July 27, 201114 yr I am getting a motherboard with the onboard LSI SAS2008 controller on it and will have less then 8 drives to begin with. Can I plug the SAS 2008 controller directly into the backplane, set up unRAID, and then sometime in the future add an Intel RES2SV240 SAS expander (SAS 2008 to Intel SAS expander to the drives)? The drives would be moved from being directly plugged into the controller to being plugged into the Intel SAS expander. Will unRAID handle this and just recognize the new arrangement of drives?
July 27, 201114 yr I don't know the answer to your question, but madburg and the others active in this thread probably do!
July 28, 201114 yr Even if it does work you'll only be able to run 16 drives at full speed on a PCIex4 slot. Parity build/check, disk rebuild, and failed disk simulation will be slow. And why move drives off of the MB SATA ports rather than adding additional drives to expander? Keep the drives currently on the MB SATA ports as is and the add up to 16 additional drives to the expander.
July 28, 201114 yr Author All LSI SAS2008 controllers I know about, both in onboard and card form, are PCIe 2.0 x8. Should give 3Gbps (384MB/s) per drive (6Gbps x 8 channels / 16 drives). Just looking to postpone buying the RES2SV240 SAS expander until after I have 8 drives. According to Rajahal's comments here: http://lime-technology.com/forum/index.php?topic=13094.msg124220#msg124220 it doesn't look like it will have any ill effects, since unRAID goes by serial number and adding the SAS expander at most will change the drive location ID. This is a new build. Motherboard is a SuperMicro X8DTH-6F, bandwidth will not be a problem.
July 28, 201114 yr The expander you referenced is PCIex4. Recommended number of rotating magnetic media drives per PCI type: PCI: 1, PCIeX1: 2, PCIeX4: 8, PCIeX8: 16, PCIeX16: 32. Double these numbers for PCIe 2.0. The SATA speed of the drive is not important. A drive will not saturate even SATA I speed (1.5Gbps). Faster SATA speeds can be used for SATA-SATA port multipliers, e.g. eSATA drive bay with multiple drives. The main issue with this expander will be driver support.
July 28, 201114 yr Author The PCIe card edge on the expander is only for physical mounting and power. It can be screwed to the side of the case and powered through the molex plug (ie, not plugged into the motherboard). There are no drivers, it is an invisible/silent device. It is similar to the SATA-SATA port multipliers you mentioned, only at a whole different level of speed and features.
July 28, 201114 yr I see. So this will let you add up to 4 drives per SATA 6Gbit/s or 2 per SATA 3Gbit/s. It should work.
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