Swap Dump Areas

[Imraan Abdul]

Hi .....
Could someone please help ???
I have read on past forums that the swap/dump area on a System should be at least twice the size of your memory allocation.
I have increased my Swap areas on 2 Servers - What priorities should I allocate ????
The existing swap logical volume - /dev/vg000/lvol2,was configred on "pri 1".When I added the 2nd i configured it aslo on "pri 1" - Is this okay or do i need to change the priorities.
My current memory on both server's is 256MB - I have made the Swap 768MB - Could somone please advise me ???

[Eugen Cocalea]

Hi,

It's ok to have two swap partitions with the same priority.

Read the manpage of 'swapinfo' the section 'Paging Allocation' for further info.

E.

[Ravi_8]

Hi,
512(265x2) MB swap would have been sufficient.what you have allocated now (768MB) is also ok. and keep the priority 1 as it is.

[James R. Ferguson]

Hi:

Requirements for swap space vary depending on the environment, and there are few hard, fast rules.

Check your swap utilization with:

# swapinfo -tam

When you are setting up device swap, you will optimize its performance if you make your second (and third) swap the *same* priority as the primary swap, and the *same* size, but, make sure that you do *not* place the secondary swap space on the same disk as the primary. In this way you will interleave swap I/O, oscillating it between the two devices on the separate disk.

Regards!

...JRF...

[A. Clay Stephenson]

Hi:

The old 'rule of thumb' of sizing swap at 2-3 x memory seldom apply anymore; however, in your case with only 256MB of memory that is probably not a bad idea. On machines with large amounts of RAM (4GB & up or so) then it is very common to only have 256-512MB of swap because the machines never swap. When you set swap priorities, if the swap is on different physical devices then the swap priorities should be set to the same value so that thew swap will be interleaved among them. However, if the swap devices are located on the same physical device, then the swap priorities should NOT be set the same. The head positioning mechanism will be moving between the two areas on the same disk like a madman.

Regards, Clay

[Roger Baptiste]

Hi,

I have read on past forums that the swap/dump area on a System should be at least twice the size of your memory allocation.
>>> That's a rough guideline, but the
>> size of swap depends on the system
>> and memory size and the usage

I have increased my Swap areas on 2 Servers - What priorities should I allocate ????

>> If they are are different disks(VGs),
>> their priority should be the same and
>> their size should be the same.
>> this will spread the swap load on
>> different disks bringing better
>> performance.

The existing swap logical volume - /dev/vg000/lvol2,was configred on "pri 1".When I added the 2nd i configured it aslo on "pri 1" - Is this okay or do i need to change the priorities.

>> It is fine, as long as the the second
>> swap is sitting on a different disk of
>> VG00 or is on a different VG altogether.
>> To find this: do a pvdisplay on the
>> second swap. it will list the disks used
>> by the swap.

My current memory on both server's is 256MB - I have made the Swap 768MB - Could somone
>> That is fine. With a small memory
>> like 256 Mb, having the swap more than
>> two times makes sense.
>> BTW, swap and dump can be shared as is
>> in your configuration. Also, to make
>> sure the system will dump , check the
>> /etc/rc.config.d/savecore configuration
>> and ensure the /var/adm/crash filesystem
>> is setup and has 512 MB space.

-R

[Sanjay_6]

Hi Imraan,

Take a look at the threads below for more info.

http://us-support2.external.hp.com/cki/bin/doc.pl/sid=e44af48a0d4725de60/screen=ckiDisplayDocument?docId=200000048595137

http://us-support2.external.hp.com/cki/bin/doc.pl/sid=e44af48a0d4725de60/screen=ckiDisplayDocument?docId=200000024602557

http://us-support2.external.hp.com/cki/bin/doc.pl/sid=e44af48a0d4725de60/screen=ckiDisplayDocument?docId=200000024631931

http://us-support2.external.hp.com/cki/bin/doc.pl/sid=e44af48a0d4725de60/screen=ckiDisplayDocument?docId=200000024603386

Hope this helps.

thanks