Stux
MVP
- Joined
- Jun 2, 2016
- Messages
- 4,419
Found this post, where someone is reporting FreeNAS crashing on heavy data transfers, the crash happens after it starts swapping... unnecessarily... perhaps... which is the calling card of this ARC/VM/UMA conflict
https://forums.freenas.org/index.php?threads/freenas-crashing-on-heavy-data-transfers.41851/
Someone points out the FreeBSD bug thread I've been trawling
@jgreco even drops in to wonder if this is part of the infamous bug 1531, Performance Suckage
https://bugs.freenas.org/issues/1531
I understand that Bug 1531 is actually because the write buffers get overloaded...
Anywho, I'll trawl through the FreeNAS bug tracker
https://forums.freenas.org/index.php?threads/freenas-crashing-on-heavy-data-transfers.41851/
Someone points out the FreeBSD bug thread I've been trawling
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=187594
This is filed against 10.0, I don't know whether it would also be the same in 9.x branches, and what FreeNAS has done itself.
@jgreco even drops in to wonder if this is part of the infamous bug 1531, Performance Suckage
https://bugs.freenas.org/issues/1531
It shouldn't do that, obviously. The swapping isn't a great thing but it is fairly normal for some modest amount of swapout to occur over time. The ~4GB that unused bits of the FreeNAS middleware seems to like to occupy is the usual target. This is because there's a lot of stuff on a NAS that isn't used by your *particular* configuration.
Is there any chance that when it "crashes", it recovers over time? It's possible that you're running into some variation of the issues in bug 1531 relating to transaction group writes, which are supposed to be addressed by the new write throttle mechanism, but if you're maybe catching it before it is able to measure and adjust, it's very possible you could create a situation where the system might go catatonic for ... I'm just going to guess at 30-180 seconds. In such a case, what's actually happening is that one transaction group is being flushed to disk and another full transaction group has been created in the meantime. At that point, ZFS *must* pause, because it isn't committing to disk quickly enough.
I understand that Bug 1531 is actually because the write buffers get overloaded...
Anywho, I'll trawl through the FreeNAS bug tracker