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View Full Version : RAID help please!


florio
Sep 15, 2005, 08:07 PM
Hi,

I have a few questions about Mirrored RAID. Apple's Tech support will not answer any questions without a $250 fee, because they deem it to be a "Pro" question.

Anyway, here I go.

1. I have two hard drives, both partitioned ("A" One internal SATA 100GB, and "B" one external firewire 160GB). I want to install Tiger on one of the partitions and have it mirrored. When I setup the RAID and try installing the OS on the new mirrored array, it says that the computer cannot startup off that disk. Am I doing something wrong or is this really the case? I can't believe that I can't mirror a startup disk for backup?

2. Also, can I not setup a mirrored RAID with both partitions. Both drive "A" and "B" have two partitions named say "Video" and "Audio." I create a mirrored RAID with partitions "Video" from both drives. If I then try and create a Mirrored RAID with partition "Audio" from both drives it will not let me. Can you only mirror one partition per drive or am I again doing something wrong?

3. Is there any way to preserve info on the drives when creating a new RAID array? I don't think so, but maybe?

4. Should I be setting these up the Mirror RAID with the partitions being "RAID Slices" or "Spares." I have no idea what that means.

5. Should I just leave the mirrored array block size at a default of 32K? For Video work is it worth bumping it up to 128k or 256k?

6. Lastly, when I create a mirrored RAID, the icon showing for the "new drive"
is for an firewire drive. Does this mean that when i read the data, that it is coming from the external drive and not the internal one. Can I set which one the computer reads off of? Does it read off both? I have no idea.


Thanks,

Florio

Eniregnat
Sep 15, 2005, 10:10 PM
Before we got to far, I am posting what I can, as well as questions and suggestions so that others can better comment on your question. I should be able to provide a start. Second, I admin a few large RAIDS, one of which is doubly redundant, that is internally each of the servers is RAID5 and each of the servers is mirrored. I work as an audio monkey, video editor, as well as the administrator for a few networks. I've been working with editing audio and video for over 7 years.

First off, Why do you think that you need a RAID to store your clips and rendered product? What exactly is your set up. A good practice for non-linear editing is that your system scratch and program source be on a different drive than your clips. Best practice (debatable) is a separate drive for your system scratch, your clips, and your renders. It's even better if you can have your applications scratch in a separate location.

If your using FCP, the recommendation would be to put your video and audio clips in different bins. Those bins can be pathed to separate folders on what ever drive you want it to be, but you really don't have to as the bins. I might suggest having a folder on a drive labeled Clips, and with in it have Video, Audio, Rendered, Composites etc... Then path the bins from there. What ever it is, keep it simple. You don't need to place your audio and video clips in different partitions or drives. Though if you have the cash, cool. Just some thoughts.

In searching the forums there are not a lot of recent threads about RAIDing using OSX unless it concerns Xserve. Below are some links.

This is a basic information about RAIDS from some of the MacRumors members. (http://forums.macrumors.com/showthread.php?t=146999) and another one (http://forums.macrumors.com/showthread.php?t=27292). Mc68k posted this link about RAID (http://storagereview.com/guide2000/ref/hdd/perf/raid/index.html)s and hd in general.

And some points that CrackedButter (a great member) asks about RAIDS (http://forums.macrumors.com/showthread.php?t=136712).

Backwards, and as best as I can.

#6- you can change the icon. It makes sense as the drives are conjoined. It is both an internal drive and an external drive. If I were the designers, I would note the weakest link which is the FW. Unmount or disconnected the drive and you break the RAID. (DRIVE HAS FALLEN OUT OF RAID) You will have to rebuild it. DiskUtility only offers limited RAID support in the non-server based OSX. So get used to command line if you have problems.

5#- The smaller the block size the more efficient it is for lots of small files (correct me if I am wrong). Larger block sizes should improve speed for mirroring video. If you were to use redundant RAIDING across multiple drives, the smaller size would be more advantageous for a quick rebuild, but not for cataloging. Somebody else, chime in.

4#- Personally- Hotspare- rebuild is a bitch, no matter what, but I guess you are shooting for uptime, even if degraded.

3#- Have at it. (http://www.afp548.com/article.php?story=20040827122302975) The simple answer is not easily- so no. There are pay utilities that can do it, as well as OSX tools.

2#- You really don't need partitions for both audio and video. You are limited in the kinds of setups you can do with the basic tools provide for in the non-Xserve version of OSX. One of the limitations is that mirrored partitions have to be of equivalent size, so do the drives. The smaller drive is always the LCD.

1#- Most MIRRORS are not backups. Information is mirrored across both drives. While a computer can operate off one of the drives, the information has to be present on both of the drives. (Go with me on this one.) So you have to install OSX on the aggregate drive. Then if one of the drives fails, and you can't rebuild, i.e. the other drive is dead, you will have to fix the drive with the DriveUtility or command lien to not be RAIDed.

Now- this is to the best of my understanding. I am not using any OSX RAIDS now. I stay away from RAIDS in my personal world. I prefer good backups, run over night while I am sleeping. Rebuilding a RAID is a long process! RAIDs can be a pain in the ars. The storage servers I work with use a unix and JAVA based os, with automatic tools. Despite this, working with hotswapable drives and rebuilding even partitions of drives takes time and slows the studio down. A redundant 1Tb rebuild took 22 hours once! Dude, that is a long day!

Cheers. I would look around the forum for working video editors to get their advice. Their lives depend of coherent clips and no crashes.

It's late, I'm tired, and I am going. I hope others chime in. Cheers.

Post Script: For me, I am rubbed the wrong way when somebody posts 'Please Help!' when there isn't an emergency. Also, I could better forgive the posting in more than one forum if it had been an emergency. Sorry- I have been doing reviews for the staff this week and I am tired and cranky, and feel like giving a lecture.