zfs parition probing causing long delay at BTX loader

[Peter Maloney]

On 10/20/2011 07:23 PM, Steven Hartland wrote:
> Installing a new machine here which has 10+ disks
> we're seeing BTX loader take 50+ seconds to enumerate
> the disks.
I am running 8-STABLE. On my system with 22 disks, it took much longer
than a minute (maybe 5 minutes... not sure, but overall boot was about 7
minutes). While this time is passing, I can watch the leds on the disks
blink in order, many times in a loop.

My IO card is a LSI SATA/SAS 9211-8i 6Gb/s.

After I upgraded the firmware to version 11, it seems to take much less
time, but I didn't time it. And watching the LEDs last time I rebooted,
I don't notice them all blinking the same way. Instead, all were solid
for a second or two after the long wait, and then only the root disks.

So if you have the same card, I suggest you update the firmware. (I
updated for stability rather than boot speed, and it seemed stable until
it froze today, after 2 weeks)

> After doing some digging I found the following thread
> on the forums which hinted that r198420 maybe the
> cause.
> http://forums.freebsd.org/showthread.php?t=12705
>
> A quick change to zfs.c reverting the change to
> support 128 partitions back to 4 and BTX completes
> instantly like it used to.
>
> svn commit which introduced this delay is:-
> http://svnweb.freebsd.org/base?view=revision&revision=198420
>
> the specific file in that changeset:-
> http://svnweb.freebsd.org/base/head/sys/boot/zfs/zfs.c?r1=198420&r2=198419&pathrev=198420
>
>
> So the questions are:-
>
> 1. Can this be optimised so it doesn't have to test all
> of the possible 128 GPT partitions?
>
> 2. If a optimisation isn't possible or is too complex to
> achieve would it be better to have the partitions defined
> as an option which can be increased if needed as I suspect
> 99.99% if not 100% of users won't be making use of more
> than 4 partitions even with GPT, such as what the attached
> patch against 8.2-RELEASE achieves.
>
>    Regards
>    Steve
>
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Peter Maloney
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