: Benefiting off of a RAID Setup


monokitty
Nov 12th, 2004, 03:58 PM
Can someone please explain to me what the benefits are, if anything, to creating a RAID setup with dual 80 GB hard drives?

First setup: One is the main drive, the other is a backup drive - mirrored RAID - is this a good way of doing backups?

Second setup: Speed purposes-- so lost on this. How does this even work?

TroutMaskReplica
Nov 12th, 2004, 05:05 PM
don't do mirrored RAID - its stupid. any corruption on the primary drive will carry over to the second drive. it's better to schedule backups with psyncx.

the striped RAID (which i use) is what you want. basically your file is taken and split into pieces which are stored on both drives. when you open the file again all of those pieces are put back together kind of like a zipper, so you get (almost) double the throughput. any disk activity is almost twice as fast with a RAID set up. it also makes the OS faster since it is pretty much always doing something disk related.

the two (or more) drives that make up the RAID show up as one volume or HD in the Finder. on an older mac a RAID controller card should be used, since ATA33 and 66 don't have enough bandwidth to take advantage of the RAID.

TroutMaskReplica
Nov 12th, 2004, 05:07 PM
the big disadvantage of the striped RAID is stability. you are basically doubling the probability of hardware failure, which is why backup is even more important with a RAID setup.

Macaholic
Nov 12th, 2004, 05:11 PM
Coincidentally, I'm looking into a RAID setup for my old Sawtooth; the last piece of my upgrade puzzle graemlins/nuts.gif

You're right about the mirrored RAID. A redundant backup of files, written in realtime to both disks. To me -- and I could be wrong on this -- I think this generally kind of useless. A backup is crucial, yes, but I like the external Firewire route instead. You can detach the drive and leave it at your neighbour's in the possibility that your computer (or your house), FRIES!

The capacity of a redundant array is that (in your case) you will be left with 80GB of capacity (because the two drives have mirrored data)

The other RAID approach is a striped RAID. Here, the two drives appear as one drive to the system -- but a file gets segmented and those segments are written on both drives at the same time. The result is "twice" the speed (sorta). Plus with a striped array, you get the full capacity of BOTH drives, because the files are not being written redundantly across them. There's a big downside to a striped array, however, and that i that if one drive goes down -- ALL YOUR DATA IS LOST. So, you MUST backup your data, regularly.

I'm planning on installing a 360GB striped array with dual 180GB 7200rpm Hitachi drives with 8MB caches. ZOOM-frickin-ZOOM!!! http://deephousepage.com/smilies/driving.gif

Macaholic
Nov 12th, 2004, 05:13 PM
I take too long to compose a reply. I started before TroutMaskReplica posted :D

monokitty
Nov 12th, 2004, 05:23 PM
So basically, in a striped RAID, if one drive goes down (even though you have 2 physical drives), all your data goes down with it. So, that being said, I'd need 2 x 80 GB drives for the RAID, plus a 160 GB drive not in the RAID, as a backup drive, meaning I'd need 3 physical hard drives - plus an ATA/133 controller. :D

Wow, RAID solutions aren't cheap. :D

used to be jwoodget
Nov 12th, 2004, 05:29 PM
I striped a pair of internal SATA Hitachi 250 gig drives in my G5. There's a bug in the Apple disk utility that macdoc knows how to avoid but apart from that, its truly seamless and significantly faster than a non-Raid system - especially if you have SATA disks.

The 500 gig .Mac backup is kinda expensive though ;)

Macaholic
Nov 12th, 2004, 08:49 PM
, I'd need 2 x 80 GB drives for the RAID, plus a 160 GB drive not in the RAID, as a backup drive, meaning I'd need 3 physical hard drives - plus an ATA/133 controllerYou crunched the numbers properly graemlins/greedy.gif

TroutMaskReplica
Nov 12th, 2004, 09:06 PM
you could probably get by with a backup drive with a lower capacity, unless you need to have a bootable clone of your entire system. i prefer to start out fresh when something bad happens though. i have an 80 gig raid made of 2 WD 8 meg cache drives, then i use a 40 gb drive + an old 20 gig drive for backup.

i keep an os 9 system folder on the 20 gig because you can't have your os 9 folder and your RAID on the same volume - OS 9 won't recognize it.

Macaholic
Nov 13th, 2004, 11:12 AM
Now, here's a question: Will there be a noticable difference between doing a striped RAID on an ATA100 bus or an ATA133 bus? I plan on getting the Sonnet tempo 133 card, but I just thought I would ask.

m_gear
Nov 13th, 2004, 11:30 AM
Well, I think I can answer at least part of this question. I benchmarked my system when it was a single disk (http://ladd.dyndns.org/xbench/merge.xhtml?doc1=54602), then set it up as RAID 1 (http://ladd.dyndns.org/xbench/merge.xhtml?doc1=71698) and RAID 0 (http://ladd.dyndns.org/xbench/merge.xhtml?doc1=71691) and also recorded the xBench scores for those. Keep in mind these scores are for dual 7500 rpm SATA drives, so performance on faster (i.e. SCSI, SATA 1.5/3.0, more drives) or slower (PATA, FireWire) hardware may vary.

TroutMaskReplica
Nov 13th, 2004, 11:55 AM
macaholic, the ata 100 bus would be fully saturated with a RAID setup, so the ATA 133 is a necessity.

keep in mind not everyone needs a RAID. it makes a HUGE difference with Photoshop and large files, since there is a lot of swap disk activity as well as simply opening and saving a huge file takes half the time. however a 3d workstation, for example, can get by with the sh*ttiest 2mb cache drive, since it's all processor/GPU. i could be wrong but i don't think games hit the drives much either.

i don't know anything about the audio side of things, but i imagine you've looked into it and determined there is enough disk activity to warrant a RAID?

Macaholic
Nov 13th, 2004, 12:04 PM
If I read the results properly, it's interesting to see how the redundant array reduced speed over the single drive. For my particular scenario, these results don't really shed light on my query. I think I'll contact Rob Art at Barefeats and see what he says.

MacDoc
Nov 13th, 2004, 12:58 PM
You'll be fine with the 100 bus - the only meaningful number is sustained throughput for graphics video etc. No drive is fast on small random files.

You get about 90-95 megs per second sustained on the 100 bus versus 105-110 on the 133 bus. Not worth it in my mind.
Both are a big jump on the 48-55 of a single drive.

RAIDs MUST be both maintained and backed up and best if you use SMART equipped drives and run a SMART utility from time to time as it will predict possible failure.
My RAID is fully backed up automatically every three hours and the drives are server class Raptors.

Mirrored plus daily backup is also good strategy but not for the everyday user.
One client has 100 people accessing the database - a mirror is a must so he can continue working seamlessly til end of day.
:cool:

Good speed bump BUT backup is absolutely critical as is using good drives - 24/7 rated is a good idea. :cool:

TroutMaskReplica
Nov 13th, 2004, 01:08 PM
oops! i thought the choice you were giving was between the stock ATA (ATA 66, as it happens) and 133. my tired and beleaguered mind played a trick, telling me the ATA 100 you quoted was the stock ATA speed instead of ATA66.

needless to say, you'll need a card of some sort as the ATA 66 speed won't accommodate 100mb/sec transfer speeds.

MacDoc
Nov 13th, 2004, 01:31 PM
Ummmmm still tired perhaps - the MDD series have on board 100 ata buses - we put RAIDS in them all the time.

It's one of the "trade up" to MDD decisions having both the bays and the bus. :cool:

TroutMaskReplica
Nov 13th, 2004, 01:35 PM
i thought macaholic had a sawtooth? hence the ata 66?

MacDoc
Nov 13th, 2004, 01:41 PM
Yes but he's asking about a 100 ata bus - could be card could be internal bus. :cool:

used to be jwoodget
Nov 13th, 2004, 02:04 PM
Macdoc,

What back-up software do you recommend? I tend to do back-ups on a WIRAHTTT-DIM* schedule and it's probably not a good idea with my RAID drives..... graemlins/nuts.gif

Is Apple BackUp 2.02 sufficient (it can time back-ups to a disk)?


*When I Remember And Have The Time To Do It Manually. Pronounced "You Idiot!"

Macaholic
Nov 13th, 2004, 02:23 PM
My apologies, fellas. I ALWAYS confuse my 100MHz fsb with the ATA66 drive bus.

Yes, this would be a striped RAID for my Sawtooth. I am buying two 180GB 7200rpm 8Mb cache Hitachis from Macmaniac in Vancouver (pulled from xServes) @ $100.00 each. I currently have a 72 & 120GB 2MB cache'd drives internally. Will pull them and replace my 56GB external Firewire drive with the Seagate 120GB. That, along with my other 180Gb Firewire drive will be my backup.

I also intend to upgrade to Logic Pro v. 7, which FINALLY includes the first OS X compatible version of their Waveburner CD authoring program. Waveburner is the only reason I boot into 9, and I only do that maybe twice a year to update my demo audio CD.

Given that the Sawtooth is ATA66 (need I remind myself of this? YES! :mad: ) -- but my frontside bus is 100MHz, the real question is an ATA100 card (if they're still sold), or an ATA133 card.

Also, is a software RAID viable, given the economics of say, Sonnet's tempo ATA133 card, versus their more expensive RAID card. Again, maybe the 100MHz system bus may choke a hardware RAID...?...? :confused:

monokitty
Nov 13th, 2004, 04:20 PM
Whether or not to get an ATA/100 or ATA/133 card should depend on what standards your 180 GB drives are - if the drives have ATA/100 interfaces, then it won't do much to put them on an ATA/133 controller, will it now? ;) (they'll just run at ATA/100 standards.)

Or, you could just buy 2 x SATA hard drives and a Serial ATA controller. ;)

Macaholic
Nov 13th, 2004, 06:09 PM
Whether or not to get an ATA/100 or ATA/133 card should depend on what standards your 180 GB drives are - if the drives have ATA/100 interfaces, then it won't do much to put them on an ATA/133 controller, will it now?Thank-you for stating THE OBVIOUS. tongue.gif Plus, as I mentioned that the drives are:

A) 180GB
B) 7200rpm
C) 8Mb cache
D) pulled from xServes

They will NOT be simply ATA100. ;)

According to lowendmac (http://www.lowendmac.com/ppc/xserve-133.html), these drives propbably come from second generation G4 xServes... but I want to check on the amount of hours these drives have on them...

MacDoc
Nov 13th, 2004, 06:46 PM
You really don't understand much do you Lars tongue.gif
You ask about RAID then you talk as if you actually know something.

ATA 100 and ATA 133 are bus throughput maximums -NO SINGLE DRIVE ACHEIVES IT.

TWO ata 100 drives will still do 110 megs per second on an ata 133 card..

You just don't learn. :rolleyes:
Don't comment if you don't know........it's real simple.



Maca I'd not be concerned about hours - server drives are designed for 24/7 and time is really not a failure predictor since MTBF is measured in millions of hours on that class of drive.

Macaholic
Nov 13th, 2004, 07:01 PM
Thanks, MacDoc smile.gif

SkyHook
Nov 14th, 2004, 01:35 AM
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Macaholic
Nov 14th, 2004, 02:17 AM
Cool. My RAID will be internal -- and local.

TroutMaskReplica
Nov 14th, 2004, 08:49 AM
skyhook,

i didn't understand much of that, because of statements like this: "Databases tend to handle their own record checking, but imagine a home office where you have to courier something by the end of the day, every day. "

What does the first half of the sentence have to do with the second? i'm lost.

SkyHook
Nov 14th, 2004, 02:19 PM
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