ZFS tuning [was: hardware for home use large storage]

[Peter Jeremy]

On 2010-Feb-16 09:59:46 -0800, Jeremy Chadwick <freebsd at jdc.parodius.com> wrote:
>On Tue, Feb 16, 2010 at 11:06:43AM -0600, Barry Pederson wrote:
>> maybe something like this tacked on the end of the script (excuse my
>> Perl, I'm a Python guy).
>> 
>> ----
>> #### Loader Settings #############
>> open(LOADER, '/boot/loader.conf');
>> print "\n/boot/loader.conf settings:\n";
>> while (<LOADER>){
>>     chomp;
>>     if (/^\s*(zfs|vfs\.zfs|vm\.kmem)/){
>>         print "\t$_\n";
>>     }
>> }
>> ----
>
>Major problems with the above code:
>
>1) Opens /boot/loader.conf for rw access; should be read-only
Wrong.  It opens /boot/loader.conf read-only, as it should.

>2) Makes the assumption /boot/loader.conf exists
Accepted but it was offered as a proof-of-concept.

>3) Does not close the fd
This is hardly a "major problem" in a short once-through script.

>4) Excessively quotes variables for no justified reason
If you mean including the $_ inside "", this is a standard perl idiom.

>5) Makes some bad assumptions about the contents of the file (ex.
>   comments with the word "zfs" in them would match)
Wrong.  It only matches "zfs" as the first non-blank text on
a line - which means it can't be a comment.

So that's one real deficiency in a proof-of-concept script written by
someone who does not claim to be comfortable with perl.

>The code should really be something like what's below.  This should
>be much more manageable as well (@tunables that is), although I always
>worry when using grep()...

Whilst we are picking nits, your script has the following issues:
- unnecessary trailing wildcard matches in the regexps
- "grep" misused as "map"
- "die" is probably not appropriate for embedding into another script
- No useful error message if /boot/loader.conf can't be opened.
- Doesn't correctly handle optional whitespace around "="
- No heading to explain what is being reported.
- Doesn't allow for "zfs" as a top-level identifier

Overall, Barry's script makes an excellent proof-of-concept - which is
what he was offering.

-- 
Peter Jeremy
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