#294366 - 27/02/2007 14:50
RAID question
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carpal tunnel
Registered: 20/05/2001
Posts: 2616
Loc: Bruges, Belgium
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Hi all,
I was wondering if RAID is a standard. In other words: if I create a RAID array with the disks connected to a certain adapter, can I then connect these disks to a different adapter and will this adapter also be able to read this RAID array? Or does each manufacturer add his own bells and whistles to their RAID adapters, forcing you to stay with their brand?
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Riocar 80gig (010102106) - backup
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#294367 - 27/02/2007 14:53
Re: RAID question
[Re: BartDG]
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carpal tunnel
Registered: 18/01/2000
Posts: 5683
Loc: London, UK
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Quote:
can I then connect these disks to a different adapter and will this adapter also be able to read this RAID array?
Not normally, no.
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-- roger
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#294368 - 27/02/2007 15:21
Re: RAID question
[Re: Roger]
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carpal tunnel
Registered: 20/05/2001
Posts: 2616
Loc: Bruges, Belgium
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That's what I feared. This is the reason I'm still a bit unsure wheater or not I want to use RAID. 
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Riocar 80gig (010102106) - backup
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#294369 - 27/02/2007 15:49
Re: RAID question
[Re: BartDG]
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carpal tunnel
Registered: 25/12/2000
Posts: 16706
Loc: Raleigh, NC US
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If that's a concern, you might want to consider software RAID. While it might be imposible in the future to find a "compatible" controller, it should always be possible to install an old version of your RAID software.
That said, RAID does not prevent you from having to create backups. It is only there so that you can need them less often due to disk failures. You should always count on needing a separate backup, in which case, the failure of a RAID controller (combined with the inability to find a compatible replacement) is simply one of the fewer instances where you need to restore from backup.
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Bitt Faulk
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#294370 - 27/02/2007 16:38
Re: RAID question
[Re: wfaulk]
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carpal tunnel
Registered: 20/05/2001
Posts: 2616
Loc: Bruges, Belgium
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Thanks Bitt. I was actually thinking about buying a readyNAS NAS server by Infrant. And this device also used RAID, that's why I was asking. I was also planning on using a separate external HD with it (it's got USB ports as well), for the extra backup, since I know RAID doesn't protect you from viruses etc.
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#294371 - 27/02/2007 16:44
Re: RAID question
[Re: BartDG]
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carpal tunnel
Registered: 20/12/1999
Posts: 31600
Loc: Seattle, WA
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Quote:
Or does each manufacturer add his own bells and whistles to their RAID adapters, forcing you to stay with their brand?
It's worse than that. I had a friend whose RAID card died, and the exact same card was no longer available. Buying the next card in the line from the same manufacturer turned out to be useless, as it had a completely different way of formatting the drives. He literally lost all the data on the RAID.
RAID is not a panacea. RAID does not allow you to skip backups. In fact, in my opinion, RAID increases your need to make regular backups because it increases the number of possible failure points related to the data you've stored on it. It also increases the likelihood of individual disk failure because you usually cram the drives tightly together into a case, increasing the heat. (So don't ever build a RAID unless you have a cooling fan blowing on the drives.)
RAID has only a few actual uses in my opinion:
- Making a large single volume that is bigger than the largest available disk drive.
- Faster data access.
- Ability to have continuous uptime when a single hard disk in the array fails (at the expense of heartburn and worry as you pray for no additional failures while waiting for the replacement drive to be shipped).
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#294372 - 27/02/2007 17:06
Re: RAID question
[Re: tfabris]
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carpal tunnel
Registered: 19/01/2002
Posts: 3584
Loc: Columbus, OH
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Quote:
at the expense of heartburn and worry as you pray for no additional failures while waiting for the replacement drive to be shipped).
That's why I order one more than I need and leave it on the shelf in the ESD bag. If one were to die, I'd swap it immediately and order a new one for the shelf.
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~ John
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#294373 - 27/02/2007 17:12
Re: RAID question
[Re: tfabris]
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carpal tunnel
Registered: 24/12/2001
Posts: 5528
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Quote:
RAID is not a panacea. RAID does not allow you to skip backups.
That is because it isn't a substitute for a backup system. Many people think it is for some bizarre reason. Even if you mirror your data amongst 5000 drives it doesn't prevent you pressing delete on the wrong file or formatting the wrong partition.
Quote:
- Making a large single volume that is bigger than the largest available disk drive.
- Faster data access.
- Ability to have continuous uptime when a single hard disk in the array fails (at the expense of heartburn and worry as you pray for no additional failures while waiting for the replacement drive to be shipped).
These are the reasons for using RAID. Nothing else.
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#294374 - 27/02/2007 17:14
Re: RAID question
[Re: JBjorgen]
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carpal tunnel
Registered: 24/12/2001
Posts: 5528
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Quote:
Quote:
at the expense of heartburn and worry as you pray for no additional failures while waiting for the replacement drive to be shipped).
That's why I order one more than I need and leave it on the shelf in the ESD bag. If one were to die, I'd swap it immediately and order a new one for the shelf.
That doesn't always work. If you end up with a defective drive then there is a chance that it is a manufacturing problem and an entire batch might be affected. Since most people buy all their drives in one go and also of the same make and model, it is highly likely that you've got multiple drives of the same batch. *cough* IBM DeathStar *cough*
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#294375 - 27/02/2007 17:16
Re: RAID question
[Re: BartDG]
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carpal tunnel
Registered: 24/12/2001
Posts: 5528
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Quote:
Thanks Bitt. I was actually thinking about buying a readyNAS NAS server by Infrant. And this device also used RAID, that's why I was asking. I was also planning on using a separate external HD with it (it's got USB ports as well), for the extra backup, since I know RAID doesn't protect you from viruses etc.
All of the Infrant NAS units I've looked at actually run Linux software RAID and don't have an actual RAID controller. You can yank the drives and plug them into any Linux PC with the correct version software etc...
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#294377 - 27/02/2007 17:28
Re: RAID question
[Re: BartDG]
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carpal tunnel
Registered: 24/12/2001
Posts: 5528
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Quote:
Quote:
All of the Infrant NAS units I've looked at actually run Linux software RAID and don't have an actual RAID controller. You can yank the drives and plug them into any Linux PC with the correct version software etc...
Really? This is very good news!
Thanks for the info! 
Which model you looking at getting?
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#294378 - 27/02/2007 17:38
Re: RAID question
[Re: tman]
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carpal tunnel
Registered: 20/05/2001
Posts: 2616
Loc: Bruges, Belgium
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The ReadyNAS NV+. The only other thing that is holding me back it the fact that I use a D-Link DGL-4300 wireless router which, as far as I can tell, doesn't support Jumbo frames. Since this D-link is one of the best routers I've ever owned, if not THE best router I've ever owned, I'm not really inclided to swap it for something else. Besides, I've yet to see the first router that is wireless, has a 4-port gigabit switch built in and does jumbo frames, all combined into one device... The speed difference that is mentioned on the infrant forums almost makes it worth it though... almost... 
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#294379 - 27/02/2007 17:40
Re: RAID question
[Re: tfabris]
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carpal tunnel
Registered: 08/06/1999
Posts: 7868
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RAID is not a panacea. RAID does not allow you to skip backups. In fact, in my opinion, RAID increases your need to make regular backups because it increases the number of possible failure points related to the data you've stored on it. It also increases the likelihood of individual disk failure because you usually cram the drives tightly together into a case, increasing the heat.
I wouldn't say it increases the need for backup. If a RAID card dies, its the same as having a SCSI or IDE controller die. The hard drive temperature issue is a concern if your building it yourself, but not for systems engineered for holding 14 or whatever drives.
Quote:
It's worse than that. I had a friend whose RAID card died, and the exact same card was no longer available. Buying the next card in the line from the same manufacturer turned out to be useless, as it had a completely different way of formatting the drives. He literally lost all the data on the RAID.
Thats one thing I came to appreciate about the Compaq storage engineers. They realized this situation sucks, and have never caused this to be the case with the RAID controllers in use in the Proliant servers. You could take a RAID setup from a 1995 system running the first RAID controller they made, and plug it into a 2007 card. When Compaq bought DEC, they also began working on interoperability between the servers and external SAN devices. You could take the disks out of a Proliant and plug them into the MSA series SAN enclosures.
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#294380 - 27/02/2007 17:43
Re: RAID question
[Re: BartDG]
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carpal tunnel
Registered: 24/12/2001
Posts: 5528
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The only other thing that is holding me back it the fact that I use a D-Link DGL-4300 wireless router which, as far as I can tell, doesn't support Jumbo frames.
Buy a GigE switch that does support jumbo frames and then plug the D-Link into it?
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#294381 - 27/02/2007 17:43
Re: RAID question
[Re: drakino]
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carpal tunnel
Registered: 20/12/1999
Posts: 31600
Loc: Seattle, WA
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If a RAID card dies, its the same as having a SCSI or IDE controller die.
Interestingly, I've never had the last thing happen to me. I've seen the first two happen.
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#294383 - 27/02/2007 18:06
Re: RAID question
[Re: BartDG]
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carpal tunnel
Registered: 25/12/2000
Posts: 16706
Loc: Raleigh, NC US
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But a GigE switch, plug one port into the D-Link. Plug everything else into the GigE switch. The only thing it won't help with is wireless and your connection to the internet, which will still be going through the D-Link, but you're not going to get the advantages of the speedups from the jumbo frames over the relatively slow internet and wireless connections anyway.
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Bitt Faulk
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#294384 - 27/02/2007 18:26
Re: RAID question
[Re: wfaulk]
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carpal tunnel
Registered: 20/05/2001
Posts: 2616
Loc: Bruges, Belgium
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Ah yes, good point! Indeed, wifi or internet won't benefit at all from gigabit speeds. Soooo.... can anybody recommed me a good switch? (and on the other hand: I'm also thinking about upgrading my father-in-law's home network with gigabit, so for him I could buy a completely new router. Anybody know of a gigabit router that does wireless ethernet and supports jumbo frames?)
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#294385 - 27/02/2007 22:00
Re: RAID question
[Re: tfabris]
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carpal tunnel
Registered: 18/06/2001
Posts: 2504
Loc: Roma, Italy
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Quote:
In fact, in my opinion, RAID increases your need to make regular backups because it increases the number of possible failure points related to the data you've stored on it.
I think RAID simply shifts the critical failure point from the disk to the controller. Assuming you don't have any other issues with cooling system. And, I agree its a very questionable idea that a disk will be more likely to fail than a controller. Maybe that's statistically true but... so what? We don't live off statistics, we live off individual specific cases .
Personally, I too am happy with software raid. I had a RAID5 volume, software-based, on Windows 2000 Server. I removed the three IDE disks and installed them into a Windows Server 2003 machine, newer and completely different hardware. The volume was recognized. I am sure Linux does exactly the same.
Certainly I still need backup, but given that I do a periodic backup, software raid adds a significant protection against data loss due to disk failures. Without a software raid, a disk failure would mean loosing all data since last backup, be it 1 hour or 1 month ago. That's enough to make me spend few extra euros on one extra disk.
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#294386 - 28/02/2007 02:50
Re: RAID question
[Re: Taym]
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pooh-bah
Registered: 20/01/2002
Posts: 2085
Loc: New Orleans, LA
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All the RAID's I have set up at work (except one) have a parity drive and a global spare. If a drive gets dropped from the RAID, the global spare immediately starts the rebuild. In fact, this happened yesterday to my primary AD controller. The only downside to this is that after the failed drive is re-inserted or replaced, you still have to remember to assign it as the new global spare. The single server that does not have a hot spare is my backup server. Since I'm running CPS as well as Disk-Disk-Tape backups, it wouldn't be a big deal to lose the backup server. It can be rebuilt in hours from the disk image I pressed after install. The only thing that would be missing is all the CPS data. Again, not the end of the world.
All that being said, I HAVE had failures of both multiple drives at once, and twice of the controller card going belly-up. In all three cases, the data was completely gone, save for the backup.
I have also lost both regular SCSI controllers (Adaptec 1941) and IDE controllers (many types/brands). In both of scenarios, the data was still intact.
I have had MANY drives fail. I deal with it at least once a month. When you support as many PC's as I do, it's just a numbers game. It's GOING to happen. I'd say that drive failures vs controller failures is 100 to 1 or so, at least in my experience. Keep in mind, a controller has no moving parts. But what it DOES have, is RAM, which is where all my controller failures have occurred (except the IDE ones, which do not have RAM, per se).
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#294387 - 28/02/2007 21:43
Re: RAID question
[Re: BartDG]
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carpal tunnel
Registered: 29/08/2000
Posts: 14496
Loc: Canada
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Quote:
Soooo.... can anybody recommed me a good switch?
The DLink 8-port GigE switch is fanless, metal, and silent.
I'm drooling over the 16-port version of it, but the price for that is too high yet.
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#294389 - 03/03/2007 14:39
Re: RAID question
[Re: mlord]
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carpal tunnel
Registered: 29/08/2000
Posts: 14496
Loc: Canada
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Quote:
The DLink 8-port GigE switch is fanless, metal, and silent.
I'm drooling over the 16-port version of it, but the price for that is too high yet.
Correction. Netgear, not DLink. Duh!
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#294390 - 03/03/2007 23:48
Re: RAID question
[Re: mlord]
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carpal tunnel
Registered: 20/05/2001
Posts: 2616
Loc: Bruges, Belgium
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I've found an 8 port gigabit switch by d-link as well. And a 5-port version. Or is d-link crappy quality?
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#294391 - 04/03/2007 07:36
Re: RAID question
[Re: BartDG]
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carpal tunnel
Registered: 10/06/1999
Posts: 5916
Loc: Wivenhoe, Essex, UK
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One of the appeals of the netgear over the dlink is the metal box, network gear really should come in metal boxes...
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#294392 - 04/03/2007 12:16
Re: RAID question
[Re: BartDG]
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carpal tunnel
Registered: 29/08/2000
Posts: 14496
Loc: Canada
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Quote:
I've found an 8 port gigabit switch by d-link as well. And a 5-port version. Or is d-link crappy quality?
I just like the look of it (as small as it could be, with the 8 8P8C connectors lined up edge-to-edge. And the fact that it is low-wattage and fanless.
Dunno about the Dlink.
Cheers
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#294394 - 05/03/2007 17:49
Re: RAID question
[Re: mlord]
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carpal tunnel
Registered: 20/05/2001
Posts: 2616
Loc: Bruges, Belgium
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Quote:
Quote:
I've found an 8 port gigabit switch by d-link as well. And a 5-port version. Or is d-link crappy quality?
I just like the look of it (as small as it could be, with the 8 8P8C connectors lined up edge-to-edge. And the fact that it is low-wattage and fanless.
Dunno about the Dlink.
Cheers
I see Netgear has also got a 5 port model, which would be enough to suit my needs. After all, I would still have 3 ports left on my 100 base-T router as well for slower devices (like a Karma, Empeg and printer)
Cheers for the info!
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