9.0 crash, ssd or filesystem problem?

[Gary Aitken]

On 11/17/12 14:08, Warren Block wrote:
> On Sat, 17 Nov 2012, Gary Aitken wrote:
> 
>> On 11/16/12 21:38, Warren Block wrote:
>>> On Fri, 16 Nov 2012, Gary Aitken wrote:
>>>
>>>> On 11/16/12 12:10, Warren Block wrote:
>>>>
>>>>> Additional SSD suggestions: when creating partitions, leave out the swap
>>>>> partition.  If you have lots of memory, leave out the /tmp partition. Add
>>>>> that extra space to the /usr partition.
>>>>>
>>>>> Format the UFS filesystems with -Ut, for soft updates and TRIM support.
>>>>> (Make sure your SSD supports TRIM, almost all do.)  (I don't use soft
>>>>> updates journaling.)
>>>>>
>>>>> Use dd(1) to make a zero-filled file on /usr somewhere, say /usr/swap.
>>>>> Make it the size you want swap to be, and do not make it a sparse file.
>>>>> Tell the system to use the swapfile in /etc/rc.conf:
>>>>>
>>>>>    swapfile="/usr/swap"
>>>>>
>>>>> Use tmpfs for /tmp in /etc/fstab:
>>>>>
>>>>>    tmpfs        /tmp    tmpfs    rw,mode=01777    0    0
>>
>> When using the above in /etc/fstab to establish a tmp file,
>> how does the size of /tmp get established?
>> Is it limited only by the available swap,
>> or is it possible to put an upper bound on it that is smaller than swap?
> 
> It's free VM, which should be available RAM plus available swap.  Yes, you can easily limit the maximum size:
> 
>    tmpfs   /tmp   tmpfs   rw,mode=01777,size=1073741824   0   0
> 
> Untested, but I think that's correct.

Where is that documented?
I tried:
  man mount
  man fstab
    refers to "See the options flag (-o) in the mount(8) page and the 
               file system specific page, such as mount_nfs(8)..."
  man mount_tmpfs  (doesn't exist)
and don't see a "size" option anywhere.
oh... there it is
  man tmpfs

> There was a nice Sun white paper by Peter Snyder on tmpfs.  It's linked on the Wikipedia tmpfs page, but Oracle has broken the link.  Google has a rendered version of a PostScript copy (long URL):
> http://webcache.googleusercontent.com/search?q=cache:EXMeqvhFfrsJ:www.sun3arc.org/papers/OS/tmpfs_virtual_memory_filesystem.ps.gz+tmpfs+white+paper&cd=12&hl=en&ct=clnk&gl=us

Thanks.
Interesting, I would have thought swap space for something in a tmpfs was
not allocated until it needed to be swapped out.  As I read it, used tmpfs
space reserves space in swap.