More than 32 CPUs under 8.4-P

Paul Kraus paul at
Sun May 19 20:28:16 UTC 2013

On May 19, 2013, at 11:51 AM, Dennis Glatting <freebsd at> wrote:

> ZFS hangs on multi-socket systems (Tyan, Supermicro) under 9.1. ZFS does
> not hang under 8.4. This (and one other 4 socket) is a production
> system.

	Can you be more specific, I have been running 9.0 and 9.1 systems with multi-CPU and all ZFS with no (CPU related*) issues.

* I say no CPU related issues because I have run into SATA timeout issues with an external SATA enclosure with 4 drives (I know, SATA port expanders are evil, but it is my best option here). Sometimes the zpool hangs hard, sometimes just becomes unresponsive for a while. My "fix", such as it is, is to tune the zfs per vdev queue depth as follows:


The defaults are 5 and 10 respectively, and when I run with those I have the timeout issues, but only under very heavy I/O load. I only generate such load when migrating large amounts of data, which thankfully does not happen all that often.

Paul Kraus
Deputy Technical Director, LoneStarCon 3
Sound Coordinator, Schenectady Light Opera Company

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