[ale] who is eating my drive

[JD]

And I've used those "rules of thumb", until speaking with Sun SEs who
were pretty clear that for most users, anything beyond 2GB was a waste
of storage.  It's the same sort of reasoning why there's usually ZERO
reason to have a system core file larger than 2GB. All the interesting
things happen in the first 2GB.

The hostOS definitely has swap, it is just the VMs where I prevent swap
use.  Initially, I gave them all swap (didn't know any better), then saw
that it was never used - NEVER.  As memory requirements have grown, RAM
has been allocated to the VMs to stay ahead of the growth. I suppose if
usage spiked, there could be issues, but I've never seen that in 3 yrs.



On 05/31/2011 02:19 PM, Lightner, Jeff wrote:
> The old rule of thumb used to be two time RAM = swap.   For Linux I've
> seen it suggested 1 to 1.5 times is adequate but have run across many
> that don't bother at all.  As for me I always build swap because I
> believe it is better to have it and not need it than to need it and not
> have it.
> 
> I've never heard it suggested that virtual memory hurts performance.
> In fact it benefits it because you can preallocate more "memory" to
> processes than physically exists.   A lot of what is preallocated is
> never actually used.   
> 
> Remember "swap" is a historical name.   Back in the bad old days entire
> processes "swapped" out to disk to run there.   Now swap space is used
> for "paging" instead so it only pushes out old memory blocks to disk
> (and ideally never calls them back in).  The only time swap *seems* to
> "hurt" is when you're truly memory constrained and actually begin doing
> excessive page outs/pages ins.   In that case the issue isn't the swap
> but rather the lack of memory (or an excessive use of memory by runaway
> processes or the like).
> 
> 
> -----Original Message-----
> From: ale-bounces at ale.org [mailto:ale-bounces at ale.org] On Behalf Of JD
> Sent: Tuesday, May 31, 2011 2:05 PM
> To: Atlanta Linux Enthusiasts
> Subject: Re: [ale] who is eating my drive
> 
> Is having a swap device larger than 2GB useful for 99.98% of users?
> 
> Seems if you use that much virtual memory, performance would start to
> suffer.
> 
> For most of my VMs, I don't give **any** swap. I can ensure no over
> commitment happens.
> 
> 
> 
> 
> On 05/31/2011 01:28 PM, Narahari 'n' Savitha wrote:
>> Thanks for all your time.
>>
>> Here is the output of the fdisk -l command
>>
>> devusr at devusr-virtual-machine:~$ sudo fdisk -l /dev/sda
>>
>> Disk /dev/sda: 22.5 GB, 22548578304 bytes
>> 255 heads, 63 sectors/track, 2741 cylinders
>> Units = cylinders of 16065 * 512 = 8225280 bytes
>> Sector size (logical/physical): 512 bytes / 512 bytes
>> I/O size (minimum/optimal): 512 bytes / 512 bytes
>> Disk identifier: 0x00075d29
>>
>>    Device Boot      Start         End      Blocks   Id  System
>> /dev/sda1   *           1        1698    13630464   83  Linux
>> /dev/sda2            1698        2742     8386561    5  Extended
>> /dev/sda5            1698        2742     8386560   82  Linux swap /
> Solaris
>>
>>
>>
>> So what should I be looking here for ?
>>
>> -Narahari
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JD Pflugrath
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