Who Makes The Best RAID Controller? 24
thonot asks: "I build PC's from my home, generally for frinds and friends of friends. Yesterday though, my wife's boss called me and asked if I could build him a bussiness PC. The only problem is that he wants a RAID0 configuration w/ 3 Seagate Cheetah 18.4 Gig 15k RPM SCSI drives, and I've never even seen a RAID controller, well except in pictures. Can anyone point me in the direction of a good controller card?"
Re:Moratorium (Score:4, Insightful)
If you ban questions that an answer can be found on Google, then you'd pretty much have to drop askslashdot as a section. For instance, take the last three questions:
Colocation facilities in Southern California [google.com]
Xbox as a DVD player [google.com]
Office culture for IT employees [google.com]
I admit that I personally turn to Google first, but if the information one gets back is overwhelming, confusing, or contradictory, then I don't have a problem sending the question here.
Er, yes and no (Score:1)
A month from now I would probably consider the XBox question unsuitable as well.
Something like the RAID question is more suited for an IT version of Consumer Reports. E.g. Tom's Hardware [tomshardware.com] or AnandTech [anandtech.com], both of which he would find in a Google search along with many other far more useful pages (e.g. RAID HOWTO's
My 2c.
Re:Moratorium (Score:2)
Good experiences (Score:5, Informative)
With Mylex, you can get the controllers either as PCI cards for the box, or you can get one that comes as a big box (external controller).
The PCI version looks basically like a SCSI card, and is configured by software you get with it.
The external version is meant to be mounted in a separate tower with your drives. Often comes with its own memory and LCD screen and fun buttons to play with (and configure the array with). It has two (or more) connectors - one to the computer (entire array appears as a single SCSI ID) and one to the rest of the drives in their own SCSI chain. The advantage to the external model is that you only need to install the drivers for your SCSI card - the array requires no additional software. Disadvantage is that they require space in an external tower - often they are full height (2 bays).
With the Compaq beasties, you'd need the Compaq SmartStart CD that comes with their servers to configure the stupid arrays. Can't find the software on their site anywhere. But... they are good controllers and have never let me down.
One thing though - RAID 0 (striping) is a dumb configuration for business use. If any single drive dies, you lose all the information on ALL of them. RAID 0 basically chains the drives together to make one gigantic drive.
RAID 1 (mirror) offers you redundancy. One drive mirrors to another. But... that means you lose the capacity of one drive (and RAID 1 only supports 2 drives). If a drive dies, use the other one.
RAID 0+1 (stripe + mirror) for use with an even number of drives. Basically stripe as many drives together as you want, then mirror that entire array to another set of drives. You lose the capacity of half of your drives for the mirror. If a drive dies, you use the other chain.
RAID 5 is probably one of the most common configurations. Chain a few drives (most people do 3-5, but it supports more) and it distributes parity information throughout the array. If you lose a drive, you can replace it and keep going - no data loss. You lose the capacity of ONE drive in this configuration. Thus, it's less of a loss if you have 5 drives (20%) than if you have 3 (33%). It's perhaps not the fastest type of array around, especially for lots of seeks (it's fast for large files) - do not use RAID 5 for a database, for example.
All this being said, if all you need is striping (RAID 0), chances are that whatever OS you're using supports doing this in software quite nicely without much overhead at all. For example, NT and Linux both support software RAID 0 right out of the box.
If you MUST buy a controller, then Ebay is your friend.
Re:Good experiences (Score:3, Informative)
You used the notation that is probably more sensible, but your explanation is backwards.
RAID 10 (aka RAID 0+1) is a RAID 0 of RAID 1s. IOW it is two or more mirrored pairs, with striping across them.
You have also glossed over the difference between RAID 1 - mirroring and RAID 1 - duplexing, but then assumed we are talking about duplexing (when you said "other chain").
Duplexing is when you use two controllers. The advantage is, as you mention, if one controller fails, your other member is still accessable. The down side is that all data must cross the bus twice (ugh) and it is less seamless. (Imagine duplexing / (or
-Peter
Re:Good experiences (Score:1)
here's one for $30 (Score:4, Informative)
I bought one of these but haven't tried it yet. it won't be a super fast/modern one, but it should work ok.
I've had good luck with mylex DAC960 style controller. linux support is VERY stable with these. in fact, while mucking around inside my pc, I accidentally pulled out a 4wire molex power connector to one of my raid drives (oops!). doing a tail -f of /var/log/messages showed that the controller saw a drive go offline and started rebuilding the pack, all in the background, to a spare mounted raid drive! quite impressive.
given the price of hardware scsi raid controllers today, its hard to justify ide or software raid..
Re:here's one for $30 (Score:1)
Given the price of disks today, it is easy to justify IDE RAID.
Re:here's one for $30 (Score:3, Informative)
Looking at it another way - looking at how the price of SCSI drives has dropped (though still a premium above IDE, esp for 15krpm), the cost there isn't really all that bad.
Your average Joe might be more than thrilled with a RAID1/0 of 4 60GB IDE drives (mmmmmm, storage), but depending on your use, the price premium can be easily justified.
MegaRAID and RAID 0 (Score:4, Informative)
On an un-related note, think really hard before going with RAID 0 (or before implementing one for someone else).
I describe RAID 0 as "anti-RAID" since it provides "undundancy." Which is to say it significantly increases the chance of hardware failure related data loss. Why would you want this?
Of course the reason for RAID 0 is performance. So, if you literally can't do what you need to do without RAID 0, well, then, I guess you do what you have to do. But consider that RAID 5 is nearly as fast (on a HW RAID) as RAID 0. Yes, you pay a disk space penalty, but a good controller will let you add a disk an grow the array when you have nearly filled the drive (and disk prices are probably lower). If you can spend the bucks, and you really feel like you need the speed, build a RAID 10. You get some read advantage from the 1 over 0, and the write penalty will be minimal with a decent controller.
The only time I would recommend RAID 0 would be if you have a situation where 1. the data has another "perminant" home and 2. you are in a fix for speed or capacity on the array.
Good luck!
-Peter
Re: MegaRAID and RAID 0 (Score:2, Informative)
One quick comment... AMI [ami.com] recently sold their hardware RAID business to LSI Logic [lsilogic.com]. See this page [lsilogic.com] for LSI's RAID information.
FWIW, Adaptec. (Score:3, Informative)
It's fairly inexpensive, it does RAID0, 1, 0/1 and 5. It's single channel (all you need with 3 drives). It will take almost any EDO SIMM up to 64MB for it's cache. The only real downside is it only supports NetWare 4.11, 4.2, 5.0 SCO Unixware 7.0, and it's not hot-swappable. And the OS req. that's mainly for it's CIO Manager software, which only really alerts you when there is a failed drive. If you going to build a Win box, it's really the simplest choice.
Honestly, we have several years of use of these array controllers, never had one fail, never had one quit. In fact I've never had a problem with any of our Adaptec controllers.
Just my 2 cents though
Windows NT 4.0/2000
Re:FWIW, Adaptec. (Score:1)
The line starts with the single channel 2100s and goes up in capacity to the four channel 3410S. Just plug regular SCSI drives into them, use the BIOS mode or provided software to create RAID0, RAID1, RAID0+1, or RAID5 volumes, and your host operating system sees the volume as a single SCSI target.
Adaptec seem to be fairly open source friendly. Check out the Adaptec Open Source website [adaptec.com]. They provide drivers and software for both FreeBSD and Linux. It's nice to have software support for the controller so you don't have to boot into the BIOS to make a configuration change. The docs for the 'dpteng' and related tools was sparse, but I suspect most people could figure it out after a bit of farting around. I know FreeBSD includes support for the controllers via the 'asr' driver included by default in the GENERIC kernel. If the driver isn't in by default in your Linux distro, just download from Adaptec. They work splendidly under Windows 2000 as well, if you need that functionality.
Anyhow, just thought I'd share my experience with this relatively inexpensive controller from Adaptec. I have about 40 2100S and 4 3410S controllers in service, and they've been fine so far (and yes, I've had drive failures with them and done replacements without problems so far). They play well with the SCSI enclosure cards too, which is nice for hot-swap systems and "fancier" rack mount arrays.
On a FreeBSD system, you see:
asr0: mem 0xea000000-0xebffffff irq 11 at device 5.1 on pci1
asr0: ADAPTEC 2100S FW Rev. 3607, 1 channel, 256 CCBs, Protocol I2O
-Mark
Which OS do you plan to use? (Score:1)