I don't believe your assumptions are correct. If you go to Drobo.com and use one of their capacity calculators (each model has a different one), your first example yields 5.91 TB of usable storage with single disk redundancy, not 2.5 TB.
If you replace or add a disk, the Drobo will caution you that your data is not fully protected while it regenerates the Beyond RAID but the change in capacity is immediately available. Pretty cool. I read an article on Beyond RAID that conjectures how it works. http://etherealmind.com/drobo-how-beyond-raid-works/ Interesting reading but the author readily admits he's making an educated guess about a proprietary technology. ---------------------- Bob Hartung Wisco Industries, Inc. 736 Janesville St. Oregon, WI 53575 Tel: (608) 835-3106 x215 Fax: (608) 835-7399 e-mail: bhartung(at)wiscoind.com _____ From: Hilderbrand, Doug [mailto:[email protected]] To: NT System Admin Issues [mailto:[email protected]] Sent: Mon, 04 Oct 2010 20:16:23 -0500 Subject: RE: Speaking of Drobo ... (was: SAN question) As I understand it, a Drobo will intelligently use a combination of raid5 and mirroring. If you have one 500 GB, one 2 TB and two 1 TB drives, You’ll wind up with a 3 disk raid 5 across the two 1 TB and half of the 2 TB, plus a mirror of the 500 GB with half space the remaining on the 2 TB drive. 2 TB usable on raid 5 and 500 GB usable on mirror. 2.5 TB total. Pull the 500 GB and put in a 2 TB and it will do a 4 disk raid 5 and a mirror of the remaining 1 GB on each of the large drives. 3 TB usable on raid 5 and 1 TB usable on mirror. 4 TB total. I have no idea how it manages to push the bits around to accomplish that. Or how raid 6 fits into the picture. From: N Parr [mailto:[email protected]] Sent: Thursday, September 23, 2010 8:44 AM To: NT System Admin Issues Subject: RE: Speaking of Drobo ... (was: SAN question) Pretty sure raid on the Drobo defined by the smallest drive in the array. So if you have 3 2TB drive and 1 1TB drive you will only get around 3TB of storage. _____ From: Raper, Jonathan - Eagle [mailto:[email protected]] Sent: Thursday, September 23, 2010 10:36 AM To: NT System Admin Issues Subject: Speaking of Drobo ... (was: SAN question) Ok, so it SEEMS like a really cool device, but I honestly haven’t looked at it seriously since the device first came out a couple of years ago. When I first looked at it, I was like, ok, now THAT’s COOL. However, after thinking about it some, it just seemed like some black magic under the covers to get their “BeyondRAID” to work. When I originally looked at it, I couldn’t find any technical detail on how the product *really* worked, as that was “proprietary” (understandably so, but still, how am I going to get comfortable with it as a sysadmin, especially at the price if I’m on a budget – it would be an expensive toy. Traditional RAID is just much more comforting to me. If you have a big issue with multiple drives of different sizes on a drobo unit, how is data recovery going to go for you? If the controller fails, and you don’t have a support agreement, you can’t just go on serversuply.com and get parts… Does anyone here have any experience with data recovery on a failed drobo, or for that matter, simply a failed drive within a drobo where you had drives of different sizes in the configuration? I know “backup, backup, backup”, but what if the backup doesn’t work (or the customer/end user didn’t heed your advice)? Jonathan L. Raper, A+, MCSA, MCSE Technology Coordinator Eagle Physicians & Associates, PA [email protected] www.eaglemds.com _____ From: Jonathan Link [mailto:[email protected]] Sent: Thursday, September 23, 2010 11:16 AM To: NT System Admin Issues Subject: Re: SAN question +1 Going back to a previous comment of mine in another thread you started. Have you messed with OpenFiler, yet? You'll learn a lot. Also, based on your pretty low requirements, have you looked at the DroboElite? If it had been available when I started looking, I very well could've gone in this direction. As it is, I'm seriously considering it for backup duty. Storage for a backup server, and the ability to use it in a pinch if my EqualLogic goes down. On Thu, Sep 23, 2010 at 10:59 AM, Raper, Jonathan - Eagle <[email protected]> wrote: John - I do not believe that we can help you significantly with this question. In the end, it really doesn't matter what any of us think, because our environments are all different and unique. What works well and may be appropriate for any of us, may be a horrible fit for you and cause you nothing but heartburn and stress. However, I would tend to agree with Niles. If you're not ready for a SAN, don't spend the money on it now. You really need to have a serious sit-down with the vendors/sales engineers (notice I said ENGINEER, not REP) of the different hardware, learn as much as you can from THEM, and ask LOTS of questions. Then ask them why you should choose their product over x, y, or z product. Take lots of notes, and then do the same thing all over again, no more than a few days apart so everything is still fresh in your head. Many times, some of the best education I've gotten has been from the manufacturers themselves. I've actually been to the EMC manufacturing facility in North Carolina - I spent two days there, on THEIR DIME to learn about their products (I had to get there & back, but after that, everything was on them). If you say to them, "I'd like an education on how your product works and whether or not it would be suitable for my needs and my applications.", you'll generally get plenty of intelligent people that will be happy to answer your questions. If they don't ask lots of questions about your environment and what your needs are, you're talking to the wrong people. I believe that the purpose of this list is really a, "I'm having trouble with x, has anyone seen this before?" or "why do you guys think x specification/technology is better than y", or "I'm having trouble getting this ADSIedit script working, what am I doing wrong?". I believe that if you sit down with the various manufacturers/reps, even if only on a webex session where they can whiteboard for you one on one, will answer many of your questions and make your original question about intelligence/disks seem trivial. Regards, Jonathan L. Raper, A+, MCSA, MCSE Technology Coordinator Eagle Physicians & Associates, PA [email protected] www.eaglemds.com -----Original Message----- From: N Parr [mailto:[email protected]] Sent: Thursday, September 23, 2010 10:26 AM To: NT System Admin Issues Subject: RE: SAN question I think you just need to give up on your SAN dreams and go buy a decent NAS for a couple grand and call it good. You just said it's going to be a file server for the time being so why spend the money for a SAN now if you don't need it. I bet if I look back through the archives you first brought this up at least 18 months ago. When, if , you do need a SAN down the road you won't have already spent a ton of $$ on what will then be old tech and you can start looking at what will then be new. -----Original Message----- From: John Aldrich [mailto:[email protected]] Sent: Thursday, September 23, 2010 9:17 AM To: NT System Admin Issues Subject: SAN question Ok, guys. I'm trying to narrow down my many choices with regards to our on-going search for a SAN manufacturer. I'd like your thoughts on the whole question of adding more intelligence vs just adding more disks. i.e. the EQ vs LeftHand models. I can see arguments to be made for both models. I'll tell you that, initially, the SAN is going to be a glorified file server, however, we plan on hosting our email data store on the SAN when we bring email in-house later on. I've already verified with the email vendor that I hope to use that this is not a problem, so that's a non-issue. Other than that, the only database we would store on the SAN would possibly be the database from our Vipre install, although initially that would stay on the local storage. So, I'd like to see some discussions of the benefits of just adding a tray of "dumb drives" or adding a complete controller along with the drives (a la LeftHand.) I just don't know enough about the benefits of each model to know what would work best for us. I'm hoping that you guys who are more experienced would give me the benefit of your knowledge. Thanks, John Aldrich IT Manager, Blueridge Carpet 706-276-2001, Ext. 2233 ~ Finally, powerful endpoint security that ISN'T a resource hog! ~ ~ <http://www.sunbeltsoftware.com/Business/VIPRE-Enterprise/> ~ --- To manage subscriptions click here: http://lyris.sunbelt-software.com/read/my_forums/ or send an email to [email protected] with the body: unsubscribe ntsysadmin ~ Finally, powerful endpoint security that ISN'T a resource hog! ~ ~ <http://www.sunbeltsoftware.com/Business/VIPRE-Enterprise/> ~ --- To manage subscriptions click here: http://lyris.sunbelt-software.com/read/my_forums/ or send an email to [email protected] with the body: unsubscribe ntsysadmin Any medical information contained in this electronic message is CONFIDENTIAL and privileged. 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