Re: {SPAM?} Re: [SLUG] Booting from software RAID 1

From: Scotty Logan (scotty@scottylogan.com)
Date: Wed Jun 16 2004 - 15:10:39 EDT


On Jun 16, 2004, at 11:41 AM, Mario Lombardo wrote:
> Swap will span a number of disks--not just two. This adds performance
> and redundancy, but I've never tried to fail one of them to test it :(

Swap will span a number of disks, but it doesn't add redundancy, it
just adds more swap space (just like other Unices)

 From the swapon(2) man page on a RHEL3 system:
> Swap pages are allocated from areas in priority order, highest
> priority first. For areas with different priorities, a
> higher-priority area is exhausted before using a lower-priority
> area. If two or more areas have the same priority, and it is the
> highest priority available, pages are allocated on a round-robin basis
> between them.

So, the round robin allocation should increase performance if the
partitions are on separate disks (and separate controllers), but
there's no mirroring. If you loose one swap partition the system will
crash as soon as it attempts to bring back a page.

You have to mirror the swap partition(s) if you want a reliable system.
  How you do that depends on the OS, volume manager and hardware.

   Scotty

-- 
Never take life seriously - Nobody gets out alive anyway

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