On Fri, Feb 25, 2011 at 4:34 PM, Rich Teer<rich.t...@rite-group.com> wrote:
Space is starting to get a bit tight here, so I'm looking at adding
a couple of TB to my home server. I'm considering external USB or
FireWire attached drive enclosures. Cost is a real issue, but I also
I would avoid USB, since it can be less reliable than other connection
methods. That's the impression I get from older posts made by Sun
devs, at least. I'm not sure how well Firewire 400 is supported, let
alone Firewire 800.
You might want to consider eSATA. Port multipliers are supported in
recent builds (128+ I think), and will give better performance than
USB. I'm not sure if PMP are supported on Sparc though., since it
requires support in both the controller and PMP.
Consider enclosures from other manufacturers as well. I've heard good
things about Sans Digital, but I've never used them. The 2-drive
enclosure has the same components as the item you linked but 1/2 the
cost via Newegg.
The intent would be put two 1TB or 2TB drives in the enclosure and use
ZFS to create a mirrored pool out of them. Assuming this enclosure is
set to JBOD mode, would I be able to use this with ZFS? The enclosure
Yes, but I think the enclosure has a SiI5744 inside it, so you'll
still have one connection from the computer to the enclosure. If that
goes, you'll lose both drives. If you're just using two drives, two
separate enclosures on separate buses may be better. Look at
http://www.sansdigital.com/towerstor/ts1ut.html for instance. There
are also larger enclosures with up to 8 drives.
I can't think of a reason why it wouldn't work, but I also have exactly
zero experience with this kind of set up!
Like I mentioned, USB is prone to some flakiness.
Assuming this would work, given that I can't see to find a 4-drive
version of it, would I be correct in thinking that I could buy two of
You might be better off using separate enclosures for reliability.
Make sure to split the mirrors across the two devices. Use separate
USB controllers if possible, so a bus reset doesn't affect both sides.
Assuming my proposed enclosure would work, and assuming the use of
reasonable quality 7200 RPM disks, how would you expect the performance
to compare with the differential UltraSCSI set up I'm currently using?
I think the DWIS is rated at either 20MB/sec or 40MB/sec, so on the
surface, the USB attached drives would seem to be MUCH faster...
USB 2.0 is about 30-40MB/s under ideal conditions, but doesn't support
any of the command queuing that SCSI does. I'd expect performance to
be slightly lower, and to use slightly more CPU. Most USB controllers
don't support DMA, so all I/O requires CPU time.
What about an inexpensive SAS card (eg: Supermicro AOC-USAS-L4i) and
external SAS enclosure (eg: Sans Digital TowerRAID TR4X). It would
cost about $350 for the setup.
-B
