On 03/04/12 20:03, David Dillow wrote:
> multipath implements path-checking on a *per-LUN* basis from user space.
> Today. No redesign needed. It already works on all SCSI transports.
>
> iSCSI has a protocol-defined mechanism to tell us when all LUNs on a
> given target are unavailable without waiting for the connection to be
> broken on a command timeout. I don't think FC has that, but it does have
> notification that a target is out of the fabric -- and all LUNs are
> unavailable. Both of these situations are communicated via an existing
> sysfs ABI, and the user space multipath code knows how to fail over and
> avoid checking those paths that are known to be bad.
>
> SRP does not have a protocol-defined way to check the link to the
> target. IB can tell us when a target leaves the fabric, like FC, but
> that's not what you're trying to implement -- you are attempting to fake
> the ping capability of iSCSI.

Let's focus on what we agree about. I'll repost the patch series but
without the last two patches (those that add dev_loss_tmo,
fast_io_fail_tmo, ping_interval, ping_timeout, failed_reconnects and
reconnect_tmo).

Bart.
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