zfs discuss - Aug 2007 - It is that time again... ZFS + Firewire/USB - and a specific enclosure

I am looking into getting something like this:
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&rd=1&item=120069356632&ssPageName=STRK:MEWA:IT&ih=002

For a home storage server. I would like to run ZFS. Preferrably
FreeBSD (if basic functionality is completely bug-free and I won''t
lose any data :)) as I am more comfortable with it.

However, I have been subscribed to the ZFS lists for some time now and
done a Google check up for topics relating to this for some time, and
the jury still seems to be out on whether or not this would be a good
idea.

I need it mainly for DVD storage (for easy playback) and personal
archiving. So maybe 3-4 read streams and 1-2 write streams - probably
at peak time.

Is this a viable option? I want capacity more than speed; but I want
at least single parity redundancy with RAID-Z. Would it be an option
to add 8 drive units as needed, making them each a single RAID-Z
device (so 7 drives usable?) and add them into the same zpool to
increase available storage when I would get low?

I might be missing some concepts here... but I keep querying this list
hoping someone has done some of the footwork already (I don''t have as
many funds available to me as in the past to mess around with
experimental/untested ideas) not to mention I don''t want to be
experimenting with my data... or maybe someone at least has some
advice. I have seen a couple comments about Firewire, not many about
USB. I don''t care about the hotplugging, I can power down to replace
any drives or do maintenance. It''s mainly for cheap, quiet enclosures
that can export JBOD...

Thanks,
mike

> However, I have been subscribed to the ZFS lists for some time now and
> done a Google check up for topics relating to this for some time, and
> the jury still seems to be out on whether or not this would be a good
> idea.
My only input is that when I used cheap-ass USB enclosures (for single disks) 
flush-cache commands never survived. i would get errors about unimplemented 
SCSI commands upon every ZFS transaction group commit. So a no-go for 
reliability (unless you can turn write caching off "through" the USB 
conversion - dunno, but even then you will instead suffer the performance 
penalty).

I don''t know whether this was because of USB, or because it was
cheap-ass
crap, or something else. Perhaps Firewire works better, especially 
considering it was the de de facto standard in Macs for a long time.

The other issue is that I never seem to get decent performance out of USB, and 
in general have experienced USB enclosures and even USB hubs to be very buggy  
(randomly breaking, particularly with I/O happening with multiple devices at 
the same time, and then requireing power cycling to start working again).

I started buying USB drives at one point to get around the problems with 
fitting many disks in consumer products (=stuff that doesn''t cost
$1000000),
but eventually just gave up because of broken drive controllers (hello WD) 
and broken USB hardware. And don''t think that a retailer will consider 
drives "broken" for the purpose of warranty when they exhibit
identical
problems on both Solaris and FreeBSD (with AFAIK independent USB 
implementations), but work in Windows...

If you have luck with that then please post some public info as I am sure I 
would not be the only one to be interested in it. Wonder what those 8-ways 
cost new...

-- 
/ Peter Schuller

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