Order Code SR1500AL w/Passive Backplane1(No Midplane) SR1500ALSAS  w/Active Backplane2 (No Midplane) SR2500ALBRP  w/Passive Midplane1 SR2500ALLX  w/Active Midplane2 SR1550AL w/Passive Midplane1 SR1550ALSAS  w/Active Midplane2 Hot-swap hard drives support 3x 3.5” 3x 3.5” 5 standard, 6 optional – 3.5” 5 standard, 6 optional – 3.5” 6 standard, 8 optional – 2.5” 6 standard, 8 optional – 2.5” Hard drive interfaces supported SATA (or SAS via add-in card) SATA or SAS SATA (or SAS via add-in card) SATA or SAS SATA (or SAS via add-in card) SATA or SAS Storage controller SATA from the Intel® 5000P/5000X chipset SAS controller on backplane SATA from the  Intel® 5000P/5000X chipset SAS controller on midplane (option for IOP-based HW RAID5) Up to 6 SATA from the Intel® 5000P/5000X chipset SAS controller on midplane (option for IOP-based HW RAID5) Optical / Tape drive bay(s) One slim optical One slim optical One slim optical plus tape option One slim optical plus tape option One slim optical One slim optical Power 600W 600W 750W 1+0 750W 1+0 650W 1+0 650W 1+0 Add-in card support 1 FH (PCIe or PCI-X), 1 LP (PCIe only) 1 FH (PCIe or PCI-X), 1 LP (PCIe only) 3 FH, 2 LP (FH = PCIe or PCI-X, LP = PCIe only) 3 FH, 2 LP (FH = PCIe or PCI-X, LP = PCIe only) 1 FH (PCIe or PCI-X), 1 LP (PCIe only) 1 FH (PCIe or PCI-X), 1 LP (PCIe only) System fans 5 Non redundant 5 Non redundant 3 Non redundant 6 Redundant & hot swap standard 5 Non redundant 5 Non redundant

Note: 
¹ - Passive Midplane and Backplane are all using direct SATA cables routing from the server board or add-in SAS/SATA controller
² - Active Midplane and Backplane have a sas controller onboard which communicates directly with the drives, and can therefore NOT support add-in sas/sata controllers

This applies to:

Intel® Server Board S5000PAL