Re: tuning a VERY heavily (30.0) loaded s cerver

[Matt Dillon]

:Hey, talking about large amounts of swap, did you know that:
:  4.2-STABLE FreeBSD 4.2-STABLE #1: Sat Feb 10 01:26:41 PST 2001
:has a max swap limit that's possibly 'low':
:
:  b: 15912412        0      swap                        # (Cyl.    0 - 990*)
:  c: 17912412        0    unused        0     0         # (Cyl.    0 - 1114*)
:
:If I made b == c, then i couldn't swapon it.
:
:Don't ask why I have that much swap, I just needed a bunch on a dedicated
:disk. :)
:
:-- 
:-Alfred Perlstein - [[EMAIL PROTECTED]|[EMAIL PROTECTED]]

    You would have to reconfigure your kernel to reduce NSWAP from 4 to
    either 2 or 1.

    Bitmap overhead for swap is 2 bits per page (4K) of swap.

    There is a maximum of 2G / 16 / NSWAPDEV blocks (512 byte chunks) of swap.
    If NSWAPDEV is 4, this comes to:

        2G/16/4x512 = 17GB.

    So you would be able to create approximately four 17GB swap partitions.
    If you reduce NSWAP to 2 you would be able to create approximately
    two 34GB swap partitions.  If you reduce NSWAP to 1 you would be able
    to create approximately one 68GB swap partition.

                                                    -Matt


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