SCSI RAID 5 with 3 drives on a 2-channel controller?

[MichaelD]

Hi guys,

I'm just feeding my brain on this one. I already have a SCSI Raid card. LSI Megaraid 1600 Elite. Dual channel card. Right now it's choked in a 32-bit slot...soon to be in a 64-bit, 133MHz PCI-X slot, though.

If I wanted to set up Raid-5 with three drives...wouldn't the performance of the array be affected as one channel would have two drives and the other channel only one drive?

Also, would 3-drive RAID 5 offer any better performance over 2-drive RAID 0? Thanks.

 

[Markfw]

Actually, the raid0 array might be faster. When I first tried raid5, it seemed slower. Also, are you sure you can put 2 drives on one channel, and one on the other ? The thing is, with raid5, you don;t have to worry about losing data if a drive dies. go 4 drives though.... Its hard to rebuild if those are your only drives. I have more than I know what to do with (not exactly) so copying the array over, and then changing it and copying back is not a problem.

 

[sharkeeper]

That HBA will work at 64/66 in your new board. Max bus speed = 512MB/S.

It is always better to stripe across channels instead of down channels. That said, with three disks performance will be much better with 2+1 instead of 3.

The three disk R5 will have the same performance as the R0 in your case since you will use WB caching. RAID5 writes will be much worse than RAID0 regardless of the cache settings. (in the long run--short writes of up to 80% of your cache size will be at cache speed)

NEVER use all three disks in R5 and boot off such an array. This is only a last minute resort and it will hurt performance dramatically.

In any case with a new system, the thing to do is get your OS up and running THEN ghost it. Then you can play around with different configs.

Cheers!

 

[MichaelD]

Thanks much, Shuttleteam and Mark.

Shuttleteam = The Godfather who "loaned me the money" to start my SCSI habit
mechBgon = The Pusher that give me the first taste...had to go to the Godfather after that!
Mark = The other guy that owes the Godfather money. <--my partner in crime

Reason I was asking is that I have a third 18GB Fujitsu MAS drive...right now it's in my server as the System drive. Was just thinking about it. Thanks!!! I'll leave my 2-drive stripe alone..for now. :evil:

Now...If I got another two drives...and did a 4-drive RAID-0 stripe. 4 x 15K rpm drives.... :shocked:

Heh, that's a pipe dream.

I do believe the new Opteron rig will be plenty fast enough, especially with the HBA freed from the chains of a 32-bit PCI bus. :shocked:

Thanks again, Shuttleteam.

 

[Markfw]

MichaelD+Shuttleteam+Mechbgon=Me spending way too much money !!

Next (since I have the motherboard and system to use it) will come this and the many drives it will make me buy !

 

[MichaelD]

:shocked: No...you're not gonna....

You are, aren't you? :evil: Daaaaaaaaamn...you will truly have the fastest rig on this board. And probably the most expensive, too.

I am very curious to see what kind of performance increase I'll see once I move my two-drive array over to a 64-bit, 66MHz slot. They ARE 15K drives...but on a U160 adapter.

I am GUESSING I should see about a 33% increase?

 

[Markfw]

Nope, its only 66 mhz also. First I want to see that happens to my array. Then I decide what to buy next.

Edit What I really need is this

 

[MichaelD]

Originally posted by: Markfw900
Nope, its only 66 mhz also. First I want to see that happens to my array. Then I decide what to buy next.

Edit What I really need is this

Ho-lee-crap. Can you say "$600 at Newegg?"

 

[Markfw]

Nope, they don;t have that on newegg. That the 66 mhz version. The x2 is the 133 mhz version. That ones $869

 

[sharkeeper]

This card is identical to the 320-2X. Out of the box, it will work flawlessly with a Crucial 512MB UNBUFFERED ECC DDR DIMM. The BBU is about $130 for this card and is highly recommended if you do anything important with your system!

The 400MHz X-scale CPU and PCI-X 133 will blow the doors off any other HBA you can use in your system. A bargain IMO. This coupled with four 15.3 disks and 128MB of cache or more (the standard product comes with 128) = 10k+ COSBI score. That's like a 45,000 3DMark03 score if it really matters.

You know the rest of the story...

Cheers!

 

[n0cmonkey]

lalalalalalalala! I can't hear you!

Come on guys, I can't spend money right now. My 2 U160 10k drives are feeling pretty wimpy right now, especially since the 3rd decided it didn't want to start up...

 

[Chaotic42]

Originally posted by: n0cmonkey
lalalalalalalala! I can't hear you!

Come on guys, I can't spend money right now. My 2 U160 10k drives are feeling pretty wimpy right now, especially since the 3rd decided it didn't want to start up...

No kidding!

Heck, I only have one SCSI drive. Well, I need to go to college, and I needed a new car. The SCSI is just for fun.

 

[n0cmonkey]

Originally posted by: Chaotic42

Originally posted by: n0cmonkey
lalalalalalalala! I can't hear you!

Come on guys, I can't spend money right now. My 2 U160 10k drives are feeling pretty wimpy right now, especially since the 3rd decided it didn't want to start up...

No kidding!

Heck, I only have one SCSI drive. Well, I need to go to college, and I needed a new car. The SCSI is just for fun.

So would now be a bad time to tell you I got a 9GB 10k rpm drive for free (along with one of the 3 controllers I have)?

 

[Chaotic42]

Originally posted by: n0cmonkey
So would now be a bad time to tell you I got a 9GB 10k rpm drive for free (along with one of the 3 controllers I have)?

Hang on, let me look at the clock...

Yes, it would be a bad time. Why, does that seem like something you're likely to tell me?

 

[n0cmonkey]

Originally posted by: Chaotic42

Originally posted by: n0cmonkey
So would now be a bad time to tell you I got a 9GB 10k rpm drive for free (along with one of the 3 controllers I have)?

Hang on, let me look at the clock...

Yes, it would be a bad time. Why, does that seem like something you're likely to tell me?

Nah, I'll keep that a secret. Did manage to get a free sun system (ultra 10/440) though. Couldn't get the cisco catalyst switch, but I'm not a big fan of cisco.

 

[mechBgon]

Hehe, you guys scare me

I have a 9GB 10k drive laying on its back on my living-room carpet at this very moment. It's enjoying the mechBgon Retirement Plan? but it may get pressed into duty occasionally as a holding tank.

 

[Chaotic42]

Originally posted by: mechBgon
Hehe, you guys scare me

I have a 9GB 10k drive laying on its back on my living-room carpet at this very moment. It's enjoying the mechBgon Retirement Plan? but it may get pressed into duty occasionally as a holding tank.

Well, I did get an 18.3GB 7.2K SCSI drive from my friend's dad a few years ago. I just need to find it, and I need an 80-pin converter. I'm too lazy/cheap to order one though.

 

[n0cmonkey]

Originally posted by: mechBgon
Hehe, you guys scare me

I bet the boxes full of extra parts at my house aren't quite as scary as yours.

I have a 9GB 10k drive laying on its back on my living-room carpet at this very moment. It's enjoying the mechBgon Retirement Plan? but it may get pressed into duty occasionally as a holding tank.

My free 9GB was the one that died. I'll have to get by with the 36 and the 18.

Next year. That's when I'll get a SCSI raid setup. Since the $290 lotto jackpot was won, and not by me. :|

 

[n0cmonkey]

Originally posted by: Chaotic42

Originally posted by: mechBgon
Hehe, you guys scare me

I have a 9GB 10k drive laying on its back on my living-room carpet at this very moment. It's enjoying the mechBgon Retirement Plan? but it may get pressed into duty occasionally as a holding tank.

Well, I did get an 18.3GB 7.2K SCSI drive from my friend's dad a few years ago. I just need to find it, and I need an 80-pin converter. I'm too lazy/cheap to order one though.

7200RPM? Bah!

I've got a few 50pin scsi drives around the house somewhere. And I think a couple of UW2 disks...

 

[Chaotic42]

Originally posted by: n0cmonkey
My free 9GB was the one that died. I'll have to get by with the 36 and the 18.

Next year. That's when I'll get a SCSI raid setup. Since the $290 lotto jackpot was won, and not by me. :|

If I win a big lotto jackpot, I'll buy you an 8 drive SCSI RAID setup when the new 22.5K drives come out. In fact, I'll buy one for all of the SCSI-freak crew here.

Of course, if you win, I expect the same.

 

[n0cmonkey]

Originally posted by: Chaotic42

Originally posted by: n0cmonkey
My free 9GB was the one that died. I'll have to get by with the 36 and the 18.

Next year. That's when I'll get a SCSI raid setup. Since the $290 lotto jackpot was won, and not by me. :|

If I win a big lotto jackpot, I'll buy you an 8 drive SCSI RAID setup when the new 22.5K drives come out. In fact, I'll buy one for all of the SCSI-freak crew here.

Of course, if you win, I expect the same.

Lotto's down to $10m. Not sure I can afford that. Too many comics to buy.

 

[mechBgon]

I bet the boxes full of extra parts at my house aren't quite as scary as yours.

LOL, well if you count my stash of bicycle parts... :evil:

 

[n0cmonkey]

Originally posted by: mechBgon

I bet the boxes full of extra parts at my house aren't quite as scary as yours.

LOL, well if you count my stash of bicycle parts... :evil:

If I let you count those, I get to throw in the candyland collectors tin I got for christmas!