Scsi Raid config question

cavemanoc

cavemanoc

cavemanoc

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I'm about to reformat and start again (again, again, again...) And was thinking about the way I've got my arrays set up. I'm using the Perc 4e/DC / Lsi Megaraid 320 2e which has 2 channels, 15 'drives' each.

I'll be setting up a 3 Disc array, a 4 disk array, and a 2 Disk array (all Raid 0). I'll be setting up on 64kb, writeback, adaptive read. Any changes to those?

Big question: for the 4 Disk array: (4xSeagate 72 Gb 15k4 drives) would it be faster with all 4 on one channel or 2 one each?

Also - I've got 2xSeagate 72Gb 15k3 drives - would it be best to raid them alone, or add them to the 4 disk array above?

Cheers
 
At a guess I'd split the 4 disk array across the channels - there's a 320Mb/s limit on each cable and 4 x 15k4 could get close to that.

I'd keep the 15K3s separate too, a 6 disk RAID0 array is a bit big for my liking and having mismatched drives isn't going to give you optimal performance.
 
Thanks for that - I was hoping this thread would catch your eye :D

Since I've lost windows I might do a bit of benching and spend some time trying different options to see what gives the best performance. I double checked the drives and the 2 'other' are definitely 15k3's so I'll keep them seperate. So far I have to say I haven't been blown away by this controller - it's fast (150mb/s ish) but certainly nowhere near the magic 320 - hopefully the 4 disks will start to get closer (theoretical max read of 80Mb/s per drive... :D ) But reading around I'm yet to find anyone with more that about 160ish... seems odd.

If I can't get past the 200 mark I think I'll just chuck the whole lot and see if I can get one of those nice Adaptec cards and some of those new Seagate sata's ;)

I saw in the HDD benchmark thread that you got some awesome scores out of yours (even with raid 5 :eek: ) but that was with 8 drives - what kind of performance you you expect with a Raid 0 of 4x7200.10's?
 
cavemanoc said:
I saw in the HDD benchmark thread that you got some awesome scores out of yours (even with raid 5 :eek: ) but that was with 8 drives - what kind of performance you you expect with a Raid 0 of 4x7200.10's?
Click to expand...
Yeah, but it's 8 x T7K250s, it feels like the case is going to shake itself apart when it's reading heavily ;)

I've got a pair of 7200.10s in RAID0 which aren't perfect (and I can't be ****ed messing about with them any more) but I still get 115Mb/s average. I have a feeling that there are some 4 disk RAID0 benches in the benchmark thread.
 
matja said:
on a 15k drive? I'd be surprised if it went that slow...
Click to expand...

From the Seagate site:
  • 15k4: Up to 96-MB/s sustained transfer rate
  • 15k5: Up to 125-MB/s sustained transfer rate

The older 15k3's were 70-80ish, bearing in mind that's an 'up to' number - you'd be lucky... ;)

I'd be very happy if I got 80 out of my 15k4's (in fact that's about what I got when I benched one on it's own!)

Anyway - just rebuilding the rig now - will split the arrays across the 2 channels and see what it can do!
 
Well - this is turning into a complete goat! I've got the system back up and running any everything is behaving nicely:

c: 3x18Gb 15k.3 in Raid 5 - Windows
d: 4x72Gb 15k.4 in Raid 0 - Speedy drive
e: 1x36Gb 15k.4 in Raid 0 - Programmes...

(Had to mothball the 2x72Gb 15k.3's as I'm out of connectors :rolleyes: )

Ran the Benchies:
c: 120mb/s - about right I would have though
e: 79mb/s - again - about what I expected

d: 130mb/s - :mad: Not happy at all - this is all turning into a farce (especially as my 3x18Gb's in Raid 0 were giving me 150mb/s +)

I've tried all the obvious things and am working some of the more obscure features. I was a little intrigued by one of the windows options to set the minimum 'data size' on partitioning - thought that might help if it matched the stripe size - but it didn't.

Any ideas what the problem could be - these should be nearly twice that speed?!?!
 
Hmmm... I've changed the stripe size to 128kb and the scores have jumped back to the 150mb/s mark - odd as I always thought smaller stripes gave faster bench results - Still not very impressed - was getting that out of a couple of 15k.3's so this should be considerably faster - the peak speed it topping out at around 200mb/s so there is definitely hope - the graph is completely flat (ie. no tail off towards the end of the drives) so it's not the drives but the adapter/bus that's the bottleneck - just can't seem to find a way around it - should be capable of much faster speeds - I'll post up a coupld of HDTach shots a bit later. Any ideas welcome :confused:
 
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