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8 drive external array--Your ideas?

post #1 of 7
Thread Starter 
Hey guys,

I'm working on the plans for a raid array. The array will be in an external case and be connected to my PC via a 9 foot long SAS cable going to a RocketRaid 2322.

The whole setup will look like this:

RocketRAID 2322(raid controller) -> 3-6 meter [SFF-8088 to (4)7 pin SATA] -> External case (8 2tb Western Digital Caviar Black )

My questions:
1. Will the RR2322 be able to support a connection of 1GB/s?

On the specs, the RR2322 supports only a 3Gb/s connection. I assumed this was a 3Gb connection to the hard drive and not the total bandwidth of the SFF-8088 connection.

My main concern in this system is going to be speed. Therefore, this array will probably be RAID 0, or raid 6.
2. Will the drives that I have selected be alright for such an array((8) 2tb Western Digital Caviar Black )?

Ive heard that the non enterprise drives are bad for large arrays and will frequently drop out of the array.

3. Are the SFF-8088 to SATA cables reliable for such a data intensive array?

4. Will the length of a 3-6m SFF-8088 to SATA cable be an issue?

These cables have always seemed strange to me... why would addonics make a multilane connector for something like this if there are cables that natively support it?

Addonics bridge:
http://www.addonics.com/products/mul.../connector.asp

5. What are your other ideas for this?

Links to devices:
Controller card:
http://cgi.ebay.com/ws/eBayISAPI.dll...=STRK:MEWAX:IT

SAS to SATA cable (I emailed the guy, he said he could make me one the size I need):
http://cgi.ebay.com/iSAS-7P88-F-4-7-...item5ad283f788

External case:
http://cgi.ebay.com/ws/eBayISAPI.dll...=STRK:MEWAX:IT

http://cgi.ebay.com/ws/eBayISAPI.dll...=STRK:MEWAX:IT


Just to let all of you guys know, this is my first array. I know im kinda doing a lot for my first RAID system, but I think I can handle it.


Once again, thank all of you!
You guys continuously help me whenever I need support for stuff like this.

I am planning on building this around black friday, but i will gather things as they go on sale.
I would like to make the total of this array around 800.
Edited by OverShocked - 6/4/11 at 12:56am
i7
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i7
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post #2 of 7
First question - what's it for? You may well get much better performance from an SSD or 2 as scratch disks for your work plus a storage array to keep large files later, rather than try and build a super fast, super size array for everything.

A cheap mATX case plus reasonable PSU (CX430 or similar) may well be cheaper (and more compact) than that case - especially if you get one that will hold most of the drives in ready-made 3.5" mounts rather than going for bay converters for everything.

A file server may be an even better place to store your data - that way it's accessible from more than 1 machine. A basic Sempron 140, 1 or 2 GB RAM, low-end mobo with 6 SATA ports, cheap 2-port SATA card plus FreeNAS on a USB stick or CF card will easily max out gigabit ethernet for low cost - and as you wouldn't need to shell out for the RAID card it'll probably be cheaper overall too.

I wouldn't try and run SATA drives using a 3m cable, let alone 6m. Although decent shielded SAS cables can do 10m, that ain't what you're using, and I wouldn't expect decent performance over 1m (the max for SATA cables). Although your card will drive with eSATA/external SAS voltages your drives won't. And how do you expect to hook up your drives anyway? Just passing the cables through the back of the case and hooking directly up to the disks is a recipe for disaster, either just having the cables pull out or worse breaking the drive connectors off completely.
post #3 of 7
Thread Starter 
The system is for large file conversions and large file storage (media etc.). Which is the reason this needs to be on a lone system and not a server. Of course the PC is networked though.

Good point, i didn't consider the power output of the SATA data cable. But isnt the power for these SAS data cables from the controller?

Yes, I was going to run the cable right into the back of the case for the array. I would come up with some kind of adapter to secure it.

However, you got me thinking...how well does infiniband work for an array like this?
Maybe an external case with 2 of these (http://www.addonics.com/products/mul.../connector.asp) would be good?

Then that would go to a raid controller for infiniband.
http://www.highpoint-tech.com/PDF/RR..._Datasheet.pdf

What do you think?

Thanks for reply!
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post #4 of 7
Sounds exactly like SSD/SSD raid to do the conversion on, then shift to a media server would be a much better fit - building fast storage arrays is a waste of time and money really, and a lot of hassle. My recommendation would still be to have a drive or 2 in your main rig, do the conversions/processing, then shift to the server to store your media. Better performance, lower cost. Also better security and more usability - you can watch the files on any PC without needing your main high power rig on at all times, viruses or system rebuilds/upgrades don't take your media offline etc. Plus expandability is much easier - if you run out of space with your RAID card you're looking at either another expensive card, case, etc, or buying an expensive SAS expander. With a server you add in another cheap HBA and a few more drives and you're all set.

I actually did something similar - which is why I know which way is best to do it. I started with 8 250GB RE3s in RAID (SSDs were WAY too expensive to think of doing this with when I set up my system a good few years ago now) to do video & audio conversion & media storage. But it wasn't as fast as I would like (even with 8 spindles you're still limited by mechanical disk performance), and there is no easy way to upgrade it. So now I have a separate media server with my 2TB drives in. I still do all the processing on the RE3s, but the output files are transferred to the media server once the conversions are done.

The signal voltages are whats important - there is no power transferred along a SAS cable. But the SAS card will use SAS voltages (1600mV rather than 600mV), but the SATA drives will only output SATA voltages - this is fine over short internal cables, but going to long external cables and all the interference problems that may result means it just isn't going to work reliably. There is a reason why SATA is limited to 1m...

You could go for Infiniband-type (probably less confusing if you stick to the 'proper' name of SFF-8470) connectors, but the cables and connectors and very expensive. It would probably be cheaper to stick with SFF-8088 cables as they are usually cheaper but perform the same.
post #5 of 7
Thread Starter 
Hmm, interesting idea. The type of conversions i do involve lots of disk usage... Ive got a 2tb now and the conversions only use 20% of the cpu because of the disk speed limitations. When you were doing this stuff did you manually move all the data to the server? Seems like it would take forever even on a gigabit switch.

As far as performance goes with an array like this, i was expecting something like 800MB/s sustained. I dont worry about random access so mechanical seems fine to me.

In my shoes, if power was not a concern (parents Pay electric bill so main rig is on all the time anyway) what would you do?

Yeah... looking at it again, the cost of the system with SFF-8470 would increase dramatically.

As much as i would love to have it externally, it seems like i would save about $300 to make it internal.

Thanks for your help.
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i7
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post #6 of 7
Over a gigabit ethernet network with decent NICs and any switch that isn't crap you can hit 80MB/s easily. Which is roughly 5GB/minute, or 1 minute to transfer a full DVD, maybe 5-10 mins to transfer a BluRay, depending on your final conversions. Which ain't so long, as the transfers won't really affect anything else - just set them going and get on with whatever you want. Or better still automate it...

You won't get 800MB/s from your array, even if you go with RAID0. You'll likely end up with closer to 650MB/s, in RAID6 it will be more like 500MB/s. And 2 C300s plus a couple of F4EGs for storage can match that in RAID0 for a lot less money than 8 2TB Blacks will cost. Newer-gen drives will be even faster (although more expensive), but the actual speeds you'll get will be heavily dependent on the board you run them off too. It's also worth noting that unless your reads are purely sequential you won't get anything like those kind of speeds from the array when doing your processing either, and instead will get a fraction of that. SSDs are largely unaffected by this problem though, and their non-sequential read performance is much, much better.
post #7 of 7
I am running a similar setup... if you use that card and raid 5 or 6 your throughput is going to be somewhere in the 3-400 range if you are lucky. I can't find my spreadsheet from when I was using the ol' rocketraid, but it was pretty dismal. I changed it out.

I have 8x2tb WD Blacks running off an adaptec 5805. I attached all the benchmarking I did in an excel spreadsheet. As far as how much speed you can get out of the single SFF, you are in the 1.1GB/s range, which should be more than enough for the array you are planning.

Enjoy!
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