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  #1 (permalink)  
Old 2nd April, 2003, 11:02 AM
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Question RAID 1 question

Hey guys

Was planning to set up RAID 1 in a small server box in an office using the Promise FasTrack100TX4 Ultra ATA RAID Controller which features hot swap ability.

My question is:

Say, I've set up the RAID 1 array already consisting of 2 drives and I remove the "mirror" drive 2 bring home, will the server still boot up???

What happens when the primary drive receives additional data at night and I reconnect the "mirror" drive in the morning?? Will the "mirror" drive automatically update itself???

Any tips and things that I should look out for when setting up RAID will be most appreciated. THis will be my first time to set up RAID.

Thanks
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Old 2nd April, 2003, 11:39 AM
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If you remove one of the mirror drives, the mirror array is then broken (or degraded). At which point you've no longer got a mirror, but just a single disk.

Depending on the way the promise works, it may be able to rebuild the mirror on the fly. However, this is a fairly intensive operation, and the machine will operate much slower than normal until the mirror rebuild is complete. Obviously, the length of the mirror rebuild depends on how large the disks are!

Additionally, with hot swap IDE, you need more than just a hot swap controller. You need to ensure that each caddie is connected to a seperate IDE port. (Master/Slave is NOT allowable for a stable IDE hotswap). You also need IDE caddies that specifically support hot swap. The reason for this is that IDE drives are not designed for hot swap. As such, very careful control must be kept of the power and data lines, so that the power/data is sequenced properly. This just means that the ground is applied first and broken last, the power is applied second, and broken second to last, and the data is applied last, and broken first. Failing to do this could potentially destroy a drive and the controller at the other end!

Promise only claim hotswap is available when using their SuperSwap caddies. These caddies also do enviromental monitoring, so the controller is aware of the caddy temperature and fan speed.

Áedán
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Old 2nd April, 2003, 11:50 AM
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Thanks Aedan for the speedy reply

So, basically hot swapping in a RAID 1 array is not recommended. Basing from what I'm planning to do, Backing up the server data and bringing it home then returning it in the morning to update it, any other method that you would recommend over RAID 1??? I was thinking DVD burners maybe...


Oh ya and one more thing.....So if I remove the mirror drive.....it will cause problems with the PC??? So what is the use of hot swap the these RAID card manufacturers are talking about??

Thanks
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Last edited by JayJay; 2nd April, 2003 at 11:54 AM.
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Old 2nd April, 2003, 12:16 PM
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Quote:
Originally posted by JayJay
So, basically hot swapping in a RAID 1 array is not recommended. Basing from what I'm planning to do, Backing up the server data and bringing it home then returning it in the morning to update it, any other method that you would recommend over RAID 1??? I was thinking DVD burners maybe...

Oh ya and one more thing.....So if I remove the mirror drive.....it will cause problems with the PC??? So what is the use of hot swap the these RAID card manufacturers are talking about??
What's the point of hot swap? Well, it's to ensure that there is no downtime when repairing the system after a disk failure. You see, IDE wasn't designed for hot swap, so special precautions have to be taken to ensure things work properly! If you have a caddy that supports hot swap, then those precautions are dealt with!

You see, RAID protects against disk failure. Nothing else. Given disks are probably one of the less reliable physical parts in a computer (due to moving mechanical parts!), this makes sense.

I don't know how much data you have, nor the commercial value of such data. This is what really sets how you will look after the data, and how much you will spend on looking after it. I also don't know the size of the company, or the effects of not having access to the data (latest or otherwise)

Generally a backup system will keep data for a period of time (retention time!) on seperate media. Should invalid data be found at a later date, it's possible to move back through the different versions of files in order to locate the last one with valid data. It's not just simply having a copy of the data from the previous day! (He says, having been asked to restore files that were over a month old before.)

Áedán
(Can you tell I work as a consultant?)
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Old 2nd April, 2003, 12:47 PM
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Quote:
Originally posted by Áedán


Generally a backup system will keep data for a period of time (retention time!) on seperate media. Should invalid data be found at a later date, it's possible to move back through the different versions of files in order to locate the last one with valid data. It's not just simply having a copy of the data from the previous day! (He says, having been asked to restore files that were over a month old before.)

Áedán
(Can you tell I work as a consultant?)
An excellent point indeed. A point which I shouldn't have forgotten.

Thanks so much for the advice.
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Old 2nd April, 2003, 03:27 PM
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Quote:
Originally posted by JayJay
Thanks so much for the advice.
Not a problem. Things like backup take quite a bit of thought to get right, and working in a properly useful manner!

Áedán
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