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RAID speed problems
I am running a Dual 2.0 G5 with a sonnet 8 port SATA card… have 2 x 4 striped RAID 0 arrays… I was running disk speeds of around 200mb/s for both read and write… now I am running around 90mb/s write, and 200mb/s read for one of my RAID arrays.
The drives are 4 x 300GB seagates totally empty, with a total volume of 1.9TB when mounted as a RAID. Yesterday, with Softraid, I initialized all of the drives as separate, single SATA drives. The drive speeds I got were the following –
1- 61 mb/s write, 64 mb/s read
2- 56 mb/s write, 56 mb/s read
3- 57 mb/s write, 58 mb/s read
4- 65 mb/s write, 66 mb/s readAre the 56 mb/s write and read speeds enough to slow the whole array down? Or is it my sonnet card? My other 4 drive array was getting around 200 mb/s for write & read last week, but now is only getting around 130mb/s…
I’m stuck… and would like to do an 8 bit HD online coming up…
Just wondering if anyone can help.
Morgster
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6 Replies
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The RAID will slow down to the slowest disk in the RAID, it’s just the way it works. Still even @ 56MBsec, that’s not enough to slow down the RAID that much. Your next test is to switch two of the cables of the slowest single drive and the fastest single drive to see if it’s a bad/slow port on the card. And why did you use softraid to mount single drives? Why don’t you initialize them in Disk Utility? Try striping the RAID set in OSX and not using SoftRAID and see if that helps as well.
Jeremy
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Jeremy,
Thanks for the response.
Tried mounting as a RAID 0 using Mac Disk Utility… got pretty much identical write & read numbers as using softraid…
Then I mounted them as single drives using Disk Utility… and switching a couple cables around as you suggested, but actually got the same numbers from the same drives again… in other words I swapped port 1 & 2 and the drive speeds stayed the same ( I got 65mb/s write and read on port 2 whereas I got 56mb/s before)… so I’m guessing it’s not the card?
Does it matter that when I RAID them together my write speeds are way down, but my read speeds are up over 200mb/s… what does that mean?
Where do I go from here?
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[morgster] “Where do I go from here?”
Good question. What I would do is RAID 3 of the disks together (leaving the slowest one out) and see if that makes a difference. If it does, break that stripe (yes again) and put the slowest disk back in and leave a faster one out (for another 3 drive raid set) and see what the speeds are then.
Jeremy
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Thanks for your help again…
Here are my results…
Striped channels 5/6/7 together – 110 write, 162 read
Striped channels 6/7/8 together – 74 write, 160 read
Striped channels 5/6/8 together – 43 write, 160 readStriped channels 5/6 together – 112 write, 114 read
Striped channels 6/7 together – 113 write, 116 read
Striped channels 7/8 together – 115 write, 116 read
Striped channels 5/8 together – 110 write, 109 readI thought that when I striped 5/6/7 together that told me that channel 8 had the bad drive on it… but when I only stripe 2 drives together, I get the numbers in the ballpark of where they should be.
So what now? I am totally stumped. Oh, and my other RAID array (4 drives) is posting speeds of over 220 mb/s constantly today… up from 140 yesterday… what the heck is going on?
Cheers.
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I am sorry morgster, this is confusing to me as well. I’d start by calling sonnet, and then you can try and track down Bob Zelin in the AJA io/Kona/or Blackmagic (and other) forums. He’s been there done that with all kinds of DIY raids.
Not having one place to call for support is tough.
Jeremy
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Yeah, this is a huge selling point for CalDigit and other fully assembled RAIDS. One company to call. I have a do-it-yourself Raid that I am semi-confident with. But if it fails, I’ll have a lot of troubleshooting to do.
Shane
Littlefrog Post
http://www.lfhd.net
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