Today I received a commecial offer on some external USB 3.0 disk enclosure. Since it was new to me I googled my way to wikipedia and found that the specs say USB 3.0 should have a 5 Gbit speeds capability. I visited newegg and found out that a 2-port USB3.0 HBA is sold for 40$ and I also tried to search a USB 3.0 switch/hub, however did not find any yet. Since the small formfactor mobile drives could even receive power over their USB cable; this could be a interesting addtional feature. Could it be an interesting solution to build a very cheap storage area network? ( Ofcourse ZFS in the middle to manage the shares. ) Or is this wishfull (e.g. bad) thinking? Kind regards, Armand This directly made me thinking and I googled a 5 port -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://mail.opensolaris.org/pipermail/zfs-discuss/attachments/20100222/cd3d0ad7/attachment.html>
On Feb 22, 2010, at 9:46 AM, A. Krijgsman wrote:> Today I received a commecial offer on some external USB 3.0 disk enclosure. > Since it was new to me I googled my way to wikipedia and found that the specs say > USB 3.0 should have a 5 Gbit speeds capability. > > I visited newegg and found out that a 2-port USB3.0 HBA is sold for 40$ and > > I also tried to search a USB 3.0 switch/hub, however did not find any yet.Not surprising... it is still very new.> Since the small formfactor mobile drives could even receive power over their USB cable; > this could be a interesting addtional feature.This was true of USB 1.0 also. Quite a few USB 2.0 drives are powered from USB (a good thing :-)> Could it be an interesting solution to build a very cheap storage area network? > ( Ofcourse ZFS in the middle to manage the shares. ) Or is this wishfull (e.g. bad) thinking?It all depends on if the USB disk honors cache flush commands. -- richard ZFS storage and performance consulting at http://www.RichardElling.com ZFS training on deduplication, NexentaStor, and NAS performance http://nexenta-atlanta.eventbrite.com (March 15-17, 2010)
On Feb 22, 2010, at 18:02, Richard Elling wrote:> On Feb 22, 2010, at 9:46 AM, A. Krijgsman wrote: > >> Today I received a commecial offer on some external USB 3.0 disk >> enclosure. >> Since it was new to me I googled my way to wikipedia and found that >> the specs say >> USB 3.0 should have a 5 Gbit speeds capability. >> Could it be an interesting solution to build a very cheap storage >> area network? >> ( Ofcourse ZFS in the middle to manage the shares. ) Or is this >> wishfull (e.g. bad) thinking? > > It all depends on if the USB disk honors cache flush commands.''Cheap'' is the keyword - you get what you pay for. I found with some USB drives that ZFS scrubs were showing hundreds of checksum errors, so I ditched the drives straight away. The problem is more the firmware rather than the interface itself; but you won''t know until you find it. On the other hand, I''ve not found drives with FireWire 800 support to have problems, and in any case, FW800 has a better real-world throughput than USB2. By the time you go much above it, you end up with a single drive''s spindle being the bottleneck rather than the bus - though of course, multiple drives will start to fill up a bus anyway. It''s worth noting that USB leeches control from the host computer, so even if the bandwidth is there, the performance might not be for several competing drives on the same bus, regardless of how big the number is printed. Here''s some (old) analysis of ZFS and HFS on USB and firewire: http://alblue.blogspot.com/2008/04/review-iomega-ultramax-and-hfz-vs-zfs.html How much that translates over to USB 3, I don''t know, but there''s a difference between ''theoretical'' and ''practical''. It would be good to see what kind of performance numbers you can come up with, or if you run into the same kind of problems with USB that existed for slower models. (Sadly, the planned FW3200 seems to have disappeared into a hole in the ground.) Alex
On Feb 22, 2010, at 13:20, Alex Blewitt wrote:> It''s worth noting that USB leeches control from the host computer, > so even if the bandwidth is there, the performance might not be for > several competing drives on the same bus, regardless of how big the > number is printed.The other thing to consider is that historically USB has sucked a lot of CPU since the controllers are fairly dumb (we''ll see about 3.0 though). Now we all supposedly have CPU to spare, but depending on what else the system is doing, it may have an impact. And that 4 Gb/s is the raw bandwidth of the bus; protocol overhead will bring that down (Wikipedia says down to 3.2 Gb/s). On Feb 22, 2010, at 12:46, A. Krijgsman wrote:> Could it be an interesting solution to build a very cheap storage > area network? > ( Ofcourse ZFS in the middle to manage the shares. ) Or is this > wishfull (e.g. bad) thinking?It may be useful for something like "tier 2" storage where you keep a back up copy of your data (via zfs send-recv?), but I wouldn''t put homedirs or a mail spool on it. There are probably plenty of decently priced eSATA or SAS enclosures that would probably be a better option. If you can get a good deal, it may be okay for a "lab machine" to play around with though.