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RAID questions… - john-o - 09-01-2006
I did some searching, but what I found was pretty sketchy.
I currently have two new Seagate 320GB SATA drives (model #ST3320620AS; the newest SATAII with "Perpendicular Recording Technology") in my G5/dual-2GHZ (second rev., I believe). I took the two older 160GB drives that were in the tower and put them in a dual-drive SATA case from OWC and installed a FirmTek SATA controller card in the G5 as well.
I've been trying to learn more about RAIDs, but with minimal progress. From what I've read, I would get a noticeable speed increase if I made the two internal drives into a striped array (RAID 0?), but I would then have to make sure I had good backups since that setup would be hosed if either drive failed. Am I on the right track so far?
Specific questions:
1) I currently have the two internal 320GB drives setup with one as boot drive and the other a clone of that; there is ~160GB of data on each. How would I go about making them into a RAID 0 setup? I'm guessing I'd have to clone the startup drive to an external, create the RAID, then restore from the clone. Is this correct? Are there tips I should be aware of in attempting this?
2) My temptation would then be to have the two older 160GB drives setup as a mirrored array as a backup of the boot-drive striped array. Even though the startup drive would be much larger, I could back up my music and video libraries separately (which total around 75 gigs), and I'm sure I'd have plenty of space for the remaining files. Does this make sense to you?
3) Any and all advice/resources for learning more about this would be very much appreciated. I'm already leaning towards buying SoftRAID, since it sounds like the tool to have if you're going to be working with RAIDs much at all. Is there anything else I'm missing?
Thanks very much in advance,
John-o
Re: RAID questions… - jdc - 09-01-2006
what are your doing with your mac that you might benefit from a RAID?
Re: RAID questions… - john-o - 09-01-2006
Hey jdc, shoulda known you'd be the first to respond...
To answer your question, I'm doing just about everything with this computer, from basic internet to digital image processing as well as video editing/processing. I'd just like to get the fastest disk performance possible, if it's not that hard to do, given that I have plenty of capacity.
Make sense?
Re: RAID questions… - mattkime - 09-01-2006
It sounds like you're getting most of the ideas right. However, i agree with jdc - what kind of work do you do?
Re: RAID questions… - john-o - 09-01-2006
Matt,
As I said above, I do a little bit of everything. Wouldn't I see a boost in doing things like video processing? I also remember seeing a reference to the entire computing experience feeling much faster with the striped array.
Why wouldn't one want the best performance possible??
Re: RAID questions… - ztirffritz - 09-01-2006
I've found that Wikipedia has a very thorough description of RAID. For most home/small office use RAID 0,1 and 5 are probably most common. RAID 0 gives performance, but actually decreases the reliability because if one drive failes you're screwed (remember those Lacie BigDisks?). RAID 1 is simply mirroring. You are limitted to the size of the smallest disk in the array. RAID 5 is going to be expensive because of the number of drives, but it gives redundancy and reliability. You can still function with a single bad drive and it can be rebuilt on-the-fly if all fo the pieces are hot-swappable. If you lose 2 drives you're screwed though.
http://en.wikipedia.org/wiki/RAID
RAID 0
A RAID 0 (also known as a stripe set) splits data evenly across two or more disks with no parity information for redundancy.
RAID 1
A RAID 1 creates an exact copy (or mirror) of a set of data on two or more disks. This is useful when read performance is more important than data capacity. Such an array can only be as big as the smallest member disk. A classic RAID 1 mirrored pair contains two disks, which increases reliability exponentially over a single disk.
RAID 5
A RAID 5 uses block-level striping with parity data distributed across all member disks. RAID 5 has achieved popularity due to its low cost of redundancy. Generally, RAID 5 is implemented with hardware support for parity calculations.
Re: RAID questions… - mattkime - 09-01-2006
>>Wouldn't I see a boost in doing things like video processing?
Not likely. Disk speed is rarely the limiting factor.
>>I also remember seeing a reference to the entire computing experience feeling much faster with the striped array.
I believe that, but I doubt it would be enough to make it worthwhile.
>>Why wouldn't one want the best performance possible??
Because it comes at the price of unnecessary complexity and cost.
Re: RAID questions… - ztirffritz - 09-01-2006
[quote john-o]Why wouldn't one want the best performance possible??
Remember, the more disks you have the higher the odds that one will fail. If you don't design the RAID system correctly to match your needs, you will exponentially increase the odds of a disk failure resulting in catastrophic data loss. If you need speed more than reliability and you religiously make system backups a striped system may benefit you. But if you will loose $10,000/min because of down-time while you restore from a backup and replace the damaged hardware striping is definitely not a good idea unless you do it properly with redundancy and reliability included.
Re: RAID questions… - The Grim Ninja - 09-01-2006
You cannot boot a software RAID.
Ever.
I would suggest you take a 320 for the startup disk. RAID the two 160's into a 320 GB drive (less formatting) and use that volume for scratch disk. Backup to the other 320 GB drive.
If you have money, just buy a newer big drive that will probably be faster than the RAID anyway, and use it.
Re: RAID questions… - john-o - 09-01-2006
Okay, this is interesting. Sounds like some of you don't think there's enough potential performance gain to be worth the time, money and effort to do this. If that's the case, would it not be worth making at least the two internal drives into a mirrored array, for redundancy? What are the downsides of doing that versus some sort of backup software that would do the same thing? SuperDuper or Chronosync or the like...