Coredumps and swap - was part of Solaris Mem Consumption Post: 302223577

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Operating Systems Solaris Coredumps and swap - was part of Solaris Mem Consumption Post 302223577 by Neo on Saturday 9th of August 2008 02:43:10 PM

08-09-2008

Administrator

Quote:

Originally Posted by reborg

There is a lot of infomation in this thread which is not valid. Almost everything Incredible has stated in this thread is incorrect in terms both of system configurations and reasons for choosing swap size.

A few points worth note.

You don't need to allocate any swap space to deal with savecores, and have not since Sorlais 8.
Solaris will never go into a panic-reboot cycle as a result of not having savecore space. It will simply not save a core dump if it has no space.
Twice memory as swap is no longer a good choice unless you really can't afford to upgrade.
If you have a lot of pagout you do not have enough memory, it's as simple as that.
You do not need minimum 16GB swap for 64 or 128GB of memory, but you may need to have more swap if you have applications using ISM (Intimate shared memory) or DISM (Dynamic Intimate Shared Memory) such as Sybase or Oracle databases.
There is no reason to treat an M-Series differently from any other Solaris box.

In summary you can get by to some extent if you don't have enough memory by adding swap, but it will hurt performance. Ideally you should have enough memory to run all your applications in memory, and the general rule of thumb nowadays is about 30% of memory for swap but there are more detailed reccomendations in the Solaris documentation.

Jim Laurent at Sun wrote a blog on this topic about a year ago, which you could look up.

EDIT: Found the blog:Solaris FAQ: Myths and facts about Solaris swap space : Jim Laurent's Weblog

Excellent followup reborg. Thanks for taking the time to set the record straight.

Neo

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LEARN ABOUT HPUX

remote_nfs_swap

remote_nfs_swap(5)						File Formats Manual						remote_nfs_swap(5)

NAME

       remote_nfs_swap - enable swapping across NFS

VALUES

   Default
   Allowed values
DESCRIPTION

       This  tunable  controls adding a NFS filesystem for use as swap.  If is set to only local filesystems and devices can be used for swap.	If
       it is set to both local and networked file systems can be used for swap.

       Historically, this tunable was used in NFS clusters that are no longer supported, but this capability has not yet been removed.

   Who Is Expected to Change This Tunable?
       Anyone.

   Restrictions on Changing
       Changes to this tunable take effect on the next boot.

   When Should the Tunable Be Turned On?
       Almost never.  As previously mentioned, this tunable was designed for systems which are not in use  today.   Only  systems  with  extremely
       robust NFS capabilities should even consider using NFS for swap.

   What Are the Side Effects of Turning the Tunable On?
       If  the	value  is  set to and a NFS partition is added as swap, then some kernel memory will be set aside for NFS transactions to the swap
       file system.  The kernel will then use the NFS swap partition just the same as a local file system.  If the NFS capabilities of the  system
       are  not  robust,  this	could lead to extremely long swap times (both swap in and swap out), and possibly a loss of memory because all the
       reserved memory and more could be used by NFS (just when memory pressure is high) causing the need for swap.

   When Should the Tunable Be Turned Off?
       Unless you are positive that the NFS system can handle the load of being used as swap, and does not have a local file system or disk  drive
       to spare, this tunable should be set to

   What Are the Side Effects of Turning the Tunable Off?
       Any  previously	defined  NFS  swap  filesystems will no longer be allowed.  Kernel memory will not be reserved for NFS transactions due to
       swap.

   What Other Tunables Should Be Changed at the Same Time?
       None.

WARNINGS

       All HP-UX kernel tunable parameters are release specific.  This parameter may be removed or have its meaning changed in future releases	of
       HP-UX.

       Installation  of  optional  kernel  software, from HP or other vendors, may cause changes to tunable parameter values.  After installation,
       some tunable parameters may no longer be at the default or recommended values.  For information about the effects of installation  on  tun-
       able  values,  consult  the documentation for the kernel software being installed.  For information about optional kernel software that was
       factory installed on your system, see at

AUTHOR

       was developed by HP.

							     Tunable Kernel Parameters						remote_nfs_swap(5)

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