On Thu, Jul 16, 2009 at 17:02, Adam Sherman<asher...@versature.com> wrote: > Hello All, > > I'm just starting to think about building some mass-storage arrays and am > looking to better understand some of the components involved. > > For example, the Supermicro SC826 series of systems is available with three > backplanes: > > 1. SAS / SATA Expander Backplane with single LSI SASX28 Expander Chip > 2. SAS / SATA Expander Backplane with dual LSI SASX28 Expander Chips > 3. SAS / SATA Direct Attached Backplane > > Assuming I am using this an external array, connected to a server via SAS, > how do these fit into my topology? Expander, dual-expanders and no expander? > Huh? The "direct attached" backplane is right out. This means that each drive has its own individual sata port, meaning you'd need three SAS wide ports just to connect the drives.
The single-expander version has one LSI SAS expander, which connects to all the drives and has two "upstream" ports. This means you plug in one or two servers directly, and they can both see all the disks. I've only tested this with one-server configurations. It also has one "downstream" port which you could use to daisy-chain more expanders (i.e., more 826/846 cases) onto the same server. We have a SC846E1 at work; it's the 24-disk, 4u version of the 826e1. It's working quite nicely as a SATA JBOD enclosure. We'll probably be buying another in the coming year to have more capacity. The dual-expander version has two LSI SAS expanders. You need dual-port SAS drives (not SATA). This lets you have two paths all the way to each drive; even if one expander fails (this seems pretty unlikely to me, but if you're shooting for many nines it's worth considering) you still have access to the disks. > Thanks for pointing to relevant documentation. The manual for the Supermicro cases [1, 2] does a pretty good job IMO explaining the different options. See page D-14 and on in the 826 manual, or page D-11 and on in the 846 manual. Will [1]: http://supermicro.com/manuals/chassis/2U/SC826.pdf [2]: http://supermicro.com/manuals/chassis/tower/SC846.pdf _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
