execute always = true log file = /var/log/samba/log.%m max log size = 1000 logging = file server role = standalone server obey pam restrictions = yes unix password sync = yes passwd program = /usr/bin/passwd %u passwd chat = *Enter\snew\s*\spassword:* %n\n *Retype\snew\s*\spassword:* %n\n *password\supdated\ssuccessfully* . pam password change = yes map to guest = bad user [Share] path = /media/hdd writable = yes valid users = myuser directory mode = 0770 create mode = 0660 RAID array configuration: /dev/md0: Version : 1.2 Creation Time : Tue Sep 7 13:19:26 2021 Raid Level : raid5 Array Size : 976441344 (931.21 GiB 999.88 GB) Used Dev Size : 488220672 (465.60 GiB 499.94 GB) Raid Devices : 3 Total Devices : 3 Persistence : Superblock is persistent Intent Bitmap : Internal Update Time : Tue Sep 9 14:37:52 2021 State : clean Active Devices : 3 Working Devices : 3 Failed Devices : 0 Spare Devices : 0 Layout : left-symmetric Chunk Size : 64K Consistency Policy : bitmap Filesystem info: root@MiniPC:~# df -h Filesystem Size Used Avail Use% Mounted on udev 1.8G 0 1.8G 0% /dev tmpfs 371M 12M 360M 3% /run /dev/sda2 58G 3.4G 55G 6% / tmpfs 1.9G 12K 1.9G 1% /dev/shm tmpfs 5.0M 0 5.0M 0% /run/lock tmpfs 1.9G 0 1.9G 0% /sys/fs/cgroup tmpfs 500M 79M 422M 16% /var/cache/apt tmpfs 500M 0 500M 0% /tmp tmpfs 500M 0 500M 0% /var/backups tmpfs 500M 2.2M 498M 1% /var/log tmpfs 500M 0 500M 0% /var/tmp /dev/sda1 511M 5.3M 506M 2% /boot/efi /dev/md0 917G 356G 562G 39% /media/hdd root@MiniPC:~# lsblk NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT sda 8:0 0 59.6G 0 disk ├─sda1 8:1 0 512M 0 part /boot/efi └─sda2 8:2 0 59.1G 0 part / sdb 8:16 0 465.7G 0 disk └─sdb1 8:17 0 465.7G 0 part └─md0 9:0 0 931.2G 0 raid5 /media/hdd sdc 8:32 0 465.8G 0 disk └─sdc1 8:33 0 465.8G 0 part └─md0 9:0 0 931.2G 0 raid5 /media/hdd sdd 8:48 0 465.8G 0 disk └─sdd1 8:49 0 465.8G 0 part └─md0 9:0 0 931.2G 0 raid5 /media/hdd