SATA (Serial ATA) or SCSI?
Traditionally, serious folks have always preferred SCSI disks. These people are concerned about mission critical applications. However, the price of SCSI disks is far higher than for Serial ATA disks. It's important to recognise when one solution (SATA) is better value for your application than the other.
The gating question according to this article is 'How transactional is the pattern of access to your disks?' If it's highly transactional, then you probably want a SCSI disk. However, if it's just a lot of sequential access, Serial ATA may be just the ticket. After all, with the large price difference, even if SATA disks have a lower mean-time-before-failure, you can buy more of them and increase your redundancy and still end up in front.
There is also a reliability/data integrity issue. In this article, the author argues that SATA disks, because of their write-back caching and reordering, fare worse in the event of a power failure than their SCSI counterparts. This seems like a valid criticism; though the price difference between SCSI and SATA is still compelling for many applications.
Linux Software RAID and Hardware RAID
Linux provides a native software RAID. This allows you to use the system processor and a few disks to create a RAID array without resorting to buying a specialized controller. Adaptec has written a few words about this, here . I don't agree with their argument that hardware RAID brings higher performance- any argument like that really needs to be couched with some discussion of the price difference involved- good hardware RAID controllers are not cheap, and using this extra money, to say, buy a machine will extra processors, might, for all I know, improve the performance enough to offset the dedicated RAID processor.
A much better argument (which they also make) is reliability. Transactions with a hardware RAID array can complete in situations where the host has crashed. Battery backup of the transaction cache gives better data integrity. I think this is a much more solid argument.
If you are interested in simply striping your data, reliability isn't as important; it's all about speed. That may mean that software RAID is the option for you.
Linux Hardware RAID
RAID controllers can either process data primarily on the host, or do it themselves. This substantially changes the price. The reliability argument doesn't hold for the host based solutions, since a system crash will lose data more easily than the equivalent hardware solution. The moral of the story is that host based RAID probably doesn't offer you a great deal over regular software RAID- they might be cheap, but you're not really buying anything as far as I can see. (If somebody could point me to something which explains any more advantages of host-based architectures, that would be good! This is still a document-in-progress! Email me).
Adaptec 1420SA
Adaptec has great mindshare in the RAID world. But before you buy, be sure to check out what Brent Norris had to say about their support. The gist is that although you may well pick Adaptec for a SCSI solution, you probably don't want to know about this card if you're after SATA.Adaptec Adaptec 2410SA
A few sites say the performance of this card is sucky. Check for example this page which blames the lacklustre performance on the IOP302/IOP303 chipsets used by this family. If you're a bit lost with the differences between the available chipsets, this page is a fairly complete account of the different controllers about.
Adaptec 2420SA
Does SATA-ii, Linux compatible. A big improvement over the other Adaptec cards, and has an SRP of $375US. No drivers to download, kernel support in linux. :) A good card.
Areca ARC-1120
An awesome card. Look at the clockrate on the onboard IOP and compare it to what Intel did with their server boards to see what I mean. This thing was built to fly, but unfortunately it comes with a hefty price-tag... (Maybe because of their small production numbers?!?). It's of course, real hardware RAID, and does SATA-ii. This was my pick until I found the MegaRAID SATA 300-4X (below) which is miles cheaper for the same performance.
Areca ARC-1210
This is a new card from Areca. It features an Intel IOP333 controller, 256MB of DDR333 ECC RAM.3ware Escalade 8506-4
A tweakers.net review didn't like the I/O performance of this card's 8-port sibling. The gist is that the 3ware Escalade 9500S-4 would probably be preferred.
3ware Escalade 9500S-4
128Mb cache default, the big brother of the 8506-4.
3ware 9550SX
This is the newest 3ware card I've found. The specifications are impressive. It will do 800MB/sec reads in RAID 5. It will do 380MB/sec writes in RAID 5. It's more than twice as fast as the previous 3ware 95000S. Check out this brief review here. It takes up to 256MB of DDR2-400 ECC RAM.
HighPoint RocketRAID 1640
I don't understand why anybody would buy this card. Check out this review. The reviewer is very kind - if you jump to the conclusion, you'll notice the card doesn't seem to give much of an advantage for the money. Again, if there are any positive attributes that I'm missing, let me know! :)
ICP Vortex
ICP Vortex GDT8586RZ and GDT8546RZ. The same arguments made for the Adaptec above have been made against these Vortex cards. Expensive, underperformers.
MegaRAID SATA 300-4X, Megraid SATA 300-8X
This post suggests people are very happy performance wise with this line of cards. They've encountered a few problems installing; but look to be well supported past Linux kernel 2.6.10. This card is very comparable to the Areca, but available much more cheaply. Buy this card. These people sell the 8 port card cheaper than the 4 port card at some other places. Incidentally, it also works with FreeBSD using the amr driver... :)
Promise FastTrak S150 SX4-M
This card has RAID accelerator functions, but requires software support. This means that when you see a writeup, the writer typically dances around the point of whether it's actually real hardware RAID. Under Linux, according to this page , the acceleration features aren't used by linux, although it will function.
RAIDCore BC4452
Binary only drivers for specific distros... No source... At this point, I abandoned my review of this card.... ;) This isn't for religious reasons but for practical reasons. In my living room there is a machine with a similar binary only driver. It boots kernel 2.4.10. Why 2.4.10? Because that's the only kernel that supports it's ADSL binary-only kernel module. That's the last binary only product that I'll have anything to do with. Binary only sucks.
Summary
| Adapter | Linux Source Code Available? | Real RAID or Fakeraid? |
|---|---|---|
| Adaptec 2410SA | Yes | Real Hardware RAID |
| 3ware Escalade 8506-4 | Yes | Real Hardware RAID |
| 3ware Escalade 9500S-4 | Yes | Real Hardware RAID |
| 3ware Escalade 9550SX | Yes | Real Hardware RAID |
| Tekram Areca ARC-1110 | Yes | Real Hardware RAID |
| MegaRAID SATA 300-4X | Yes | Real Hardware RAID |
| Promise FastTrak S150 SX4-M | No | Fakeraid |
| RAIDCore BC4452 | No | Fakeraid |
| ICP Vortex | Yes | Real Hardware RAID |