Last updated 1-11-2022
If you are using a Raspberry Pi 4B for your piserver, you will want to have faster, larger, and more reliable storage for your clients. The Pi 4B model has USB 3.0 ports for connecting to external storage and it has a gigabit network port for your clients to PXE boot from and store data on this storage over the NFS configured by piserver.

Speed comparison from this test suite by others:
sudo curl https://raw.githubusercontent.com/TheRemote/PiBenchmarks/master/Storage.sh | sudo bash
description: 32 GB EVO select (green) microSD Samsung - Model: GB1QT - Vendor: SM - Product: SD - HW Version: 0x3 - FW Version: 0x0 - Date Manufactured: 11/2018 - Class: Class 10 U1 Category Test Result HDParm Disk Read 41.20 MB/s HDParm Cached Disk Read 40.65 MB/s DD Disk Write 10.7 MB/s FIO 4k random read 3309 IOPS (13238 KB/s) FIO 4k random write 208 IOPS (835 KB/s) IOZone 4k read 10368 KB/s IOZone 4k write 3901 KB/s IOZone 4k random read 10278 KB/s IOZone 4k random write 2545 KB/s Score: 1071
description: Benfei USB 3.0 to Sata II adapter (ID 2537:1068 ) with UASP & Western Digital model: ATA WDC WDS250G2B0A size: 232.89 GiB Category Test Result HDParm Disk Read 184.10 MB/s HDParm Cached Disk Read 183.72 MB/s DD Disk Write 159 MB/s FIO 4k random read 3264 IOPS (13059 KB/s) FIO 4k random write 4884 IOPS (19537 KB/s) IOZone 4k read 22151 KB/s IOZone 4k write 18547 KB/s IOZone 4k random read 16217 KB/s IOZone 4k random write 22724 KB/s Score: 5575