DragonFly users List (threaded) for 2009-02
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DragonFly users List (threaded) for 2009-02
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Re: Hammer FS: imposing a size limit on PFS?

From: Bill Hacker <wbh@xxxxxxxxxxxxx>
Date: Thu, 26 Feb 2009 11:02:10 +0800

Matthew Dillon wrote:
    Our installer support for HAMMER isn't advanced enough yet.  What we
    really want is a UFS /boot, swap, and then a HAMMER root that covers
    everything else.

I would (and have) taken that a step farther.

'once upon a time'

'/usr' was not part of the core essential. It really was 'userland'

Long since, far too many of the *system's* 'needful things' in the way of binary and libs migrated there. Recall my push to get a decent static-compiled editor into the root partition so we could at least edit a FUBAR'ed /etc/rc.conf w/o having to manually mount a (potentially damaged) /usr.

'These days' one gains a bit of respect for NetBSD / OpenBSD plutting things into /usr/pkg rather than /usr/local, if only to keep them out of the way of 'real userland' - and even looks yearningly at Linux use of '/opt'

Reality is that a 'healthy' system needs '/usr' (libs and binaries) and '/var' (pidfiles, logs, and spools) to be mounted more or less 'at all costs'.

Ergo, one wants to push anything that really IS userland and user-app, or 'production use' specific out into bespoke mounts.

True whether the box is to be used for familiarization, learning, experimenting, OR 'production'.

And regardless of fs chosen....

The idea with HAMMER is you just create one big filesystem and use the PFS functionality to break it up into separate management domains. Currently a size limit may not be placed on a PFS.


I want my 'core' to be as damage-resistant as can be. So long as it IS such, and can boot and mount rapidly and respond to console - better yet ssh from afar - I have the wherewithal to manage, repair, or even nuke and reinstall - all the rest.

Ergo, absent a 'netboot' or flash/USB boot - I submit:

'Best Current Practice';

Minimum with one device:

- A modest 'slice' for the OS install, partioned and UFS, OR 'shared' with hammer.

- One or more SEPARATE partons if not SLICES for hammer-as-bulk storage, application support, etc.

IOW - not entangled in any way with '/usr', '/var'. You can wipe it and start over over-the-wire, as the 'core' is isolated.

Better yet - multiple devices, where second and subsequent devices where hammer owns the entire device.

If we cannot isolate and protect the 'core' within a hammer PFS, then we should not put it into the same PFS 'family' and open it to overflow or damage.

JM-scar-tissue's-2CW - but we have found this 'safe' from CP/M 1.X onward.

Logs and spool aside, 'core' has slow or no rate of change.


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