How to replicate an old server with a 3 disk RAID 5 array ?

[Buzby]

Hi,

I am an industrial controls engineer with a client who needs to replicate a very old server.

The server is a Dell 1750 Xeon 2.8Ghz 1 Gb RAM, with three removable 73Gb SCSI SCA drives operating as RAID 5 using a PERC 4/Di controller. The OS is Windows Server 2000, and the application softwares are of the same era, with flakey original CDs. There is no internet connection.

The client has sourced the exact hardware components to build a replica, and it will be my job to transfer a copy of the existing system onto the replica. This replica will then be a 'cold standby' which can be manually switched over if the existing server breaks.

There is a specific reason why my client wants to go down this route, and not upgrade or use a VM solution. The server is part of a validated system running a pharmacutical process, and the cost of re-validating a 'different' system will be excessive, and the 'cold standby' solution is only needed for a couple more years.

My idea is to replicate the three drives by swapping each one at time, letting each new drive rebuild before swapping the next. After a few hours I should have three drives ( or just two at first ) which can be plugged into the 'replica', thus duplicating exactly the original.

I'm not an IT guru, and don't know much about RAID, so I don't know if my idea will work.

Does it sound feasible ?.

If not, what is the best method to clone the system ?.

Cheers,

Buzby

 

[CiPHER]

If you make a 1:1 clone of the drives and insert it in the backup 'cold' system, it should pickup the RAID metadata and all should work. Making the 1:1 clone is best achieved using a non-Windows OS (Linux/BSD) and using a raw cloning application such as simple 'dd' - part of any UNIX-like system.

dd if=/dev/drive1 of=/dev/drive2 bs=1M

Repeat for all three drives, and you have your cloned RAID array. Beware though that you need the correct drive names, and are not copying to the wrong drive.

 

[Buzby]

Do you mean I should use a separate UNIX PC to clone the disks one at a time ?.

What is the problem in my idea of using the existing RAID to build the new disks ?

 

[dave_the_nerd]

Do you mean I should use a separate UNIX PC to clone the disks one at a time ?.

No. Your use of a hardware RAID controller means you can't do that.

What is the problem in my idea of using the existing RAID to build the new disks ?

Likelihood of RAID failure during rebuild.

Build the new system, and set up a live sync to copy data from the old one to the new one at regular intervals. The "standby" is useless if the data is months or years out of date.

 

[Carson Dyle]

Is this system going to be in use during this time? I would hope not.

I take it there's no data stored on the machine? If there is data on it, then the replica wouldn't really be a swap-in backup, as the data would be lost.

I have no knowledge of what you're talking about in regard to the validating of the hardware, but are they certain that building a replica system from the same old components will make it "validated" by whatever governing body oversees such things? You mention the cost of validation, but it sounds like a process with lots of hoops to jump through, "i"s to dot and "t"s to cross. Doesn't strike me as something where you just slap together components, even if they're supposedly identical, and the system is immediately considered validated.

In theory, sounds like your plan should work, but to my thinking it sounds dangerous. Surely there must be software that can clone a RAID array. Or just take the system offline and make hardware clones of each disk one at a time.

 

[[DHT]Osiris]

My idea is to replicate the three drives by swapping each one at time, letting each new drive rebuild before swapping the next. After a few hours I should have three drives ( or just two at first ) which can be plugged into the 'replica', thus duplicating exactly the original.

Most likely won't work. There's probably some functionality built into some raid controllers/programs to 'rebuild' stuff it sees, but generally hardware goes wonky if it didn't build the array. I just wouldn't trust that to work out the gate like you want.

I'd be very nervous about cloning individual drives entirely in fact, via any method, especially one that takes the system offline. Your best bet would to be to build the array on the second system, to the point where you've got a 'disk space' available that matches the original (the 73GB available or w/e), then find a way to backup/restore the data onto the system from the old one. Basically, pull it up a layer from 'block level/hardware level' to 'software level'.

Did a brief googling, looks like there's a few utilities which still support 2000 fine. Odds are good you can do a full restore without actually installing the OS first (which gets squirrely on the best of days).

 

[CiPHER]

Do you mean I should use a separate UNIX PC to clone the disks one at a time ?.

What is the problem in my idea of using the existing RAID to build the new disks ?

You can use the same system by using a Linux USB-stick, for example Ubuntu. After having booted, Ubuntu will see the physical drives that you have connected to the chipset SATA instead of the RAID controller. Then you can copy the contents off of it. Then you can connect the new disks to the controller. The controller should not make any difference between the original disks and the new cloned disks. Just make sure you keep those two separate; either connect the 3 original disks the RAID controller or the 3 cloned disks; not any combination of them.

One even easier method is to buy a single large disk, and copy the entire contents of the RAID array to that disk. In this case, you do not need a RAID controller in your cloned system. Just one big harddrive will do, if it is large enough. If you have 3 disks in RAID5 where the disks are 2TB large, this means your volume is 4TB large and thus you need a single disk of 4TB big. Of course, your cloned system in this case will not have any redundancy.

No. Your use of a hardware RAID controller means you can't do that.
Why not? All RAID configuration is stored in the 'meta-sector' - the last sector on each harddrive. So i see no reason why this should not be possible. Of course, one needs to connect the disks to another controller temporarily to get access to the physical disks. Some controllers have a HBA-setting, sometimes called JBOD. This makes the controller behave as a normal HBA controller without RAID functionality. But if you connect the disks to the chipset SATA controller - temporarily - all this is not necessary. It also won't be necessary if copying the contents directly off the RAID volume to a single harddrive, thus removing all RAID configuration.

 

[dave_the_nerd]

Might work. Depends on the RAID controller.

What are the uptime requirements for this system during the cloning process?

 

[Buzby]

Thanks for all the replies.

The plant has been running 24/7 for over 12 years. It does not store data at all, there is a totally separate ( and much more modern ) dedicated data logger.

The client has been a bit slack in plant investment, basically working to the principle of "If it ain't broke don't fix it."
It was when I was onsite for a different reason that I spotted a red light on one of the drives. The faulty drive was replaced, but the incident kicked off a panic, and now they want a disaster recovery option ASAP.

Regarding validation, the client has had negotiatons, and a 'like for like' replica is acceptable. There will still be some validation requirements, but much less than any other option.

Although I would like to keep the system running during the cloning operation, it's beginning to look from the replies above that I might need some downtime. This can be arranged, but it will need at least a months notice.

It's looking like I have two options.

1 Build the replica hardware, find a utility to backup the original to a single big disk, then restore to the replica, letting the RAID sort itself out.

2 Boot from a UNIX Live CD, backup each disk individually, boot the replica from a UNIX Live CD, then restore individually.

I'm going to need to investigate both these options carefully. There is a difference in the processes. Option 1 is copying at a level 'higher' than the RAID controllers, and Option 2 is working 'below' the RAID controllers.

Thanks for all your help, I'll let you know how it progresses.

Cheers,

Buzby

 

[[DHT]Osiris]

1 Build the replica hardware, find a utility to backup the original to a single big disk, then restore to the replica, letting the RAID sort itself out.

I really, really recommend attempting this first. It shouldn't require any downtime, and shouldn't really affect the host system in any way (other than HD IO while you back up). The other option requires downtime, potentially removing disks (how stable is the RAID/raid controller? Will it care if you rip disks out?) and has a higher potential to not work on the new system.

 

[Buzby]

I'm tempted to do it this way, but there are a few questions.

Is there a Live CD utility than can read the RAID disk as a whole, as previous comments seem to indicate that a Live CD would see the three disks separately ?.

If I can't use a Live CD then I'll need to install something on the server to perform the backup. It's Win Server 2000, and I've not found anything yet that definitely works on this OS. Also, if I need to install something I'd prefer a very small footprint, like an agent, with the main utility running on a different machine. What would you recommend ?.

Cheers,

Buzby

 

[dave_the_nerd]

What is the raid array / volume being used for? Boot drive? (this may change the preferred cloning method.) What is the data you need to clone (client data) vs. data that you're just cloning because you're lazy? (OS install, applications you have installer disks for, etc.) Not that there's anything wrong with being lazy, but... yeah. If all you _really_ need to do is install Windows and copy a single directory full of files, well, for crying out loud, just do that.

If you boot from a LiveCD, the RAID controller will still present the single RAID volume. clone to disk image, then copy the disk image to the new RAID volume on the other system... will probably work if all the hardware/firmware is the same.