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#1 2007-02-28 11:00 am
- Kendall
- Member
- From: Saskatoon, SK, Canada
- Registered: 1999-03-25
- Posts: 1118
RAID Formatting
Hi. I bought an Nspire NSP-E350B4U USB RAID enclosure yesterday. Basically, it takes four IDE drives (which I already had) and makes them either one big drive, two drives or four separate drives. Unfortunately, it's only USB 2, not Firewire, but the price was good.
Does anyone know, in theory whether I would get better speeds by makes one big drive out of the four or having four drives and striping them with OS X. I know if the drives were each on their own bus then the stripe would be better, but what about when they are all on the same bus?
What I want to use this for is a giant iTunes library with all of my DVDs on it. :-)
Thanks.
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#2 2007-02-28 11:08 am
- mahakali
- anti-razor
- From: easter egg
- Registered: 2002-11-06
- Posts: 5584
Re: RAID Formatting
Probably not but you can up the block size if you use it for large files. However, will it make any difference considering USB2 can't transfer faster than 480MB/s (even less, in practice)?
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#3 2007-02-28 11:48 am
Re: RAID Formatting
in theory, having the usb enclosure make the 4 drives show as one will be faster then striping them in OSX because OSX only has to manage one drive and not bother with RAID, the enclosure will do it for you meaning that reads and writes will use less CPU then if OSX had done the striping (and possibly less overhead on the USB bus)
realistically however you won't be able to tell the difference, the RAID will be so much faster then the USB bus that your speed will be completely bound by the speed of the USB bus
i would probably go with the software method and do the striping in OS X, it will be more configurable and that might make a bigger difference, increasing the stripe size and block size can give a decent boost in speed depending on what type of data your dealing with
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#4 2007-02-28 3:37 pm
- Kendall
- Member
- From: Saskatoon, SK, Canada
- Registered: 1999-03-25
- Posts: 1118
Re: RAID Formatting
I will be leaving work in about half an hour. I will give both a try and let you know how it turns out.
I'm pretty excited about having 1TB of external storage. hehe
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#6 2007-02-28 9:32 pm
- sturner
- Royal High Poobah
- Moderator
- From: Carrollton, TX USA
- Registered: 2000-01-31
- Posts: 13795
Re: RAID Formatting
With four drives of equal sizes the best configuration is stripping in pairs and mirroring the pairs.
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#7 2007-02-28 10:18 pm
- Kendall
- Member
- From: Saskatoon, SK, Canada
- Registered: 1999-03-25
- Posts: 1118
Re: RAID Formatting
Well, the striping didn't even work. It locked up every time I tried to write to it. Oh, well. No big deal. I would do the striping and mirroring thing but I really want the 1 TB.
So I stayed with the ONE BIG DRIVE. And I named it "TerrorByte." Okay, not all that clever, but what can I say?
Since the drive will essentially only hold a gigantic iTunes library for use with an AppleTV, everything will be backed up elsewhere. So it doesn't matter all that much if a drive goes down. Okay, I don't want one to go down, but you know what I mean.
Does anyone know what kind of speeds are good? I copied 7.74 GB to my TerrorByte and it took just over 8 minutes. Is that good or bad? Remember, it's USB, not firewire.
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#8 2007-03-01 3:06 am
- rufio
- Let the funeral start, hear the casket close...
- From: texas/ohio
- Registered: 2003-10-26
- Posts: 2261
Re: RAID Formatting
Kendall wrote:
Well, the striping didn't even work. It locked up every time I tried to write to it. Oh, well. No big deal. I would do the striping and mirroring thing but I really want the 1 TB.
For some reason this doesn't surprise me at all out of USB 2.0. It still sucks, I'm just sayin...
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everything is second after first."
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#9 2007-03-01 9:05 am
- Kendall
- Member
- From: Saskatoon, SK, Canada
- Registered: 1999-03-25
- Posts: 1118
Re: RAID Formatting
rufio wrote:
Kendall wrote:
Well, the striping didn't even work. It locked up every time I tried to write to it. Oh, well. No big deal. I would do the striping and mirroring thing but I really want the 1 TB.
For some reason this doesn't surprise me at all out of USB 2.0. It still sucks, I'm just sayin...
Yeah, it does suck. But the drive is still pretty sweet! And I won't need super duper speeds or anything.
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#10 2007-03-02 10:49 pm
- ElectricSheep
- Member
- Registered: 2003-07-20
- Posts: 109
Re: RAID Formatting
You would have also had to consider the fact that if you did go ahead and stripe all of the disks together, you would have increased the probability of total drive failure by nearly 400%. If one drive goes in a striped array, you lose everything.
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#12 2007-03-03 11:08 am
- ElectricSheep
- Member
- Registered: 2003-07-20
- Posts: 109
Re: RAID Formatting
Slip of the fingers. I could just as easily say that you are four times more likely to suffer a failure that results in a loss of all data.
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#14 2007-03-03 11:19 am
Re: RAID Formatting
Anyway. If it's just the convenience of having all four disks in one volume, you may be better of with a JBOD array. I think OS X supports that. The chances of drive failure are still high, but you won't lose all your data.
,xtG
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#15 2007-03-03 12:44 pm
- Kendall
- Member
- From: Saskatoon, SK, Canada
- Registered: 1999-03-25
- Posts: 1118
Re: RAID Formatting
Well, the drive enclosure I bought will make all four drives into one, so that's what I'm going to use. And, like I said, I will have everything on DVDs anyway, so a failure won't be the end of the world.
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#16 2007-03-05 12:46 am
- ElectricSheep
- Member
- Registered: 2003-07-20
- Posts: 109
Re: RAID Formatting
Alien wrote:
You mean to say striping four disks increases your chances of data loss due to drive failure fourfold?
You don't say…
,xtG
.tsooJ
Of course, that assumes you are using drives that have very, very small rates of failure. If you had drives with a quoted failure rate of 6% after one year, the risk factor of striping four together only goes up by a factor of about 3.5. If you striped seven of those drives together, the risk faster goes up by a factor of less than 6.
If you want to be picky about it...
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