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I'm building my first home NAS right now, and I have a Mini-ITX motherboard with 4 SATA connections. I'd like to connect 6 hard drives in total and (preferably) use software RAID.

My question is: Will a SATA expansion card allow me to use all of my SATA connections together in a software RAID configuration, or will I need to put the entire array on the motherboard or controller?

Blake
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To the best of my knowledge, you cannot combine motherboard SATA with an expansion card's SATA to create a single Hardware RAID set. But, consider that each drive is going to add about 30 watts draw at spinup. So, right there, that's about 180 watts for just the 6 drives. If you are using a Mini ITX board, you probably aren't using a large power supply... what... 160 watt at most? So, before trying to RAID across two different controller chips, power is going to be a major issue.

EDIT As Journeyman Geek points out, you should still be able to set up a software RAID. Which is what you asked about...

Software RAID has one further important distinguishing feature: it operates on a partition-by-partition basis, where a number of individual disk partitions are ganged together to create a RAID partition. This is in contrast to most hardware RAID solutions, which gang together entire disk drives into an array. With hardware, the fact that there is a RAID array is transparent to the operating system, which tends to simplify management. With software, there are far more configuration options and choices, tending to complicate matters.

Doing it across the expansion card bus will also affect performance.

Bon Gart
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  • He could, in theory use a full sized PSU with the right case, but even those usually don't have that many sata power connectors. He *can* use softraid in that scenario though, i think – Journeyman Geek Jun 13 '12 at 05:35
  • @JourneymanGeek good point. A software RAID would be OS dependent though and would affect performance. But that is an option. I'll edit for that. – Bon Gart Jun 13 '12 at 05:48
  • The question does say software raid, so, yeah, its in serious consideration i'd think – Journeyman Geek Jun 13 '12 at 05:54
  • @JourneymanGeek yeah, I felt like a schmuck for not putting more emphasis on that. Just didn't want the power issue to be overlooked. – Bon Gart Jun 13 '12 at 07:02
  • I have a 300W PSU, so that should (hopefully) support 6 harddrives without trouble. Thanks. – Blake Jun 13 '12 at 11:46
  • Use this http://extreme.outervision.com/psucalculatorlite.jsp PSU calculator and be honest when you do. I had to make some guesses regarding what you might have for components, and I came up with a 286 watt minimum, 336 watt recommended. Be honest, and don't underestimate. If anything, overestimate. – Bon Gart Jun 13 '12 at 17:38
  • You can get around the startup power problem by enabling staggered spinup. Most drives have a jumper for this and it causes them to not spin up until commanded to by the computer, which tells each drive to spin up one at a time instead of all at once. It makes booting take longer, but limits the inrush current. – psusi Jun 13 '12 at 18:55
  • @psusi how would that work in combination with a 6 drive software raid set? Don't all the drives have to get detected and be spun up together, since they are all part of the same array? – Bon Gart Jun 13 '12 at 22:12
  • @BonGart, if it is software raid, then the the drives will spin up when the OS goes looking for them, if the bios hasn't already taken care of it. – psusi Jun 14 '12 at 00:45
  • @psusi ... and if the OS is installed on the array? – Bon Gart Jun 14 '12 at 00:47
  • @BonGart, then the bios needs to spin it in order to find the boot loader. Mine seems to do that though I wish it wouldn't since my OS is on an SSD and it is my old HDs that I rarely use now that I like to keep spun down. – psusi Jun 14 '12 at 00:53
  • @psusi see, I didn't know if with a software raid ( creating one big drive from a bunch of small ones), what was necessary to mount the Raid would be saved to one drive on a small partition first or not... so that just one drive would have to spin up at boot. – Bon Gart Jun 14 '12 at 01:07
  • @BonGart, that depends on your OS and how you have it set up. Windows isn't capable of booting from software raid, so you *have* to install it to a single drive, then soft raid the others. Linux can boot directly from software raid, or if your bios doesn't know how to spin up the disks, you can setup a /boot partition on just one that isn't configured for staggered spinup. – psusi Jun 14 '12 at 01:09