Dan wrote: *snip*
>> Should I buy RAID1 units? > > Personally, I'm not fond of using RAID boxes for backup. As I > mentioned in another post, RAID is Fragile. Too many things can go > wrong with it. IMO, it's better to get normal sturdy drive/boxes > that won't mind being lugged about. Agreed, in a way. RAID is NOT a backup solution. It never was designed to be that, and shouldn't be used as such. RAID is a hedge against loosing your data when a drive fails. It will not work against accidentally deleting files or having a piece of software go rouge and start writing the binary equivalent of off colour jokes in Polish on the drive. >> "hardware" based RAID; this is preferred over software RAID? > > Hardware-based is better, either in the controller in your Mac or in > the controller in the box. > > Software-based RAID is... a waste of your Mac's CPU time and i/o bandwidth. I would disagree a bit. Most hardware has enough spare CPU cycles to deal with a software RAID setup (many CPU's on a RAID card are 200 Mhz or so in speed). Besides, what is one going to do when that RAID card fails? Don't forget that most, if not all, hardware RAID cards use a format for storing the data (one can not just drop in a drive from the array in another machine had have it be readable) that is specific to the manufacturer, if not the card and/or firmware revision. Replace it with the same model: Might be possible as the card might be discontinued by then. If replacement is possible, hope that the firmware on the replacement card is compatible with the old card and it's format. If replacement with the same card is not an option, one can try a card from the same manufacturer that is as close as possible to the original card, and hope that it can read the format of the drives. Yes, the chances of this are not high, but they are there. And remember that hardware will always choose the worst time to break down (I think they are in league with Mr. Murphy and his damned laws). Personally, I would rather use software RAID. If Something Bad(tm) happens, all one generally needs to do is reinstall the OS and the RAID is back up. >> I never seem to hear of any home users using RAID1 for their back >> up; what's the reason for this; doesn't a RAID1 unit constantly >> update your backup over two drives as you are using the computer? > > Yes. It immediately copies your errors from your main drive to the > hot backup. Makes the backup useless for normal file recovery. *nods in agreement* RAID is not a backup solution, it is a data redundancy solution in case of drive failure. If something starts writing random data/garbage to the primary drive through the normal API's, the RAID system is going to do what it's supposed to do: Copy that data to the secondary drive(s) in the array. It can't tell what is Good Data vs Bad Data, it just sees a change and duplicates it on the rest of the drives in the array. *snip* > Note that there is no such fast update for RAID1. Because it is > block-level, it will have to re-write the whole drive every time you > reconnect it. Some RAID hardware is a smart enough to read both > drives and compare the data and only write what's needed... but > still, it requires reading EVERY block on both the drives... *snip* I can add confirmation from personal experience on this. At work, we have a Dell PERC/6 RAID card (not my choice) running a RAID 1 using 78 gig 15K SAS drives. If I was to pull one of the drives in the array and reinsert it (same drive mind you, not a new one), it will take a few hours for it to run it's consistency checks and rebuild (even for a small change). I could adjust the amount of CU time used for this process, but it would severely slowdown the disk I/O of the system while this was happening. --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed Low End Mac's G3-5 List, a group for those using G3, G4, and G5 desktop Macs - with a particular focus on Power Macs. The list FAQ is at http://lowendmac.com/lists/g-list.shtml and our netiquette guide is at http://www.lowendmac.com/lists/netiquette.shtml To post to this group, send email to [email protected] To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/g3-5-list?hl=en Low End Mac RSS feed at feed://lowendmac.com/feed.xml -~----------~----~----~----~------~----~------~--~---
