Post by @subnetspider@mastodon.bsd.cafe

@subnetspider@mastodon.bsd.cafe

2026-09-17 17:08 UTC

I always find it funny when someone on the Internet says "ZFS is memory hungry" or "ZFS needs at least 8 GB of ECC RAM to run". Nonsense. To prove it, I installed #FreeBSD 15.1 (64 bit!) on a 23 year old PC, with ZFS and only 1 GB of RAM, running multiple jails without issue. 😎 It has been a bit tricky to get FreeBSD 15.1 to boot off a modern SATA drive, but I found some old PCI SATA controller I bought way back in the Windows 7 days which is still supported. The single core AMD Athlon 64 3000+ is a bit slow, but pkgbase really helps with speeding up installing patches. It's still fast enough to reach 604 Mbit/s in iperf3 (and 490 Mbit/s in client mode). If I wanted to, I could even turn this ancient machine into a NAS, which really proves that old PCs aren't trash, but modern software is.

Replies (4)

@mroach@ublog.mroach.com 2026-09-17 17:36

@subnetspider@mastodon.bsd.cafe ZFS is memory hungry the same way System Idle Process is CPU hungry :p Love this project! Modern software really is such trash.

Open ##4741799
@subnetspider@mastodon.bsd.cafe 2026-09-17 17:32

The image quality isn't great, but here are some pictures of the physical machine:

Open ##5077192
@charlesrocket@defcon.social 2026-09-17 17:13

@subnetspider@mastodon.bsd.cafe what about sata to usb-c? i boot penguins that way via external ssd

Open ##5077193
@david_chisnall@infosec.exchange 2026-09-18 19:12

@subnetspider@mastodon.bsd.cafe The first port of ZFS to FreeBSD was memory hungry because the buffer cache and ARC both held copies of pages. Every page being accessed used two pages, one in ARC and one in the buffer cache. Around FreeBSD 9ish, the buffer cache was extended to be able to handle pages that it didn’t own, which removed that overhead. ZFS does need a bit more cache than UFS for good performance. The bit that’s still true is that dedup needs a lot of RAM. ZFS needs to probe the dedup tables on each store when dedup is enabled, which means performance rapidly drops off if you start missing on probes.

Open ##5077197