USB Hard Drive - MIRRORING

EdinburghGary

EdinburghGary

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Guys,

I have two identical 1TB USB Hard Drives. Do you know of any solution or bit of software which will act as some form of RAID simulator and ensure that when data hits DRIVE01, it is exactly replicated on DRIVE02? I want NO difference between ANY data on either drive, and would prefer it to happen automagically :D

Any help appreciated!

Gary.
 
I thought RAID was more of a hardware thing and dependant on the motherboard not OS, the reason I say this is because I think implementing raid at a software level could be really processor intensive, where as a raid controller chip would take care of the raid while the OS just reads and writes as per normal.

I'd be surprised if raid was possible on usb, and I think they'd be quite a performance hit.
 
Rsync is brilliant.
I implement it in a slightly different way in which you intend to. I use it to back up my Photo's folder on my server to another server every evening. It does exact copies and subsequent changes to files or folders are replicated in the next backup.
It can be used to back up selected folders on one drive to another drive on the same machine with ease.
 
Going from your orginal definition i.e. no differences at all, then you need to be doing hardware raid.

Software raid is ok, but at the ned of the day the only really 100% effective way of doing it is hardware.
 
barneyrubble said:
Going from your orginal definition i.e. no differences at all, then you need to be doing hardware raid.
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um no. file sync'ing is perfectly acceptable and in some ways better.

RAID doesnt let you take 1 drive off site. RAID isnt only maintaining duplicate copies of data that can be used independantly. RAID is not a backup solution.

personally i wouldnt recommend RAID for home use with no 2nd copy of data.
 
Can you not just use them both as time machines and up date them that way.
Then you will the same stuff on both.
Thats what I do on my mac...
 
Suggest you re-read the wording:

RAID simulator and ensure that when data hits DRIVE01, it is exactly replicated on DRIVE02? I want NO difference between ANY data on either drive
Click to expand...

That is RAID and not synching. Big difference

No mention of moving stuff off site. Mention of RAID. Synching is not RAID (again).

You are reading more into the requirements than is said. As I said going from your original requirements and not reading stuff that's not there :D:D

And thanks for the lesson on RAID. However, once again, no mention of this being used in a backup strategy. He specifically he wants two copies of the data, not for what reason. If you want resilience for data availability reasons (which appears to be what is required here) then RAID is best.

However, if gary would like to flesh things out a bit more with the requirements then my recommendation may change, however at the moment, with the information already posted, hardware raid is the best solution.
 
barneyrubble said:
Suggest you re-read the wording:



That is RAID and not synching. Big difference

No mention of moving stuff off site. Mention of RAID. Synching is not RAID (again).

You are reading more into the requirements than is said. As I said going from your original requirements and not reading stuff that's not there :D:D

And thanks for the lesson on RAID. However, once again, no mention of this being used in a backup strategy. He specifically he wants two copies of the data, not for what reason. If you want resilience for data availability reasons (which appears to be what is required here) then RAID is best.

However, if gary would like to flesh things out a bit more with the requirements then my recommendation may change, however at the moment, with the information already posted, hardware raid is the best solution.
Click to expand...

i know how raid works thanks. ive got 20+ servers and a SAN at work.

in fact most syncing programs can be set to replicate the data pretty much instantly. anyway last time i checked you cant hardware RAID USB and software RAID i wouldnt touch with someone elses bargepole.

yes i know no one mentioned backups etc however at least 1 person suggests that RAID is the be all and end all of backup solutions when in fact its not. i was just getting in there first.
 
I'm currently in the middle of a BCP test - failing over 260 servers from one datacentre to the other, about 20 miles apart, most San attached, some physical with RAID 5 data and RAID 1 system disks. However, even though all servers have some form of raid, they are also backed up offsite too. We don't start one of these exercises until all backups are completed.

So I agree that RAID is not remotely a backup strategy. For those who don't understand RAID, as soon as a file is deleted or corrupted on one disk, the same happens on the other.

I would argue that any software that can be set up to do something "pretty much instantly" can also fail like software RAID. Take worst case scenario.

You are writing a file to the disk. Before the synch software can do anything, that write needs to finish. before the write finishes that disk fails. At this point you've lost that data, thereby being unable to synch it. Hardware RAID and it writes to both disks simultaneously and the second write continues even if the first disk fails.

The statement Gary made:

I want NO difference between ANY data on either drive
Click to expand...

can only be garunteed by hardware RAID. However, as you correctly stated - you can't hardware RAID two USB drives, so the only solution to that is get a USB RAID enclosure and take the 1tb drives from it and install in the enclosure. Expensive yes, but meets the requirements. If we are going to take what Gary has said literally then this is the only solution.
 
barneyrubble said:
You are writing a file to the disk. Before the synch software can do anything, that write needs to finish. before the write finishes that disk fails. At this point you've lost that data, thereby being unable to synch it.
Click to expand...

nope not lost at all its still on disk 1 ready to be sync'd to disk 2.

Hardware RAID and it writes to both disks simultaneously and the second write continues even if the first disk fails.
Click to expand...

unless the RAID controller fails rendering both disks unreadable. forcing a restore from your backup method. (yes it does happen)
 
nope not lost at all its still on disk 1 ready to be sync'd to disk 2.
Click to expand...

No - read it again - Disk 1 fails during the write - data gone.


unless the RAID controller fails rendering both disks unreadable. forcing a restore from your backup method. (yes it does happen)
Click to expand...

RAID controllers do fail, however, if you get a decent raid controller then the RAID info is actually written on the disk, so will work on another controller too.

I've tested this by moving RAID 5 disks around within an array, which in the past would have rendered the RAID invalid,now works like a dream.
 
barneyrubble said:
No - read it again - Disk 1 fails during the write - data gone.
Click to expand...

beg your pardon, mis read.

RAID controllers do fail, however, if you get a decent raid controller then the RAID info is actually written on the disk, so will work on another controller too.
Click to expand...

on the couple of occasions ive seen total loss as a result of hardware happen the controllers were HP server grade ultra320 scsi controllers.

please dont think im being argumentative for the sake of being argumentative. i PERSONALLY do not think RAID is suitable for applications outside of business environments where redundant disks are in abundance and regular backups are taken.

RAID mirroring is certainly no replacement for a good (or indeed any) backup routine.

i appologise if i came across a little harsh or OTT :)
 
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