On Wed, 30 Jul 2008, Ross Smith wrote:
>
> I'm not saying that ZFS should be monitoring disks and drivers to
> ensure they are working, just that if ZFS attempts to write data and
> doesn't get the response it's expecting, an error should be logged
> against the device regardless of what the driver says. If ZFS is
A few things to consider:
* Maybe the device driver has not yet reported (or fails to report)
and error and just seems "slow".
* ZFS is at such a high level that in many cases it has no useful
knowledge of actual devices. For example, MPXIO (multipath) may be
layered on top, or maybe an ethernet network is involved.
If ZFS experiences a temporary problem with reaching a device, does
that mean the device has failed, or does it perhaps indicate that a
path is temporarily slow?
If one device is a local disk and the other device is accessed via
iSCSI and is located on the other end of the country, should ZFS
refuse to operate if the remote disk is slow or stops responding for
several minutes? This would be a typical situation when using
mirroring, and one mirror device is remote.
The parameters that a device driver for a local device uses to decide
if there is a fault will be (and should be) substantially different
than the parameters for a remote device. That is why most
responsibility is left to the device driver. ZFS will behave
according to how the device driver behaves.
Bob
======================================
Bob Friesenhahn
[EMAIL PROTECTED], http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer, http://www.GraphicsMagick.org/
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