On Mon, 2009-10-19 at 11:32 -0700, Joe Eykholt wrote:
>
> The FC-LS spec. says ELS timeouts should be 2 x R_A_TOV.
> The FC-GS spec. says CT timeouts should be 3 x R_A_TOV.
>
> We've been using E_D_TOV for both of those.
>
> Change for all ELS and CT requests except FLOGI, which we
> leave at 2 seconds (using E_D_TOV). One could argue that
> R_A_TOV is locally determined until after FLOGI succeeds.
>
> This does change FLOGI for vports which becomes FDISC.
> This does not change the REC/SRR timeout which is 2 seconds.
The FCP sec 11 suggests REC timeout at least >= E_D_TOV + 1 seconds and
default E_D_TOV as 2s, that means it should be least 3 second. The FCP
standard requires minimum value for REC_TOV and as far as I can tell
there is no restriction on larger REC_TOV value, that means we could
choose higher values also and I think we should since FCoE is mostly
used with 4G FC target ports and currently we allow upto 1024 commands
with each cmd could be up to 512KB and I've seen some config having low
IO throughout. So may be it should 20-30 seconds to avoid pre-mature REC
attempts.
I heard some HBA uses ULP_TOV (FC_SCSI_TM_TOV etc in libfc) as much as
60HZ, so perhaps that also need to be increased to avoid thrash due to
too early timeout and retry attempts.
What do you think ?
Vasu
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