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Old 10-28-2008, 06:47 AM
Christopher Chan
 
Default Apparently no swap configured

Ian Masters wrote:
> Christopher Chan wrote:
>> Well...it won't do that...but it should raise a flag on no swap being
>> configured after you were done partitioning and assigning/setting
>> filesystems.
>
> As far as I can remember there was no such 'flag'. That's precisely the
> kind of thing that would have made me jittery at the install stage.
>

Was it Centos 5 that you installed? IIRC, the Centos/RHEL 4 installer
would have asked you about the lack of swap assigned. I have only done
one Centos 5 installation and I did not miss telling it to use the swap
lv as swap so I cannot say whether the Centos 5 installer will do that.
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Old 10-28-2008, 06:53 AM
Ian Masters
 
Default Apparently no swap configured

Christopher Chan wrote:
> Was it Centos 5 that you installed? IIRC, the Centos/RHEL 4 installer
> would have asked you about the lack of swap assigned. I have only done
> one Centos 5 installation and I did not miss telling it to use the swap
> lv as swap so I cannot say whether the Centos 5 installer will do that.

It was CentOS 5.2.

To me it seems slightly unlikely that functionality in v4 would be
missing in v5. Having said that, it was my first CentOS install, and
first experience of using LVM.

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Old 10-28-2008, 09:23 AM
"William L. Maltby"
 
Default Apparently no swap configured

On Tue, 2008-10-28 at 00:21 -0700, John R Pierce wrote:
> Ian Masters wrote:
> > which show your swap partition, whereas on my problem system, 'swapon
> > -s' produces no output at all.
> >
>
> ok, that confirms your supposition, you have no swap configured.

All this raised a question in my mind. What's the value of have a swap
managed by LVM? ISTM that: 1) swap is usually configured to be the
maximum needed (depending on system usage and who you're talking to, 1,
2 times real memory usually), 2) additional overhead with no gain (I
know several claim little to no overhead but background tells me there
is always *some* even if small), 3) if you *do* increase this LV size to
increase swap size, another mkswap is needed to "map" the new space, 4)
more swap can be added by defining more LVs for swap, a partition
dedicated to swap or a swap file with a file system and then mkswap and
activating it.

I always just define a partition for that, flag it as swap in the
partitioning process and go with that set up. I can envision the
convenience of being able to temporarily disable swap, slapping a file
system on it and addressing some need. Or even destroying the LV and
freeing the PV for other use. But that sounds sort of far-fetched.

My *guess* is that the OP failed to mark a partition type of 82 for swap
during install and thus ended up with this odd configuration. It's only
a guess though.

Wouldn't it be better to vgremove/pvremove that thing and flag it as
type 82, mkswap, etc.?

> <snip sig stuff>

--
Bill

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Old 10-28-2008, 09:25 AM
"William L. Maltby"
 
Default Apparently no swap configured

On Tue, 2008-10-28 at 00:21 -0700, John R Pierce wrote:
> Ian Masters wrote:
> > which show your swap partition, whereas on my problem system, 'swapon
> > -s' produces no output at all.
> >
>
> ok, that confirms your supposition, you have no swap configured.

Although I disagree, some on this list have proclaimed that a "properly
configured" (for the intended use I guess) system needs no swap.

> <snip>

--
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Old 10-28-2008, 02:29 PM
Scott Silva
 
Default Apparently no swap configured

on 10-28-2008 3:25 AM William L. Maltby spake the following:
> On Tue, 2008-10-28 at 00:21 -0700, John R Pierce wrote:
>> Ian Masters wrote:
>>> which show your swap partition, whereas on my problem system, 'swapon
>>> -s' produces no output at all.
>>>
>> ok, that confirms your supposition, you have no swap configured.
>
> Although I disagree, some on this list have proclaimed that a "properly
> configured" (for the intended use I guess) system needs no swap.
>
>> <snip>
>
A properly configured system "can" need no swap for day to day operations, but
you only need *one* runaway process to max out the memory and bring the system
to a crashing halt. A little swap is just like a cheap insurance policy. You
hope you don't need it, but if you do, you are glad it was there.

Even though the recommended swap is 2 times system memory, I have never made a
swap partition over 2 GB. Maybe I am also flirting with disaster, but haven't
been bit yet in years. Usually a run away process that hits into swap gives
enough time for the kernel to kill it off before the whole system dumps.


--
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You hope everybody uses it, and
you notice quickly if they don't!!!!

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Old 10-28-2008, 03:24 PM
"nate"
 
Default Apparently no swap configured

William L. Maltby wrote:

> All this raised a question in my mind. What's the value of have a swap
> managed by LVM? ISTM that: 1) swap is usually configured to be the

I think the main reason would be simplicity, assuming you have
other volumes created and not just a single VG with a single
LV in it for swap.

Though I don't use LVM on the internal disks of my systems, have
had too many headaches over the years with anaconda puking during
installation with kickstart when using LVM. I only use LVM on
SAN volumes.

nate

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Old 10-28-2008, 11:33 PM
Christopher Chan
 
Default Apparently no swap configured

nate wrote:

William L. Maltby wrote:


All this raised a question in my mind. What's the value of have a swap
managed by LVM? ISTM that: 1) swap is usually configured to be the


I think the main reason would be simplicity, assuming you have
other volumes created and not just a single VG with a single
LV in it for swap.

Though I don't use LVM on the internal disks of my systems, have
had too many headaches over the years with anaconda puking during
installation with kickstart when using LVM. I only use LVM on
SAN volumes.


Centos/RHEL 5's anaconda has that licked. Feel free to do it with
kickstart again. I have eight new boxes setup with kickstart doing lvm
on mirrored partitions. /boot on its own mirrored partition.

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Old 10-28-2008, 11:38 PM
Christopher Chan
 
Default Apparently no swap configured

Even though the recommended swap is 2 times system memory, I have never made a
swap partition over 2 GB. Maybe I am also flirting with disaster, but haven't
been bit yet in years. Usually a run away process that hits into swap gives
enough time for the kernel to kill it off before the whole system dumps.



I am sorry but that 'recommended' swap should be twice the of RAM
installed is complete nonsense and I treat the LPI certificate as
rubbish precisely because they subscribe to that nonsense. The roots of
swap = 2xRAM comes from an old release of Solaris which REQUIRED swap be
2xRAM. In today's environment, there is no standard rule for how much
swap to configure. If there is one, it is simply 'configure as much as
you need and want.'

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Old 10-29-2008, 04:23 AM
Ian Masters
 
Default Apparently no swap configured

Nate

> If that volume is not in use by anything else you should
> be perfectly able to do:
>
> mkswap /dev/VolGroup00/swap
> swapon /dev/VolGroup00/swap
>
> then add something like this to fstab:
> /dev/VolGroup00 swap swap defaults
0 0

Shouldn't the fstab entry be:

/dev/VolGroup00/swap swap swap defaults
0 0

Just want to double-check before I dive in.

Thanks

Ian Masters

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Old 10-29-2008, 06:06 AM
"nate"
 
Default Apparently no swap configured

Ian Masters wrote:

> Just want to double-check before I dive in.
>

yep your right..


nate

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