Query related to ROFS and ZFS performance

[Vikalp Jain]

Hi everyone,

I am new to OSv and unikernel world. The OSv low startup time really intrigued me, so I started doing some experiments. I realize the ROFS file system plays an important role in improving the OSv startup time. This might be a very basic question but I don't understand the reason behind this. It would be really helpful if I can get some pointers on reason performance improvements with ROFS over ZFS.

Thanks in advance. :)

Thanks,

Vikalp Jain

[Fotis Xenakis]

Hello Vikalp,

First of all welcome!

One big differentiating factor of ZFS is its comparatively much more complex and thus longer mount process. See e.g. [1] for a chart comparing mount times on OSv.

More generally, we should bear in mind that ZFS if feature-full and most importantly, it is read-write, whereas ROFS is read-only. This allows it to optimize better for its use case.

Waldek, as the author of ROFS, might have more insight into this.

Fotis

[1] https://github.com/foxeng/diploma/blob/b74692f65039ff5dfdd6f35eb24ae881a3feeca2/img/startup-mount.pdf