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SATA Hard drives and RAID

S

spdntckt

macrumors newbie
Original poster
Jun 27, 2005
11
0
I was wondering if there is a FAQ floating around somewhere which talks about the mac OSX raid features?

I am doing some video editing of large files (some HD) - and am looking to add two more internal 400Gb SATA hard disks. From reading the documentation - it isnt clear weather or not the mirrored raid config will increase performance the same way that striped raid does? I know that mirrored raid is the best for automatic backup - but not optimal for capacity (which is OK) ->I rather like the auto-backup feautre of mirrored RAID, but need the extra performance as well. Do i have to use striped raid for that extra 'bump' in performance?

Also - what are folks recommending for SATA disks these days? i was looking at the hitachi 400g 7k400 drive. are those any good/reliable?

thanks for any advice!
 
Mirroring (RAID 1) never increases performance -- it is a security feature that gives you the same data on 2 drives. 2 x 400 Gb drives mirrored = 400 Gb, a bit slower because of the RAID processing overhead.

Striping (RAID 0) gives you faster speed for high volume use like video or servers -- at the cost of less security because a failure in any one drive takes out the entire data on both drives. 2 x 400 Gb drives = 800 Gb.

RAID 3, RAID 5, RAID 0+1 give a combination of mirroring and striping, using 3, 4 or more drive mechanisms. Expensive.

You don't have room inside a PowerMac G5 for two additional SATA drives. You are limited to the stock drive plus one more (there are third party brackets you can buy to add more mounting places for internal drives. I don't recommend them) Also there are only 2 SATA ports on the motherboard - 1 port = 1 drive.

I recommend you look at a SATA PCI-X controller and an external SATA chassis.
http://www.firmtek.com/seritek/seritek-1en2/
http://www.wiebetech.com/products/traydockesata.php

Consider the advantage of an external bay with removeable drives, so you can swap in fresh drives if you run out of room.
 
What about this?
I was thinking about buying one of those and using my old PCI-SATA controller to add a couple more hard drives to my G5.

Has anyone here used one of those brackets and know if they're a good alternative to external drives?
 
cwright said:
What about this?
I was thinking about buying one of those and using my old PCI-SATA controller to add a couple more hard drives to my G5.

Has anyone here used one of those brackets and know if they're a good alternative to external drives?
Click to expand...

I never heard of that one. I've been lookin into adding a few extra SATA drives, and I've found there are two main mods, both of which are over $200. I'm looking at getting this one, but I've also heard good things about this one. I was really concerned about heat issues, but the people who have gotten them haven't had any problems. They say it's only running a few degrees warmer. (F)
 
I've looked at both of those options too, but they appear to do the same thing as the G5 Drive Bracket and they're alot more expensive.

The G5 Drive Bracket is on sale for $75 shipped through the next week or so... seems like a much better deal.
 
cwright said:
I've looked at both of those options too, but they appear to do the same thing as the G5 Drive Bracket and they're alot more expensive.

The G5 Drive Bracket is on sale for $75 shipped through the next week or so... seems like a much better deal.
Click to expand...

Yeah, it looked pretty good. The only thing I would worry about is getting all the right cables and cards, but if you feel comfortable, then buy it. All the people who have gotten it have seemed to like it. If you have success or not, I would love to hear about it. I'm always open to saving a hundred bucks.
 
Thanks for the input.. is there a FAQ somewhere that explains all the differences between 0+, 2, 3?

I was planning to get one of the G5 brackets - like the ones posted earlier - to hold 4 total drives.. with an additional SATA controller card.. my mac has open slots
 
CanadaRAM said:
Mirroring (RAID 1) never increases performance -- it is a security feature that gives you the same data on 2 drives. 2 x 400 Gb drives mirrored = 400 Gb, a bit slower because of the RAID processing overhead.
Click to expand...

Isn't it true that RAID 1 increases read performance (perhaps only slightly) because there are twice as many places to find the same data, so the controller can split up the reads across the disks?

Thanks for the input.. is there a FAQ somewhere that explains all the differences between 0+, 2, 3?
Click to expand...

Google. Try 'raid faq' or 'raid levels'.
 
I know that some of this has been covered already, but here is my summery:

There are lots of different raid configurations, but these are the most popular:

RAID 0: minimum 2 disks, capacity = number of drives (ie 100%), no drive failure protection, almost doubles read and write speed
RAID 1: minimum 2 disks, capacity = half number of drives (ie 50%), can loose 1 drive per pair, almost standard write speed, faster read speed
RAID 10: minimum 4 disks, capacity = half number of drives (ie 50%), can loose 1 drive per pair, almost doubles write speed, more than double read speed
RAID 5: minimum 3 disks, capacity = number of drives less 1 (ie 3 drives = 66%, 4 drives = 75%, etc...), can lose 1 drive, slow write speed, faster read speed

A good hardware RAID controller is always recommended, especially for RAID 5 where parity data must be calculated for every write, otherwise your CPU will take a hit every time you read and write data.
 
Wonderful! Just when my hard drives were getting full and I was looking to buy another one, my 250GB drvie fails :(

Well I guess it hasnt yet, but Disk Utility shows that the S.M.A.R.T status is failing. The drive has always had a weird sort of whining noise (don't think I've even had it a year yet) and I never was able to get anyone at Hitachi to send me a new drive... couldn't find any warranty info on it. I bought it as OEM, not retail, but it should still have a warranty, right? :confused:

And I had a lot of work to get done this week on that hard drive :(
 
I have the G5 Drive Bracket which I purchased on eBay installed in a dual 1.8 Powermac. I have had no issues with heat at all. I have two 300GB Maxtor DiamondMax 10 drives in the bracket (and a total of four in the machine--250GB Maxtor boot drive and 74GB WD Raptor in factory slots). I run the two 300GB drives in a striped RAID array which I set up using Disk Utility. I run the extra drives from an Initio 1623 SATA host card plugged into the PCI-X slot. I puchased the Initio card because it is less than 1/2 the price of any other host card, but I would recommend spending the extra $ on one of the Firmtek cards as you can boot from these (not the Initio).

I use my RAID set up as a scratch disk for digital video editing. You should take a look on www.barefeats.com to research SATA drives. I chose the Maxtor's because they have better write speeds than other drives, but the Seagate SATA drives have an excellent warranty (5 years).
 
ShermDog said:
I have the G5 Drive Bracket which I purchased on eBay installed in a dual 1.8 Powermac. I have had no issues with heat at all. I have two 300GB Maxtor DiamondMax 10 drives in the bracket (and a total of four in the machine--250GB Maxtor boot drive and 74GB WD Raptor in factory slots). I run the two 300GB drives in a striped RAID array which I set up using Disk Utility. I run the extra drives from an Initio 1623 SATA host card plugged into the PCI-X slot. I puchased the Initio card because it is less than 1/2 the price of any other host card, but I would recommend spending the extra $ on one of the Firmtek cards as you can boot from these (not the Initio).

I use my RAID set up as a scratch disk for digital video editing. You should take a look on www.barefeats.com to research SATA drives. I chose the Maxtor's because they have better write speeds than other drives, but the Seagate SATA drives have an excellent warranty (5 years).
Click to expand...

Where did you get the cables and also which Firmtek card would I want?
 
Poeben said:
Isn't it true that RAID 1 increases read performance (perhaps only slightly) because there are twice as many places to find the same data, so the controller can split up the reads across the disks?
Click to expand...
LOTS of background:

http://www.storagereview.com/guide2000/ref/hdd/perf/raid/index.html

It boils down to how intelligent the RAID controller is. If it is a server-level hardware RAID controller with its own CPU and RAM that can queue read requests between drives, AND the traffic volume is high, potentially you get faster reads on a RAID 1.

However, sofware RAID requires CPU time to calculate the locations: the RAID controller performance hit under normal desktop use will nullify any gains. And writes will be significantly slower. Most software other than streaming audio and video, use a mix of reads and writes that uses RAID very inefficiently. Does someone know if Apple's OSX software RAID even does split reads?

Think of RAID performance this way.
The BigBox store on the other side of town has the goodies you want at a 20% lower price (faster throughput). If you are buying a ton of stuff at once, or if you are buying one very expensive thing, it's worth the hour drive there and back. If you have to buy something smaller every day, though, the round trip (the RAID overhead) becomes the limiting factor, and you go to your local store instead, even though the price is higher (slower) because you net out to a lower cost.
 
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