Persistent L2ARC?

[mattlach]

Hey all,

It never made sense to me that L2ARC residing on SSD's (a mostly stable media) would be wiped on a reboot, and all that optimized cache data would be lost, forcing a rebuild on a drive with finite write cycles.

Sure, servers aren't supposed to reboot often, but still. it happens sometimes.

I did some googling and came across this over at Illumos.

This is not the current behavior of 9.2.1.7 Any idea if this will be added to the FreeBSD ZFS port, and thus (eventually) FreeNAS?

Much Obliged,
Matt

 

[DrKK]

That's so weird. Cyberjock and I were talking about this at length two days ago.

I would ask the guys in #ZFS on irc.

 

[cyberjock]

It's not wiped. That's not the limiting factor. The problem is that the L2ARC index is stored in RAM and on shutdown it's simply discarded. That means on reboot you have to start all over.

No idea as the FreeNAS project guys have no control of when this gets integrated into FreeBSD. If I had to guess I'd say next summer at the earliest.

 

[mattlach]

Interesting. Thank you.

How does the upstream process work on this anyway?

I'd imagine that there is a separate open source ZFS team, since the form from Oracle. Who ports it to BSD? Is it the FreeBSD team, and not the ZFS team?

And who are Illumos? What is their role in all of this? I read the "about us" link on their page, but it didn't give me any clearer of an understanding.

Thanks,
Matt

 

[cyberjock]

First OpenZFs has to write the "generic" ZFS code, then FreeBSD devs implement it, then FreeNAS implements it.

Illumos is just another OS that is designed for ZFS.

 

[mattlach]

Ahh,

Thanks for the info.