[mythtv-users] sluggish system, potential HD failure, and how best to get back up and runnin

[Hika van den Hoven]

Hoi Simon,

Thursday, March 6, 2014, 12:06:35 PM, you wrote:

> Hika van den Hoven <hikavdh at gmail.com> wrote:

>> Note the difference between ramfs
>> and tmpfs. ramfs assigns space at need and tmpfs assigns an in kernel
>> predefined size. A size you can change with kernel options.

> As I read things, that's not correct.
> ramfs doesn't limit the size - so you can keep writing until memory
> is all used up and OOM killer will crash the system. tmpfs has a
> fixed upper size which you can set at mount time.
> I'm pretty certain that neither allocates the memory until it is
> actually used. I have a system (sort of semi-embedded and running
> from a CF card) where I've put several volatile filesystems on tmpfs
> - and until I realised the presence of the size option, I had the
> tmpfs volumes adding up to twice the available ram (and no swap on the system).

> https://wiki.debian.org/ramfs

> https://www.kernel.org/doc/Documentation/filesystems/tmpfs.txt
>> tmpfs puts everything into the kernel internal caches and grows and
>> shrinks to accommodate the files it contains ...

> http://www.thegeekstuff.com/2008/11/overview-of-ramfs-and-tmpfs-on-linux/

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I might have misinterpreted the preallocation part. But the default
size for tmpfs is quite small. I believe 8 Mb. If you set it higher
with ramdisk_size=xxx (in kb) it goes for all tmpfses.
If you use ramfs you have to be aware of its maximum size to prevent
swapping. Therefore I say only use it for /tmp and not for /var/tmp.

Tot mails,
  Hika                            mailto:hikavdh at gmail.com

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