Swap/dump size limit per disk

[Stefano_1]

Can anyone please let me know which is the swap/dump limit for a single disk, under HP-UX 11 64 bit?
thanks for your help...

[harry d brown jr]

I'm not aware of any limit, but the number one rule, if you require large amounts of swap, is not to put all of your swap on one disk. 1.5 to 2 times memory is usually more than adequate.

live free or die
harry

[Santosh Nair_1]

I don't believe there is a limit on the size of swap on a given disk. There is however, a limit on the size of swap on the system as defined by maxswapchunks. This kernel parameter defines the maximum number of swapchunks, where swapchunks are defined as 2k blocks that the system can have.

-Santosh

[Alan Riggs]

I believe that dump volumes are still restricted to the first 2GB of a physical disk (though I have not checked this for 11i).

Swap volumes need only to contiguous, to the bst of my knowledge. There is no restriction on the size of swap areas except for primary swap+dump, which is still restricted by the 2 GB limit.

[Stefano_1]

The rule is true also for the swap/dump space or only for the swap space?
I have a server with 8GB of memory and 2 18GB disks and 4 4GB disks.
Any suggestions?

[Stefano_1]

Alan, where I can find the information relative this limit?

[harry d brown jr]

Well you probably don't need more than 12gb's of swap/dump. Are these disks part of VG00?

[Stefano_1]

Harry,I can decide wich volume group to utilize

[harry d brown jr]

Then put 4gb on each 18gb drive, and put 2gb on two 4gb drives. That way you spread out the I/O.

Santosh recommended looking at maxswapchunks, do you know the value of this?

live free or die
harry

[Roger Baptiste]

>

With 8Gb memory -> swap can be anywhere from 8gb to 16gb, depending on the applications running on the box. 16gb would be a overkill. I would settle for 8gb and then boost it to 12Gb, if necessary. You can spread this as 2Gb swap volumes on the disks. Two 2Gb on the root disk and the remaining on the 4 gb disks.
The maximum swap which you can have on the system is limited by the max sizes of two kernel parameters maxswapchunks and swapchunk

Regarding dump, here is a good document on how to configure dump size:
http://us-support.external.hp.com/cki/bin/doc.pl/sid=d1f47bae1d0d4dad58/screen=ckiDisplayDocument?docId=200000054664128 (docid: KBRC00006362)

or the online doc s at: http://docs.hp.com/hpux/onlinedocs/os/syscrash.html


HTH
raj

[Stefano_1]

yes Hanry...
thanks.
Do you know where I can find the information relative to the limit for the primary swap/dump space?

[harry d brown jr]

Santosh explains it here:

http://forums.itrc.hp.com/cm/QuestionAnswer/1,11866,0x5ad9cf38d6bdd5118ff10090279cd0f9,00.html

live free or die
harry

[James R. Ferguson · Accepted solution]

Hi Stefano:

Like Alan, I recalled some documented limitations. From Knowledge Base document #A4824565 for 10.20 [ BUT READ ON }:

/begin_quote/

The /stand and dumps file systems are restricted to either 2GB or 4GB, depending on version of iodc firmware on the boot interface PCA...Some new hardware interfaces may support up to 8TBs...There are no restrictions on the maximum size of primary swap with respect to the HP-UX operating system.

Hardware interface limitations will determine the size limit of any disk file system or partition on a given disk. That is, the SCSI
controller that controls the disk will impose a limit; depending on the controller, the limit is either the first 2GB or 4GB of the disk.

/end_quote/

Clearly that settles the issue of primary swap size at least. I would think that 'lvlnboot -d' would "complain" appropriately. Perhaps this helps.

Regards!

...JRF...

[Alan Riggs]

Like James supplied, the limitation was never on primary (or other) swap but on the dump device. If primary swap is also functioning as your dump device (a standard configuration, though I prefer to segregate dump where possible) it applies to that primary swap volume. I did not remember that some iodc allowed 4GB or greater.

As to "what would I do", it really depends upon the amount of running process space that I think I will need. If it is more than 14GB, then I would allocate additional device swap as necessary. Otherwise, I would allocate 4 2GB swap areas (on separate disks) and activate psuedo-swap in the kernel.

[Frank Slootweg]

Concerning the 2GB or 4GB size limitation *per* *dump* (not swap) device:

As James quoted, that is a hardware/firmware (IODC, I/O Dependent Code) issue, not a software issue (at least not primarily) i.e. it depends on the particular hardware/system/model.

As to where it (i.e. the general issue) is documented: In the (only) manual page which is related to dump devices, the lvlnboot(1M) manual page.