To RAID or not to RAID

[Tannin]

I've never managed to get too interested in RAID, preffering to just run a motely collection of SCSI drives and try to spead the workload as evenly between them as I can. In fact, I barely read any of the RAID threads on SR and so far as I can remember have never so much as seen a system that has a RAID array.

My question is this: is there any reason I should go RAID in any of my own systems, or consider it for customer's systems? The apps I run are not performance-demanding, mostly standard desktop stuff: accounting package, spreadsheet, web browser, and associated things. (Why am I interested in performance you ask? Because I like things to happen right now, I hate waiting for the computer.)

So, bearing in mind that my two main systems are both Athlon XP 1700s, and that both have an X-15 Classic as their main drive, plus an older 7200 RPM SCSI drive as a spare, what benefit would I get from, say, grabbing a pair of shiny new IDE drives and RAIDing them?

 

[CougTek]

My question is this: is there any reason I should go RAID in any of my own systems,...

Do-it-yourself is the best way to learn about something. Messing a bit with a few RAID arrays would allow you to look more intelligent when one of your customers will pop up in your store and ask you something about RAID. It always shows when someone has only theoric knowledge about something and when he really knows what he is talking about.

So, bearing in mind that my two main systems are both Athlon XP 1700s, and that both have an X-15 Classic as their main drive, plus an older 7200 RPM SCSI drive as a spare, what benefit would I get from, say, grabbing a pair of shiny new IDE drives and RAIDing them?

If you have anything valuable on those boxes, RAID 1 would give you redundancy and therefore additional safety in case something goes wrong and fail inside one of your systems. From a performance viewpoint, the applications you use would probably not benefit much from any type of RAID IMO.

 

[Mercutio]

On IDE disks, there's no good reason to do performance-enhancing RAID0 (striping). This is the major application of IDE RAID, and to be honest, it's not terribly helpful for everyday sorts of things.

RAID1 represents an expectional value, if you have a system that can do it. 20GB drives are more than adequate for most people's desktop storage and are available at an appealing price point ($60 US). I've done RAID1 on client machines lots of times, usually software controlled. On a proper hardware controller, RAID1 offers nearly the performance enhancement of RAID0, since read requests can be serviced by both disks. There are no proper RAID controllers for IDE drives. At least none that I'm aware of.
RAID1 doesn't guard against user stupidity, which, in my experience is the major cause of data loss. If some data is truly critical, though, it's very good thing to have.

RAID5 is very much a "server" raid application. 3+ disks, data striped across all, plus some parity info in case you lose a disk (but you knew that). Most IDE controllers can't do this at all, and most reasonably-priced SCSI controllers can't do it very well - at least not with superfast, modern SCSI disks. This one actually works better from software. You aren't using all the power of the 2GHz CPU in your server, anyway. Windows NT and most Unix-like systems are perfectly happy to use your system CPU to run a RAID5 array. Linux can even bot off a software RAID5.

RAID 10 is a mirrored stripe set. You need four disks, so it's not cheap, but it's still a delicate situation, since losing disk1 from both mirror sets still kills your array. RAID10s are very, very fast, and IDE and SCSI RAID controllers do these just fine.

JBOD is "Just a Bunch of Disks". There aren't many good reasons to do JBOD, but you could make your PC see your 3 160GB disks as one 480GB space, which is probably useful at least sometimes.

To recap: Mirroring is useful for everyday sorts of things, for some people. Other than that, you can be blissfully ignorant.

 

[Handruin]

I have material to do an article on raid. It will take some time, but I was thinking about adding it to this site. This doesn't help out much here, but give me some time and I'll throw something together.

 

[CougTek]

RAID 10 is a mirrored stripe set. You need four disks, so it's not cheap, but it's still a delicate situation, since losing disk1 from both mirror sets still kills your array

You might lose the array, but if a single drive fails, you don't lose any data.

Let's say you have four drives : A, B, C & D. Drive A&B are striped together and C&D also. AB is mirrored with CD. If any of those drives fails, you won't lose any data. The array will die, but you'll be able to find the same data on the other mirror so the bottom line is that you only lose time. You'll only lose data if one drive of each mirror fails, pretty rare in my book.

RAID 10 is the best of both world IMHO, but you gotta be able to afford it.

 

[Mercutio]

Let's face it: Lose two drives in any redundant RAID, and you've lost data or had to deal with a major service interruption. Personally, I'm happy with the recovery options and greater available with RAID5 on big-dollar hardware, or just sticking with RAID0 mirroring. RAID10 isn't something you're going to deploy in a home user's desktop machine.

 

[Mercutio]

Replace "RAID0 mirroring" with "RAID1 mirroring".
That fulfills my idiot quotient for the day.

 

[Tea]

RAID10 isn't something you're going to deploy in a home user's desktop machine.

Really? Oh goodie! Can I have several of them please? I like things that are inappropriate.

Excuse me, gotta rush. Have to go polish the afterburner on my tricycle.

 

[Handruin]

Raid 10 is better suited for larger block I/O's IMHO as it would take a few ms to align all those heads for a seek. RAID 3 can offer spindle synch to achieve High write rates, but low protection. RAID 5 has a high overhead if you have a failed drive. It needs to calculate the XOR or something like that as it recreates the data from parity. Granted, degraded performance is better than data loss and no performance.

IMHO RAID1 is a good alternative with the cheaper price of EIDE these days!

 

[Santilli]

A raid fanatics view

Ok:
You don't really need it, your clients don't really need it, but, if you want it to happen right now, raid three more
X 15's on a decent dual channel card, and call me back.

It's really amazing the difference a 80-110 mb/sec disk system can make on your system.

If you really want to fly, use that same system on a 64 bit, 33 mhz bus, and proper card.

I find that with the faster processors, the mega ram we now have, that the impact of the hard drives is minimized, so, to really notice a big difference, you have to use multiple drives, in raid 0.

Computers are supposed to save time, and, raid saves lots of time.

IDE raid is still expensive for a decent card, and God know which drives work with which cards. Somethings haven't changed.

Is the time savings worth the money? I think so.

If you don't, in your position, you can sell off the extra drives, and the card, to a customer, cheap.

For backup, raid 1 in 2000 is a cheap way, with two ide drives, to make sure you don't loose valuable data.

gs

 

[Santilli]

Raid 10

Mirrored stripped sets are great for non-mission critical
operations, where down time is ok.

Unless you have some sort of power spike that kills more then one drive, you should be fine.

Mac guys I know swear by 10, and they do lots of raids.

Tannin, and Tea, I love your desire to use improper hardware.

go for it.

I have 4 x X 15's in raid 0 on a 1.4 gig Athlon system, using a dual channel ATTO card, and, it flys...

gs

 

[James]

The main advantage of running an IDE RAID0 setup for a while is that you are then extremely well qualified to tell people why they shouldn't ever use IDE RAID0.

 

[Tannin]

Excuse me taking so long to get back to this thread guys. It got kinda hectic there for a while. I can ramble on about weird old hard discs or foam at the mouth about the Microsoft monopoly or AMD's thermal non-protection without troubling to switch the brain cells into circut, but for this stuff I have to actually think.

Let me ask it another way. Let's say I don't care about data security - maybe it's my home machine - and I just want to go fast. Sitting there at the desktop starting ordinary desktop apps, at what point would the seat of the pants factor tell me that RAID 0 is starting to kick some serious arse? Or, put it another way, let's say I take two 5400 RPM drives, WD400AAs say, and RAID 0 them together. From the point of view of subjective performance, what single drive would they equal?


PS: Santilli! Whoah there! 4 X15s? I have a family to provide for!

 

[Tea]

I just read that again. Are you serious Greg? 4 x X15? Hoolie Doolie, that makes your rig to computing as SuperCaff's little Beamer is to cars. I'm jealous.

 

[Mercutio]

Well, things don't really work that way. Your 5400rpm drives, assuming they were of a type that works well in RAID0, would probably have a roughly 2x transfer rate. However, there aren't very many things an ordinary user does that are terribly transfer intensive. For 95% of what a typical desktop user does (Office apps, Browsing, Gaming), there's going to be absolutely no difference between RAID and non-RAID. RAID0 doesn't impact access time, which in my mind is the drastically more important characteristic in disk performance.

Desktop users looking for "faster" disk performance than what a modern IDE drive can offer would be better served to look at a single-drive SCSI solution like an Atlas 10k III or X15.

Which is probably what you wanted someone to say al along.

 

[James]

Let me ask it another way. Let's say I don't care about data security - maybe it's my home machine - and I just want to go fast. Sitting there at the desktop starting ordinary desktop apps, at what point would the seat of the pants factor tell me that RAID 0 is starting to kick some serious arse?

Never, unless you took up serious video or audio editing.

Or, put it another way, let's say I take two 5400 RPM drives, WD400AAs say, and RAID 0 them together. From the point of view of subjective performance, what single drive would they equal?

In most cases, it would feel like a bigger WD400AA. I even tried out a pair of WD272AAs on a 3ware card a couple of hours ago to refresh my (prejudicial) memory.

 

[Santilli]

I know it SHOULD work, but, how much money do you have to...

"The main advantage of running an IDE RAID0 setup for a while is that you are then extremely well qualified to tell people why they shouldn't ever use IDE RAID0."

I resemble the above remark;-)

Cheap ide raid cards pretty much, suck. Check me if I'm wrong, but good raid cards usually have additional memory, an additional processor, etc.

They just work better in raid.

Now, despite all the incompatibility problems, trying to determine what drives work with what cards, I KNOW, that one day, we will have a raid card that works, like the 3 ware, and makes ide raid worth doing.

Anyone get there?

That said, I just don't think you can beat a fast scsi drive, for boot, and tons of ram, with a fast processor.

Plus, thanks to MSFT, drivers for certain raid cards just aren't there. Buy a 700 dollar ATTO card, and never get a decent driver for 98, or XP. It works for 2000, and Mac os 9 back, but not 10.

So, my point being, raid cards are expensive, limited upgradeable items, that I would perfer, after this experience, not to buy another of.

Besides, the new X 15 is so fast, it takes a very serious raid setup to exceed it's data transfer rates, and it's seeks are unmatched. Davin and the boys would whine that it's not optimized for desktop use, but, it does have a 8 mb buffer, and the alogorithims can't be THAT funky. Isn't seek something like 3.2 ms?

By the way, yes, I did buy a bunch of 2nd generation cheetah X 15s, and, the only way to get a real bump was to put them together, though that wasn't the original intent.
They maxed out the mac at 75 MB/sec, and in the pc they do about 110 mb/sec, limited by sucky VIA chipsets, on a AMD 760 based, Asus 266 board.

Still, they move.


However, given the increase in processor speed, and the amount of ram most systems have, currently, it takes a really huge jump in speed to make the raid worth doing.


If you have the parts laying around, do it, but, a single X 15 is just fine, and, the excessive, absurd prices of raid cards doesn't justify the cost, in my opinion, over a single, new X 15.

Did I mention the 'advanced' quality of most raid cards bios software? Can we say, sucks beyond belief???

I've heard IBM raid bios the worst, Atto ain't all that good, and, Adaptec is ok.

Gary swears by the cards that are now made by LSI. See how that works out.
"So, bearing in mind that my two main systems are both Athlon XP 1700s, and that both have an X-15 Classic as their main drive, plus an older 7200 RPM SCSI drive as a spare, what benefit would I get from, say, grabbing a pair of shiny new IDE drives and RAIDing them?"

Damn Greg, read the question...

What are you doing? You already have scsi, why use a poor interface, in comparision, to raid slower drives, on a questionable card, when you boot off scsi anyway?

Happiness is an ide free machine...

If you want to go fast, buy another X 15, a new one, and use the old ones for pagefiles...and storage.

Or use 2k's raid software, to create a raid 0, using another 7200 rpm scsi drive, that matches yours exactly.

As we discussed in the past, scsi, even with old drives, can be, and usually is, far superior to any ide setup.

gs

Hope this helps...

 

[Santilli]

Don't invest in something you won't be able to move to the..

new motherboards with. I'm stuck with a 33 mhz/32 bit pci bus, period. That's what my card works with, despite advertizing to the contrary.

This kind of means, that barring major problems, I'll use this system for 10 years to get my money out of it, and, I won't be able to transfer the raid to a new motherboard, since they will have different pci slots, and, chances are good, atto will not have drivers for a new os.

gs

 

[Santilli]

Tannin: no resale value. Due to financial problems, mainly

due to MSFT, and their f....g management, my stock investments, using mom's money, that had in the past, provided income, are now gone.

The second gen X 15's, and the current climate around here for server parts, made the drives worthless.

2k=0. Not an investment I would suggest, unless you can resell the drives.

Is it worth it? It does happen NOW...

gs

 

[Bozo]

I see Tekram has a new IDE RAID card out. Has anyone heard anything about it? http://www.tekram.com/

I have a 3Ware 6200 with 2 75GXPs running RAID 0. (Living on the edge of disaster :mrgrn: ). Its been running for two years or so without problems. I use Drive Image to back it up on a regular basis. The operating system is on a separate hard drive (another 75GXP... :eekers: ).
As I do some beta testing, I loaded all my application and program CDs to the RAID array. Installing those programs is extreamly fast. Saves a lot of time.
The boot drive is removable. This way I can install another hard drive and a different operating system and load the programs from the array. No switching CDs.
I have installed programs to the RAID array but have found they don't run any faster than being on the boot drive. Maybe they load faster, but its hard to tell.
For some reason, burning music CDs from the RAID array give a lot of pops and clicks (dropouts???) in the finished product. I don't have this problem when burning from the boot drive. Never have come up with a reason for this though.

I wouldn't recommend Win2k software RAID for one reason. It can't be backed up with Ghost or Drive Image and some disk utilities won't work on the Dynamic disk either.

I set up an IBM Netfinity Server in RAID 10 using four 15000 RPM SCSI drives. Performance sucks donkey balls. IBM tech support reply was...'duh' (insert picture of knuckle head picking his nose.)

What this all boils down to is that RAID for the average user is not very practical, and you might not get what you expected even after spending tons of money.

But it is a great learning experiance.

Bozo

 

[Bozo]

One other thing................

IMHO, don't use a Promise IDE RAID card, even if it's free. Been there, done that, learned the hard way

Bozo

 

[Tea]

Quick! Tell Santilli!

 

[Santilli]

rofl: right Tea

rofl, very funny... :lol: [/i]