RAID Array Recovery from failed controller

[jen4950]

Here's a relatively simple question.

Say I've got an Adaptec 51645 SAS RAID card with 6 256GB SSD's in RAID 10 (OS) and 6 2TB WD RE4 drives in RAID5 (Data).

With those two arrays, what happens if the controller card drops dead? Is the configuration info stored on the card, or is it stored on the drives in the array?

Can I plug a new card in and drive on?

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I've already got a PERC 6/i card installed and running well with a couple 15k SAS drives - (new Dell Precision T7500) I'm working on taking it to the next level while maintaining a reasonable level of redundancy and data security.

[EDIT]

I've already got my Xeon X5680 Precision T7500 machine with a Quardo FX4800 and 30" Dell . And I've ordered 6 2TB WD RE4 drives, an Adaptec 51645 and the BBU. I haven't ordered the SSD's yet. The real fundamental questions are 7 2TB drives in RAID6 or 6 in RAID5 for 10TB, what is the level of recoverability from a controller failure, and is there a performance advantage of running 1 array from the 6/i and one from the 51645, or is the advantage with running both arrays from the 51645?

 

[Drudenhaus]

RAID metadata is usually stored at the end of each drive in the array (if it were stored on the card, you'd lose it when the system is unplugged unless you had a BBU ). You shouldn't have any issues swapping in a new card of the same model. I've done this probably 100 times at work with different 3ware, Adaptec, and LSI controllers (though LSI likes to complain).

I think you'll only benefit from split controllers if you're bottlenecked by a single card. I wouldn't worry about the Adaptec card becoming a bottleneck unless you're pushing 1-1.2GB/sec throughput. I'd go with a single controller unless you have a compelling reason to use both that you haven't mentioned.

 

[jen4950]

That's what I'm leaning toward. I've also got a use for the 6/i and (2) 300GB 15k drives that I bought with the T7500, so no waste.

Conceptually it seems having two arrays on a strong enough card would be advantageous seem as though it doesn't have to travel across the bus for intra v-drive transactions, only interations with the other systems like CPU and Memory.

The only real concern I have is when the card dies, and you have everything running off of it.

 

[Drudenhaus]

The only realy concern is when the card dies, and you have everything running off of it.

On the other hand, having more critical components in a system results in a, theoretically, less reliable system due to there being more points of failure. Besides, overnight shipping exists for a reason

 

[jen4950]

On the other hand, having more critical components in a system results in a, theoretically, less reliable system due to there being more points of failure. Besides, overnight shipping exists for a reason

Yes- you've got it.

So can you build a system without multi-system redundancies (Cluster / High Availability systems) that has a high failure recoverability rate on the cheap?

I'm not running Amazon or EBay. But I want high performance and high recoverability. High availability is third on the list- so If it's high performance yet craps out, I want to be able to plug a commodity part in and recover the system- even if I'm down for a bit; even a day or three..

 

[Drudenhaus]

Yes- you've got it.

So can you build a system without multi-system redundancies (Cluster / High Availability systems) that has a high failure recoverability rate on the cheap?

I'm not running Amazon or EBay. But I want high performance and high recoverability. High availability is third on the list- so If it's high performance yet craps out, I want to be able to plug a commodity part in and recover the system- even if I'm down for a bit; even a day or three..

There is still one more step you can do for high availability/recoverability of an array:

With a dual expander backplane (i.e. Supermicro 826E2/836E2/846E2), you can have multiple controllers setup for failover, effectively giving you a RAID1 of RAID cards. That would definitely not be "on the cheap" though and you would introduce another point of failure (the backplane).

Else, have a spare parts kit for an on-site repair (not really any cheaper though).

Aside from the array, unfortunately, there isn't terribly much you can do to provide redundancy for core components like the motherboard, CPUs, memory without having another system.

 

[jen4950]

RAID metadata is usually stored at the end of each drive in the array (if it were stored on the card, you'd lose it when the system is unplugged unless you had a BBU ). You shouldn't have any issues swapping in a new card of the same model. I've done this probably 100 times at work with different 3ware, Adaptec, and LSI controllers (though LSI likes to complain).

I think you'll only benefit from split controllers if you're bottlenecked by a single card. I wouldn't worry about the Adaptec card becoming a bottleneck unless you're pushing 1-1.2GB/sec throughput. I'd go with a single controller unless you have a compelling reason to use both that you haven't mentioned.

Six RE4 2TB Drives will have a combined theoretical sustained thoroughput of about 830 MB/s

Six OCZ SSD's will have a combined theoretical sustained thoroughput of about 1710 MB/s

An 8x PCIe bus is theoretically 2000 MB/s

Each array independently will be around the upper limit depending upon the RAID configuration. So if I am transferring from one drive to another and both arrays are on the same controller, does it go thru the bus, or does the traffic stay inside the RAID card?

 

[FireWire2]

Speed is seem to be the feature you are after!

Your T7500 has PCE express V2.0 which is 5Gb per lane... May as well look at the raid card feature PCI express 2.0

 

[jay2472000]

Nice system. Just out of curiousity what are you doing on the machine? I couldnt imagine ever needing almsot a gig of redundant SSD and another 10 Tb worth of raid in the same machine so I am curious.

 

[jen4950]

Nice system. Just out of curiousity what are you doing on the machine? I couldnt imagine ever needing almsot a gig of redundant SSD and another 10 Tb worth of raid in the same machine so I am curious.

I work a lot with CS4 Master Collection (getting ready to upgrade to CS5), and am tinkering with video production a little bit. I've gotten really into photography; I'm using a Canon 5D Mark II right now. Stiching together very high resolution panoramas and HDR stuff is a lot more fun to do with a lot of horsepower.

I'm also a structural engineer by training (not practicing or licensed), and like to work with AutoCAD. I'm going to start working on a new house design pretty soon, so I'll also be doing some architectural rendering and working a lot in 3D.

Finally, I'm combining a lot of older machines into one- so its going to be my media server, workstation, and file server. I've got about 2.5TB of pictures alone across several machines right now; and that doesn't include music and hundreds of our CDs that haven't been added to the library yet. I'm also slowly but surely convincing my wife that PC's are better than Macs- so I've got to get this one right so I don't get an I told you so when it doesn't load iTunes in microseconds. It's worked so far- I got her a new multicore Dell laptop with 8GB of RAM and 7 64bit, and she loves it compared to her 7 year old iMac (go figure!).

But mainly, I'm sick of jacking around with broken, unreliable machines- most of which I've built. So I'm going to try out a high end pre-built machine with matched and tested components and see if I have better luck and a better experience this time around. I build out a high end machine every 5 or 6 years that gets me to the next technology wave, and then I'll do it again.

 

[jen4950]

Speed is seem to be the feature you are after!

Your T7500 has PCE express V2.0 which is 5Gb per lane... May as well look at the raid card feature PCI express 2.0

So if I'm looking for a PCIe v2.0 8x RAID card that has the ability to host 2 x 6 drive internal arrays (one RAID 10 SSD array and one RAID 5 HDD array) and has external SAS connectors for an enclosure, and doesn't need an expander card- which ones fit the bill?

I convinced myself a couple days ago that the Adaptec 52445 was a good choice. And then I remembered all the trouble I had with an Adaptec card a couple years ago- so I'm not completely sold on it. Looking for recommendations.

 

[jen4950]

Any more recommendations?