zfs, raidz, spare and jbod

Claus Guttesen kometen at gmail.com
Wed Aug 6 09:54:30 UTC 2008

> I installed FreeBSD 7 a few days ago and upgraded to the latest stable
> release using GENERIC kernel. I also added these entries to
> /boot/loader.conf:
> vm.kmem_size="1536M"
> vm.kmem_size_max="1536M"
> vfs.zfs.prefetch_disable=1
> Initially prefetch was enabled and I would experience hangs but after
> disabling prefetch copying large amounts of data would go along
> without problems. To see if FreeBSD 8 (current) had better (copy)
> performance I upgraded to current as of yesterday. After upgrading and
> rebooting the server responded fine.
> The server is a supermicro with a quad-core harpertown e5405 with two
> internal sata-drives and 8 GB of ram. I installed an areca arc-1680
> sas-controller and configured it in jbod-mode. I attached an external
> sas-cabinet with 16 sas-disks at 1 TB (931 binary GB).

Replying to my own mail! :-) I believe I have found at least a
work-around to alleviate this issue. First of all I upgraded to zfs
ver. 11 by using Pawels patch. The upgrade itself does not solve any
issue. Then I upgraded the firmware as advised by Areca-support. The
firmware-upgrade has minor changes related to disk-temperature-reading
and will probably not change anything either.

I changed the configuration on each disk on the areca
arc-1680-controller to passthrough-mode and rebooted. After
re-creating the zpool I have not had any errors while copying 718 GB
of small files from my solaris-nfs-server. I'm performing a local copy
atm. and have 'zpool offline'd one disk and 'zpool replace'd with the

While the replace is in progress write-performance naturally takes a
hit but the resilver-progress is progressing steadily and will use
approx. 2 hours and 45 minutes in total to complete.


When lenity and cruelty play for a kingdom,
the gentlest gamester is the soonest winner.


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