FreeBSD + ZFS on a production server?

Daniel Eriksson daniel_k_eriksson at
Thu Jun 12 10:35:25 UTC 2008

Anders Häggström wrote:

> I plan to install a web server for production use and ZFS looks very
> interesting, especially since it has built-in support for RAID and
> checksum.

ZFS is very nice, but slightly over-hyped imho. However, some of the hype is warranted and for some use cases ZFS is a much better fit than UFS.

Despite what Wojciech Puchar says, ZFS checksumming can be very useful. I recently had two drives in a hardware RAID-5 array (8 x 1 TB on a Highpoint RocketRAID 2340) develop unreadable sectors seemingly at the same time. I'm not sure what caused it but the end result was a broken/unavailable array. To make a long story short I managed to get the drives to remap the bad sectors and bring the array back online. Since I had ZFS on the array I didn't have to wait for fsck to run (takes a very long time on a 7 TB array and requires a LOT of memory to even work), and after the pool had been scrubbed I had a list of files with bad checksums that I could restore from backup. With UFS I would have had silent data corruption.

Beware, there have been reports of mmap not working properly together with ZFS. I'm not sure if this is still a problem and if it would affect a typical web server. It does not seem to affect any of my fileservers (exporting NFS).

/Daniel Eriksson

More information about the freebsd-questions mailing list