ZFS obn FreeBSD hardware model for 48 or 96 sata3 paths...

Joshua Boyd boydjd at jbip.net
Sat Sep 17 04:13:42 UTC 2011


On Fri, Sep 16, 2011 at 9:22 PM, Jason Usher <jusher71 at yahoo.com> wrote:

>
> So I will boot of a pair of mirrored SSDs formatted UFS2 - easy.  But I
> would also like to spec and use a ZIL+L2ARC and am not sure where to go ...
> the system will be VERY write-biased and use a LOT of inodes - so lots of
> scanning of large dirs with lots of inodes and writing data.  Something like
> 400 million inodes on a filesystem with an average file size of 150 KB.
>

400 million inodes on a single file system is not going to work out well. It
doesn't matter /what/ file system you use, it will end up barfing. I'd
recommend creating lots of zfs filesystems on your zpools. With 400 million
inodes, I'm HOPING that they're atleast divided into subdirectories, create
a zfs for each subdirectory. That'll help a lot.


>
> - can I just skip the l2arc and just add more RAM ?  Wouldn't the RAM
> always be faster/better ?  Or do folks build such large L2arcs (4x200 GB SSD
> ?) that it outweighs an extra 32 GB of RAM ?
>

More RAM is always faster, but striped SSDs are pretty fast too. I'd max out
the RAM on this sort of server, and then add L2ARC devices if needed.


>
> - provided I maintain the free pcie slot(s) and/or free 2.5" drive slots,
> can I always just add a ZIL after the fact ?  I'd prefer to skip it for now
> and save that complexity for later...
>

Yes, you can add a ZIL later.


>
> Thanks very much for any comments/suggestions.
>
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-- 
Joshua Boyd

E-mail: boydjd at jbip.net
http://www.jbip.net


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