I've been recommended to look into building a custom FreeNAS box for storage so I can have 2 redundant VM hosts with the machines being stored externally for failover. I noticed in the forums that a lot of people are using raid controller cards. I was planning on using ZFS as past experience with hardware raid cards is expense but worse if they die you have to quickly get an equivalent card to rebuild. Why are so many using raid cards with FreeNAS? Isn't there a cheaper option for ZFS? I do understand you don't have to use the raid card as a raid but isn't using the motherboard sata connectors with 6 ports just as good when using ZFS? Is it safe to mix mb sata with a separate controller card?
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raid controller with zfs?
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jgreco
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Feel free to share with us how you're going to attach 8 (or more!) drives to four or six SATA ports on a motherboard.
Cheap SATA controller cards are, by design, generally a bit dodgy. No fun to lose your data; if you're spending hundreds or thousands of dollars on drives, and designing a NAS system with RAIDZ2 to ensure the safety of your data, it makes sense to avoid using a cheap SATA card, even though it might work just fine. To get the port densities required for a 24-drive SATA system, RAID controllers become a very attractive and economical way to go, giving the motherboard full access to each drive without a bandwidth-strangling port multiplier or something like that sitting in there messing things up.
With the recommended RAID cards, you do not necessarily need to get an "equivalent" card to rebuild; the purpose of running these things in SATA mode is that the attached storage is presented to the OS as though it was just a large multiport SATA card. Cards like the M1015 are cheap enough that you can spare one, anyways, because the reality is that even if the disk is just passed through, it's damn inconvenient to have to figure out how to hook up a bunch of drives without a card that made the port density reasonable in the first place, and little gotchas like cabling are always a nuisance.
Generally(!) speaking, your FreeNAS ZFS system isn't going to care whether your drives are attached to a controller like the M1015 or your motherboard ports. However, please beware that there are sometimes design issues that can affect things. Let's say you've got a stupid motherboard with four SATA-II ports behind a legacy PCI bridge. You'll find that you may not be able to get full bandwidth of your disks out of those ports. Or a dodgy SATA controller chipset on the motherboard? These things can and do happen. Using a controller that was designed to be "server" class (even if just low-end server class) reduces the number of things that might go wrong, and sometimes people just like uniformity as well.
Cheap SATA controller cards are, by design, generally a bit dodgy. No fun to lose your data; if you're spending hundreds or thousands of dollars on drives, and designing a NAS system with RAIDZ2 to ensure the safety of your data, it makes sense to avoid using a cheap SATA card, even though it might work just fine. To get the port densities required for a 24-drive SATA system, RAID controllers become a very attractive and economical way to go, giving the motherboard full access to each drive without a bandwidth-strangling port multiplier or something like that sitting in there messing things up.
With the recommended RAID cards, you do not necessarily need to get an "equivalent" card to rebuild; the purpose of running these things in SATA mode is that the attached storage is presented to the OS as though it was just a large multiport SATA card. Cards like the M1015 are cheap enough that you can spare one, anyways, because the reality is that even if the disk is just passed through, it's damn inconvenient to have to figure out how to hook up a bunch of drives without a card that made the port density reasonable in the first place, and little gotchas like cabling are always a nuisance.
Generally(!) speaking, your FreeNAS ZFS system isn't going to care whether your drives are attached to a controller like the M1015 or your motherboard ports. However, please beware that there are sometimes design issues that can affect things. Let's say you've got a stupid motherboard with four SATA-II ports behind a legacy PCI bridge. You'll find that you may not be able to get full bandwidth of your disks out of those ports. Or a dodgy SATA controller chipset on the motherboard? These things can and do happen. Using a controller that was designed to be "server" class (even if just low-end server class) reduces the number of things that might go wrong, and sometimes people just like uniformity as well.
Thanks for the info I'll make sure I don't mix onboard sata with controller cards then if that dampers performance. However, I was thinking of finding a board with 6 sata3 ports and using 6 500 GB drives in a zraid2. Is this a bad idea? If so I'll just buy the controller.
jgreco
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It's not necessarily a bad idea. Many boards have good-to-great onboard SATA support. If you have a board with a bunch of SATA-III ports, at least right now, that means that the board is aimed at more demanding users, and my impression is that it's more likely to have a good design. In three or four years, when SATA-III is the old cruddy interface, though, expect that implementations may be more dodgy.
Of course, I make no promises as to the quality of any particular SATA implementation, my note was merely to stress that a board that is specifically designed for hard drive expansion should be among the most reliable of all options. If you read what others have posted here and elsewhere, and pay particular attention to problem reports that don't sound like a third-grader wrote them, you should be able to find good information on options that work well, and also options that might be more troublesome. Doing research is always recommended.
Of course, I make no promises as to the quality of any particular SATA implementation, my note was merely to stress that a board that is specifically designed for hard drive expansion should be among the most reliable of all options. If you read what others have posted here and elsewhere, and pay particular attention to problem reports that don't sound like a third-grader wrote them, you should be able to find good information on options that work well, and also options that might be more troublesome. Doing research is always recommended.
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