First off: SAP has a long history of "recommending" certain amounts of swap. You can safely ignore these recommendations as they are complete nonsense.
If your system has some memory shortage it will start swapping. Once it does so you need the swap space and once this swap space it exhausted (or nearly exhausted) your system will start killing processes - so far, so common. But long before your swap space is exhausted you will have a severe performance degradation and you customers will be all over you to get the system back to speed - so far, so common either.
But as long as your system doesn't have a memory shortage you don't need swap space - *any* swap space! This means, while it is a god idea to have some swap space as a contingency you don't *need* it (under "normal" circumstances, which means there is indeed enough memory) at all.
SAP now recommends to configure swap space based on a simple formula: your current amount of memory times some factor (if i remember correctly it was 2). Would you increase your memory, which would make swapping even less probable their recommended amount would even increase, while there is a simple way to meet their requirements: reduce the memory of the system, which will make swapping occur more often, but SAP will recommend a smaller swap space for this (in fact now ill-tuned) system!
You see, their recommendation is simply bovine manure.
Historically the AIX kernel used an "early swap allocation" and allocated swap space for every started program, so the recommendation of SAP made - least some - sense back then. Since the days of AIX 5 (or was it with 5.1? A lot of years back for sure!) IBM changed that and now AIX uses late swap allocation. Since this change the recommendation makes no sense at all.
Regarding your error message: There is a parameter for each LV, which shows the maximum numbers of LPs that can be assigned to it. The command xoops told you will increase this maximum for the LV which holds your swap space. You can also do it using SMIT by issuing
Code:
smitty chlv
and follow the menus on screen.
I hope this helps.
bakunin
Moderator's Comments:
BTW.: i have changed the threads title to "recommended".
Hy all,
i've a little problem with the size of the swap. I've an old solaris machine, with 4Go, and swap is taking 500Mo for only 1% used at any time.
So : how can i change this size without problems ?????
(ok it may be a stupid question, but it's a real problem when you lose about 1 or 2... (3 Replies)
Hello all,
I just got a laptop with redhat linux 7.2 installed, but during the installation the installer only put 1gig of sawp space( this laptop has 1gig of RAM). To my understanding when creating swap space, the size is determine by double the RAM. Therefore my question is that how do I... (2 Replies)
I have a machine: SunOS <server> 5.9 Generic_117171-15 sun4u sparc SUNW,Sun-Fire-480R
It has these filesystems:
Filesystem size used avail capacity Mounted on
/dev/md/dsk/d0 19G 15G 3.9G 80% /
/proc 0K 0K 0K 0% /proc... (6 Replies)
few questions
a. where can I find the RAM of a server? im about to install redhat on a server (reformat). need to know because it will be my basis for swap size. i saw something line 3048MB detected upon boot. is this the memory?
b. what is the command in lunux to check the original size of... (2 Replies)
Dear All,
How to increase the swap size when physicall memory reaches 60 %. OR it can be only done after the physicall memory is full.
Rgds
Rj (8 Replies)
Hi All,
I want to know how to understand the actual swap size.
My o/p shows as below
root@ecovs1a # swap -s
total: 4546056k bytes allocated + 358856k reserved = 4904912k used, 5046688k available
root@ecovs1a # swap -l
swapfile dev swaplo blocks free
/dev/md/dsk/d31 ... (9 Replies)
Hi Experts,
Need your advise in determining the size of swap space in of the new HP-Ux server.
Server is having 32G of physical memory.
Ideally what amout of physical memory should be allocated as a swap space?
Following document from HP suggests to have minimum swap space... (2 Replies)
Hi,
the /tmp size is less whereas the size allocated to swap is quite big. how to increase the size of /tmp -
#: swap -l
swapfile dev swaplo blocks free
/dev/md/dsk/d20 85,20 8 273096 273096
#: swap -s
total: 46875128k bytes allocated + 2347188k reserved =... (2 Replies)
Discussion started by: psb74
2 Replies
LEARN ABOUT DEBIAN
bup-margin
bup-margin(1) General Commands Manual bup-margin(1)NAME
bup-margin - figure out your deduplication safety margin
SYNOPSIS
bup margin [options...]
DESCRIPTION
bup margin iterates through all objects in your bup repository, calculating the largest number of prefix bits shared between any two
entries. This number, n, identifies the longest subset of SHA-1 you could use and still encounter a collision between your object ids.
For example, one system that was tested had a collection of 11 million objects (70 GB), and bup margin returned 45. That means a 46-bit
hash would be sufficient to avoid all collisions among that set of objects; each object in that repository could be uniquely identified by
its first 46 bits.
The number of bits needed seems to increase by about 1 or 2 for every doubling of the number of objects. Since SHA-1 hashes have 160 bits,
that leaves 115 bits of margin. Of course, because SHA-1 hashes are essentially random, it's theoretically possible to use many more bits
with far fewer objects.
If you're paranoid about the possibility of SHA-1 collisions, you can monitor your repository by running bup margin occasionally to see if
you're getting dangerously close to 160 bits.
OPTIONS --predict
Guess the offset into each index file where a particular object will appear, and report the maximum deviation of the correct answer
from the guess. This is potentially useful for tuning an interpolation search algorithm.
--ignore-midx
don't use .midx files, use only .idx files. This is only really useful when used with --predict.
EXAMPLE
$ bup margin
Reading indexes: 100.00% (1612581/1612581), done.
40
40 matching prefix bits
1.94 bits per doubling
120 bits (61.86 doublings) remaining
4.19338e+18 times larger is possible
Everyone on earth could have 625878182 data sets
like yours, all in one repository, and we would
expect 1 object collision.
$ bup margin --predict
PackIdxList: using 1 index.
Reading indexes: 100.00% (1612581/1612581), done.
915 of 1612581 (0.057%)
SEE ALSO bup-midx(1), bup-save(1)BUP
Part of the bup(1) suite.
AUTHORS
Avery Pennarun <apenwarr@gmail.com>.
Bup unknown-bup-margin(1)
10-13-2011
