Yep, worked with LVM on Linux, along with similar concepts in the hardware RAID arena as well. And yes, I do understand that RAID is a block level operation, and thats where my issue with it comes it. It can be great for many applications. But I think for home use, something that works at a file level can be much more beneficial to use. Going to a file level redundancy easily avoids any mess with LVM or any other methods for avoiding the complicated setups to workaround the base concepts of RAID.

So far, my best impressions of storage products (be it Linux RAID, or hardware devices) has always been better the less I must know about the inner workings of the solution to set it up and operate it on a daily basis. (Probably a loaded statement there, since my last one gave the impression I don't know about RAID ) The EVA storage line was really fun to work with at my previous job. It was this big rackmount system, capable of going up to 252 disks. As for setup, there were definitely optimal ways of doing things, but the hardware took care of it. To create a virtual disk to share out over the SAN to servers, you simply told the controller that you wanted an X gb sized vdisk, with redundancy like RAID 0, RAID 1, or RAID 5. You didn't tell it what physical disks to store the data on, instead the controller would decide where the most optimal place was, in terms of both performance and redundancy. With 18 different disk shelves it would usually favor spreading the data across as many different ones as possible This was done to ensure that if an entire shelf went down, data was still there and accessible. It also would migrate data around as the configuration changes. So if you started out with only 6 shelves, then added 2 more later with disks in them, the controller just took care of migrating data. And the disks inside never had to be the same size. So it was a great system to allow expandability, either over a period of weeks, or a period of years when drive sizes have increased dramatically.

This is part of it but not all, I don't think. I do like the "less complex" part of anything.


Indigent?


Part of my feeling comes from my sense that while many folks should know that RAID != backup, in practice folks get a little lax or forget that they have a RAID config that could fail. In the past 5 years I have seen 7 to 10 postings to mail lists both inside and outside my employment sphere of cries for help to the effect "My RAID 5 is hosed! Does any body have a XXX controller? Does anybody know how to (fill in the blank)?" I think I remember at least 1 Proliant (no idea of actual controller make) and 1 3Ware in these posts. From what I could tell, most of these ended unhappily. A couple were not backed up.

Anyhow, folks used RAID5 with some combination of disks that would be considered small by todays standards (36GB SCSI drives, say) to get a total volume yield that was not attainable in any other way. 300, 500, 750GB or 1TB drives weren't in the picture when some of these were set up, but some of these folks would be completely set for the next decade with 300GB available disk for a given application and they would not need to go to a parity RAID solution to get that.

I also see pretty regular queries fo folks looking to find spare 9, 18 and 36GB SCSI drives to repair or maintain RAID sets that were created man moons ago and that are locked to a particular drive size.

I have an example of backup server that is a 16-drive-slot chassis, but which presently has 8 slots free. By only adding disk as needed (in pairs) we can wait for prices on 1TB drives to sink or wait for 1.5 or 2TB drives. Not locked into the previously affordable drive size.

Anyhow, my arguments are not what I would call scientific. I have a 3TB RAID5 NAS in my care and that is just fine. I don't need same at home. I can't seem to fill up my 500GB mirrored drive set. Using your 3TB example, though, my solution would be to get 2 1TB drives today and then add 2 2TB drives in 2010

I have seen at least one case where somebody set up a RAID5 where I just couldn't fathom why; it was like somebody did it "because I can" or because it was somehow superior. I guess I am on the other end of that opinion continuum.

In fairness, I think at least a few of the "Help! I'm screwed!" email calls for help I cite in last post were folks who only figured out they had a problem when that 2nd drive failed. But I did see one single-drive failure where restore on to a hot spare just would not complete. Also one case where all drives were ultimately shown to be fine but where controller just lost its freaking mind. With RAID1 you have some hope of just plugging a drive in and seeing a file system.

Well, of course. Those pesky meteorites are RAID-agnostic.

Since they don't offer DP, EMC will tell you that NetApp' RAID-6 DP is a bad thing I've had both EMC and NetApp and will say that, on balance, I'd pick NetApp next time. Part of it is that EMC as a company is just way too big. NetApp more focused, easier to navigate support resources. Same end result though: hard drive shows errors....replacement hard drive automatically shows up as if by magic. I checked last week and uptime on the Filer in my old department is 1035 days. Not bad.

When it is time to buy a new NAS in like 2010, I hope I can figure out how to use OpenFiler (or equivalent FOSS product) and achieve the same magical effect.

Somehow I don't think OpenFiler is ever going to figure out the "shows up as if by magic" parts replacement :p

Well, if I lived in the UK, the folks behind OpenFiler would gladly sell me a NAS:

http://www.xinit.com/main/storagenetworking/NAS/sns316012.html

but I can't tell right off whether it comes with Magic(TM).

We buy rack-mount boxes from a local vendor who we hold in very high regard (and who are very FOSS/Linux friendly). We've talked with them about whether they would ever consider an OpenFiler-type solution as a line of business. But supporting core storage with true Magic takes you into a whole different risk profile, so I doubt they are going to do it.

So maybe we will have to survive on ersatz, emulated Magic -- buy a box from them and then keep our own spares around. With our current OpenFiler box, we get email failure notifications both from the controller (3Ware 3DM2) and from Linux MDADM, so it could be worse, but the fault detection/notification systems in top-tier NAS like NetApp set a high bar.

One reason we are motivated to adopt a FOSS NAS is that the commercials NAS are a black box and discussions with NetApp or EMC always get, well, complicated. "What, you say you are running a *Samba* domain? That's really not supported you know old chap!"