ReadyNAS 214 very slow to write, even locally from USB. (20MB/s)

I have printed my partition table in case that helps...? I read that to be 4k aligned the start *and* end sectors had to be divisble by 8, but the end sector isn't. Not sure if that's correct in this instance. I'm a pretty confident commandline user but I don't know much about disk partitioning which is why I'm here.

root@red-queen:~# fdisk -l

Disk /dev/mtdblock0: 1.8 MiB, 1835008 bytes, 3584 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk /dev/mtdblock1: 256 KiB, 262144 bytes, 512 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk /dev/mtdblock2: 6 MiB, 6291456 bytes, 12288 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk /dev/mtdblock3: 4 MiB, 4194304 bytes, 8192 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk /dev/mtdblock4: 100 MiB, 104857600 bytes, 204800 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk /dev/mtdblock5: 128 KiB, 131072 bytes, 256 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk /dev/mtdblock6: 16 MiB, 16777216 bytes, 32768 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk /dev/sda: 3.7 TiB, 4000787030016 bytes, 7814037168 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disklabel type: gpt
Disk identifier: 5234781B-725A-4CC3-852F-063A26950DA8

Device       Start        End    Sectors  Size Type
/dev/sda1       64    8388671    8388608    4G Linux RAID
/dev/sda2  8388672    9437247    1048576  512M Linux RAID
/dev/sda3  9437248 7814037119 7804599872  3.6T Linux RAID

Disk /dev/sdb: 3.7 TiB, 4000787030016 bytes, 7814037168 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disklabel type: gpt
Disk identifier: 38E77CF2-A96F-4DCD-8964-5A5C75649AE4

Device       Start        End    Sectors  Size Type
/dev/sdb1       64    8388671    8388608    4G Linux RAID
/dev/sdb2  8388672    9437247    1048576  512M Linux RAID
/dev/sdb3  9437248 7814037119 7804599872  3.6T Linux RAID

Disk /dev/sdc: 5.5 TiB, 6001175126016 bytes, 11721045168 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disklabel type: gpt
Disk identifier: E2073793-2307-48A1-92C0-483EE50EE1C1

Device       Start        End    Sectors  Size Type
/dev/sdc1       64    8388671    8388608    4G Linux RAID
/dev/sdc2  8388672    9437247    1048576  512M Linux RAID
/dev/sdc3  9437248 7814037119 7804599872  3.6T Linux RAID

Disk /dev/sdd: 5.5 TiB, 6001175126016 bytes, 11721045168 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disklabel type: gpt
Disk identifier: 681B3DF7-48A4-4056-97A1-C4FEEEAA309A

Device       Start        End    Sectors  Size Type
/dev/sdd1       64    8388671    8388608    4G Linux RAID
/dev/sdd2  8388672    9437247    1048576  512M Linux RAID
/dev/sdd3  9437248 7814037119 7804599872  3.6T Linux RAID

Disk /dev/md0: 4 GiB, 4290772992 bytes, 8380416 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disk /dev/md1: 1020 MiB, 1069547520 bytes, 2088960 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 524288 bytes / 1048576 bytes
Disk /dev/md127: 14.5 TiB, 15983279341568 bytes, 31217342464 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 65536 bytes / 262144 bytes
Disk /dev/sde: 57.8 GiB, 61991813632 bytes, 121077761 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0xb5eac6c6

Device     Boot     Start       End   Sectors  Size Id Type
/dev/sde1  *         2048 121012223 121010176 57.7G  7 HPFS/NTFS/exFAT
/dev/sde2       121012224 121077759     65536   32M ef EFI (FAT-12/16/32)

Disk /dev/sdf: 14.5 GiB, 15581839360 bytes, 30433280 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x0034be61

Device     Boot Start      End  Sectors  Size Id Type
/dev/sdf1  *       64 30433279 30433216 14.5G  c W95 FAT32 (LBA)