On Sun, Feb 8, 2009 at 3:38 PM, Linda Walsh <lkml@xxxxxxxxx> wrote: > Is there something different, from normal disk-access, that I need to do > to access hard disks beyond '1', on a port-multiplier? > > I thought I remembered reading the port multiplier support was > working for many SATA and SATA RAID controller capable chipsets, > including the Sil 3124. > > I picked up a 2-Bay external SATA enclosure that I'm trying to access in > (what I thought) was the simplest mode: "JBOD". However, when I boot, > I am only seeing the first hard disk. > > Experimenting, I tried a single hard disk in both positions -- one > position let me see the disk directly (as though it was a direct, > str8-thru connection), the other position showed up detected by > the boot BIOS as a 7MB HD by some unrecognized vendor. In > linux, I'm able to access and use the hard disk when it appears > 'str8-thru', but linux sees nothing concerning the 7MB pseudo HD. > > Is my expectation that the driver would simply recognize the > external enclosure by whatever I had the external enclosure set to, > too optimistic? Do I need to run some special util to setup the disks in > JBOD mode? I guess I thought I only needed to worry about > 'special utils' if I was using the disk-pair in a RAID config (0/1)... > > It seems there should be a linux util to manage the "container", > 'sil57xx' -- I take it is not used for RAID-only config? > > My ultimate aim is to use it in a RAID-0, mirror config (my luck > with SATA disk drives has been abysmal, of late (*sigh*)). I assume you mean raid-1. I'm seeing a lot of people lose data even with that. There seem to be a lot of firmware specific bugs recently (not just seagate). Be sure and mix vendors / batches / etc. in an effort to keep away from near simultaneous double disk failure. > Anyone with any real-world experience about when the 3Gb SAS > starts to become a bottleneck? I know that theoretically, it could > support a hair over 350MB/s if there was no overhead, which would > reliably only support 2 hard disks at full speed (assuming ~120MB/s > max linear read speed/disk). In my real world tests I've never seen a single drive achieve beyond about 80MB/sec. (5GB/min is the way I actually measure it. That was using SATA directly on the MB which I assume is as fast a PCIe.) But very few people have a heavy linear read / write load (I do, but my use case is unusual). Most apps use random i/o. That is where raid in general should shine. That includes a PMP setup I assume. > Does that jive with people's real-world > experience? I.e. port-multipliers can provide full throughput for > 2-HD's but not likely 3? > Should I be looking for an sil57xx program somewhere (the box contained > a mini-CD, but it looks like a driver for an older kernel (2.6.9). Not so > sure about it's usefulness in my setup. > > Thanks, > -linda > > -- > To unsubscribe from this list: send the line "unsubscribe linux-ide" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > -- Greg Freemyer Litigation Triage Solutions Specialist http://www.linkedin.com/in/gregfreemyer First 99 Days Litigation White Paper - http://www.norcrossgroup.com/forms/whitepapers/99%20Days%20whitepaper.pdf The Norcross Group The Intersection of Evidence & Technology http://www.norcrossgroup.com -- To unsubscribe from this list: send the line "unsubscribe linux-ide" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
