On Fri, 11 May 2007, Sophia Li wrote: > >>>> -------- Original Message -------- > >>>>On 5/10/07, Al Hopper <[EMAIL PROTECTED]> wrote: > >>>> > >>>>> My personal opinion is that USB is not robust enough under (Open)Solaris > >>>>> to provide the reliability that someone considering ZFS is looking for. > >>>>> I base this on experience with two 7 port powered USB hubs, each with 4 > >>>>> * > >>>>> 2Gb Kingston flash drives, connected via 2 ports to a Solaris (update 3) > >>>>> desktop box which runs ZFS on two internal 500Gb drives. I see about 24 > >>>>> to 28Mb/Sec (bytes) maximum of bandwidth over each USB bus. One time, > >>>>> after disconnecting one hub (to show someone the hub with 4*USB drives) > >>>>> it > >>>>> hung the OS and reset the box. A subsequent import of the ZFS volume > >>>>> that > >>>>> was disconnected, failed. (Yes it was exported, but failed to import). > >>>>> So my take on USB is ... it's not sufficiently robust - and a USB > >>>>> related > >>>>> failure is likely to cause loss of the entire ZFS dataset; i.e., its > >>>>> likely to trash more that one drive in a raidz config. > > I am interested in your this comment on USB. But it seems too general > and not helpful to solve problems. Several issues have been mixed > together which may not necessarily be USB's fault. If you believe there
Agreed. > is a USB issue, a better practice is to file a bug. And please make sure > the problem is reproducible and be detailed in problem description. :-) Understood. > I play with USB devices a lot and seldom see hotplugging hangs a system. > The hang looks very exceptional to me. Could you experiment more with > the devices and combinations of filesystem configuration? e.g., if you > put on the drives UFS instead of ZFS, would it hang? Is there a way that > you can reproduce the hang much more reliably? I really can't experiment with this particular machine, because its my main desktop that drives a 22" and 30" LCDs, has about 18 Gnome workspaces and 80+ windows active. If the Xserver dies it take 10 to 15 minutes just to get everything setup again so that I can get my productive development environment in place. And that is aside from the ZFS mirrored pool on the machine that has 45+ filesystems and 6 zones defined. So - experimenting with it is not possible for now. ... more below ... > Another question is if you are using ZFS on USB drives, the system hangs > due to non-usb related reason and you reset the box, can data integrity > on the USB drives be ensured? > > Yet another question is if you are using non-USB drives, the system > hangs due to whatever reason and you reset the box, can data integrity > on the non-USB drives be ensured? And how, by SW or HW? > > We need to think of the questions and make clear if such kind of data > loss is particular to USB or not before coming to a conclusion too quickly. The only conclusion I've reached is that attaching 6 or 8 750Gb disk drives via USB for use as ZFS pool is not a good idea - because USB is not robust enough to guarantee, that in the event of a USB failure or "event", that no more than one disk configured in a raidz configuration will be negatively impacted. If more than one disk drive in a raidz storage pool is negatively impacted, then you'll loose the entire pool. USB is not an appropriate bus to support that type of usage scenario IMHO. USB is fine as a demonstrator of ZFS capabilities by connecting multiple USB flash drives (as I've done) and can also be used as a way to archive files reliably on a removable media (the flash drives). And using ZFS with flash drives solves the problem of corrupted or bad sectors on low-cost flash drives - which may or may not have been 100% tested before they were sold. > > >>>> > >>>>> I'd be interested in hearing other opinions on USB connected drives > >>>>> under (Open)Solaris .... > >>>> > > Any bus can have errors. USB is nothing particular, just the chance of > encountering errors is bigger since USB device is cheap. But isn't the Every bus topology has appropriate and inappropriate uses - and USB is no exception to that rule. > file system expected to handle possible errors? see above. Regards, Al Hopper Logical Approach Inc, Plano, TX. [EMAIL PROTECTED] Voice: 972.379.2133 Fax: 972.379.2134 Timezone: US CDT OpenSolaris Governing Board (OGB) Member - Apr 2005 to Mar 2007 http://www.opensolaris.org/os/community/ogb/ogb_2005-2007/ _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss