getting to 4K disk blocks in ZFS

[Steven Hartland]

----- Original Message ----- 
From: "Matthew D. Fuller" <fullermd at over-yonder.net>


> On Mon, Oct 13, 2014 at 11:48:27AM -0700 I heard the voice of
> Darren Pilgrim, and lo! it spake thus:
>> 
>> If the default is 4k and (for the limited time they're still common)
>> you use true 512b disks, you can waste space.  Sure, but how much
>> space?
> 
> The median file in /usr/ports is 408 bytes.  Over 90% of the files are
> under 2k, which means the wastage for them is over 100% (before
> counting what gain compression might get).  A little offhand mathery
> says it's about 78% extra overhead on the whole.
> 
> And that includes the almost hundred megs (over 22% of the total size
> of the FS) for the INDEX.db, plus the ~90 megs of the flat INDEX files
> (another 20%).  If you pull those out, the overhead is 130%.
> 
> 
> (To be sure, relatively few people have ports trees eating most of
> their space, but still; it's pretty pathological.  I for one did
> decide some years back to always force 4k on any new FSen to make
> future life simpler, accepting the bloat, but it's there.)

And thats before you add the overhead if your running RAIDZ...

A good read on this is
http://blog.delphix.com/matt/2014/06/06/zfs-stripe-width/

    Regards
    Steve