Date: Wed, 15 Dec 1999 23:43:06 -0800 (PST) From: Matthew Dillon <dillon@apollo.backplane.com> To: Poul-Henning Kamp <phk@critter.freebsd.dk> Cc: Andrew Gallatin <gallatin@cs.duke.edu>, freebsd-current@FreeBSD.ORG Subject: Re: Serious server-side NFS problem Message-ID: <199912160743.XAA49890@apollo.backplane.com> References: <14376.945329041@critter.freebsd.dk>
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:> NFS uses the kernel 'boottime' structure to generate its version id.
:> Now normally you might believe that this structure, once set, will
:> never change. The authors of NFS certainly make that assumption!
:
:Is this another case of "lets assume the time of day is a random number" or
:is there any underlying assumption about time in this ?
:
:--
:Poul-Henning Kamp FreeBSD coreteam member
:phk@FreeBSD.ORG "Real hackers run -current on their laptop."
It basically needs to be a unique for each server reboot in order
to allow clients to resynchronize. The time has historically been
used for this purpose since NFS networks tend to require ntp
synchronization anyway. The time was used even before systems
had realtime clocks -- the kernel would load it's initial
time from the last access time stamp in the root filesystem (or
superblock, I forget which it was).
Under NFSv2 it wasn't as critical. Under NFSv3 the protocol will
break badly if the number stays the same across a reboot - there
would be a massive loss of data.
-Matt
Matthew Dillon
<dillon@backplane.com>
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