SUMMARY: Big swap

From: Trubkina I. (asa@mmk.ru)
Date: Mon Oct 04 1999 - 23:44:24 CDT


QUESTION:

Can solaris 2.6 get raw swap partition greater then 2GB?
Manuals say that swap can use largefiles.
But after I add big swap partitioni(`swap -a /dev/dsk/c2t0d0s0`),
'swap -l' show raw swap part 2GB.
What can it be?

SUMMARY:

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From: "Marco Greene" <mgreene@sympatico.ca>

You can have more than 2 GB of swap space but at that point you need to
spread it accross different disks. Solaris 2.6 only recognized a maximum of
2GB swap partitions even if you have more.
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From: Casper Dik <casper@holland.sun.com>

It's largefile safe, i.e., it won't puke when confronted with a >2Gb file
but it will use at most 2Gb of a file.
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From: "Rothenanger, Juergen" <Juergen.Rothenanger@telekom.de>

I would say, 2.6 can only support 2 GB slices as swapfiles.
If you want more than 2 GB, use more swap partitions
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From: "Ian Durkacz" <I.Durkacz@sheffield.ac.uk>

Swap partitions greater than 2Gb were only introduced in Solaris 7
(as far as I know), and even there are only available if you use the
64-bit (and not the 32-bit) kernel.
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From: "Timothy Lindgren" <Timothy_Lindgren@enron.com>

Yes you can, but ONLY in 2 GB partitions, and you can't have 2 swap (physical
partitions, not logical) drives on the same device. That's called "stacking" --
and it's a bad bad thing. For best performance, your swap devices should be on
seperate controllers also... but that's not mandatory.
The amount of swap devices is limited only to the number of phyisical devices.
Such as 22 A5000 drives, each with 2 GB swap. Why anyone would do that is
beyond me, but i've seen some mighty large swap systems in my travels.
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From: Jason Marshall <jasonm@vsl.com>

You have to upgrade to Solaris 7 to get large swap partitions. However,
you can add a lot of 2 gig ones with the same effect.
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From: "Beck, Joe" <JBeck@dolsun.dol.state.nj.us>

to add to the issue of >2GB swap sizes on 2.6, be sure to test that your
system can still generate a core file.
I experienced problems with savecore earlier and was forced to decrease swap
to < 2GB
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From: "Otto, Doug" <otto@alldata.com>

You can set swap to larger than 2gb, but crashdumps will not work properly
unless each swap partition is 2.0gb or less. So you're better off using
multiple swap partitions if you require more than 2.0gb
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