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View Full Version : OSX RAID? Dual/Single? Why mirror? Why not?



mik
11-14-2001, 02:41 PM
Kaye,
Thanks for your e-mail! Sorry for the slow reply, I am posting here on the forum. I am probably going to go with the ATTO ULD2 card and a couple of 15K cheetah drives in the G4. Since this is the first time I have ever set up a RAID system I have some questions regarding that move. BTW I get my unused G4 800DP back today after a new logic board, (not needed) and hard drive, (the real problem)...Just proves that some Apples start out as lemons. I actually think the root cause was my using HDST to initialize the drive and partion it. Can’t prove that though. There have been some forum comments on this. On to the RAID questions.

1. I plan on going to OSX as soon as Photoshop supports it. SoftRAID is not OSX compatable yet. Soon we all hope... Til then perhaps the OSX RAID software will be sufficient. Anyone on the forum used it yet?

2. Regarding number of drives....If I want to increase the security of my data on a RAID array is the best option to have four drives, two per channel on a dual bus card. The first channel contains the striped volumes and the second channel would have the mirrored volumes. SoftRAID supports simultaneous writes and with mirroring, (don’t know what OSX supports) According to SoftRAID’s website this can increase performance from 5 to 25%, which seems like a considerable amount and adding the additional plus of data redundancy. Is this correct reasoning?

3. If the above is true and I want to have the striped volumes mirrored. Is it a mistake to have only a single SCSI channel with two drives. Even after partitioning the two drives to create separate volumes for striping and mirroring...they would not be able to write to both the striped volume and the mirror simultaneously. I am assuming that no drive can write to two volumes on the same drive simultaneously. If true would this be a serious performance hit?

4. If there are only two drives on a single channel can one drive be striped and the other be the mirror?

5. Is mirroring in a RAID important? In my world (450mb photoshop file) usage is mirroring really necessary? If a disciplined backup procedure is used where each days data is copied to another disk, either firewire or an ATA disk,...or even burned to a CD-RW. Some of these backup options could be programed to automatically take place before shutdown. I do these things anyway.

6. What effect do system freezes and subsequent restarts have on a RAID system. Say in the middle of working with a photoshop file. Besides losing whatever has not been saved to disk do such system lockups pose any risks to data previously saved to the array.

As always thanks to all and their comments....and had I not discovered the MacGurus site I would probably be a PeeCee. Mikel

ricks
11-14-2001, 05:22 PM
Give me a couple of days to set up and test the OSX RAID. I just got back from repair (thanks LV) my second IBM 60GXP drive, so I now have a pair again. I have installed it and partitioned the repaired one into four partitions. I need to transfer out all the operating files from the other 60 GXP and partition it identically. Then I will setup and test Striping and mirroring on those two drives. I'll do this on the Quicksilver 867, maybe on the B&W.

I found some compatability problems with running ATTOs benchtest program in classic mode. My results were definately not reliable. If anyone has a idea of what I should use to quantify the raid let me know. I will try Intechs and macbench.....any others?

Rick
Speed is its own reward.