RAID in the home, part 2
Posted in Storage Interconnects & RAID, Advisor - Tom Treadway by Tom TreadwayYesterday I wrote briefly about the use of RAID in the home. I think we can all agree that the home contains data worthy of being protected against drive failure. Now it’s just a matter of figuring out how to get ‘er done.
I guess we can start with what RAID traditionally looks like. I’ve been designing controllers and systems with various RAID options for close to 20 years, and I have to say - they’re BUTT UGLY! And they’re not just ugly controllers with a bunch of chips that cost up to $1000. They also have ugly user interfaces. Can you imagine your parents debating the merits of RAID-10 vs RAID-5, and what the appropriate stripe size is for their specific environment? “Honey, should the read-ahead be forced or dynamic?”
Sure, through the years RAID cards have gotten cheaper and GUIs more automated, and of course there are even free options if you wear open toe sandals and shower infrequently. But it’s still not ready for your parents.
So first question – can RAID be an after-market feature, such as with a plug-in PCI card? Assuming cost is low enough, perhaps. But that only works for PC workstations, or servers if you’re a more sophisticated user, that you’re willing to open up. That won’t work for pre-built appliances such as a DVR (digital video recorder) from your satellite or cable vendor. Or a NAS box from folks like Buffalo or LaCie. If those boxes aren’t designed with RAID in mind then you can’t add it after the fact. It has to be part of the original solution.
Next, question – assuming that the product has RAID, what is the user experience? Does mom have to quiesce the array, identify the failed drive, replace that drive (after it’s assembled into the drive canister), and then launch the GUI to start a rebuild? BTW, what should the rebuild rate be? Is “3” a good number? And what the heck is “3” anyway?
I’ll go out on a limb here, but that’s probably not how it should work. In fact, if at any time your mom saw the word “RAID”, then you got it wrong. And I doubt she even needs to know that a drive failed. She just needs to know that a “thing” needs to be added or replaced. It’s like the memory card in her digital camera. When the time comes to do something, error message #47 doesn’t show up on the display. Instead she sees a message such as “thing full” or “insert thing A into slot B”. And it better be real clear where you buy thing A – like memory cards.
Note that where the RAID happens doesn’t really matter. It could be in a traditional HW RAID solution or it could be in software RAID. But it doesn’t have to even be inside the box that contains the “replaceable things”. Some folks like Zetera are putting drives on the network and then using host software and routers to perform the RAID. It’s all good.
So how this will all roll out over the next few years isn’t entirely clear. But somehow someone will figure out how to make your home data safe, and the methods will be varied, and some methods will succeed while others flop.
Only one thing is certain: Don’t call it RAID!
TT
November 1st, 2006 at 6:39 am
Perhaps you can assist on this point. I have purchased from an auction 2 ultra320 scsi drives. Can I purchase a suitable Adaptec solution (PCI card) and will it support 2 drives, i.e., cables from the drives to the card? Or do I need an enclosure to house the drives then connect by means of a totally different cable, i.e., from enclosure to card?
November 2nd, 2006 at 11:48 am
Hi,
I’ve got at home a small NAS solution from Linksys (NSLU2). I started with one USB drive connected on it then i realised that all my pictures, movies, banking informations were stored with any HW redundancy so i decided to install a second USB drive. The NSLU2 is able to copy every day the whole content of Disk1 to Disk2. It’s clearly not a RAID 1 but at least it provides a security if i loose a drive.
The solution cost was around 300$ for 300GB of disks.
Cedric
November 3rd, 2006 at 10:09 am
Cedric, yeah, I’ve had my eye on that Linksys box for my own home use. Looks like a good product. I didn’t realize that it could automatically copy data. Very nice.
But I heard that performance was horrible, and that the USB drive could not be moved back to a normal Windows machine and be read. What do you think about that?
TT
November 3rd, 2006 at 10:11 am
Anonymous, it’s easiest if you have room in your computer case to mount those drive. Then you can use a cheap internal SCSI cable. If you go external you’ll have to buy a different and more expensive cable. Plus, you’d have to by an external box with integrated power. That’s probably going to cost you $100-200 more than just staying internal.
Also, if decide to go external, make sure your SCSI card has an external connector.
TT
December 2nd, 2006 at 10:56 am
Hi,
Personally, I use the home “NAS” solution from Linksys. It is really a good product, for a very nice price. It can do batch copy of data from DISK1 to DISK2 and also could be used as an incremental backup device if needed. I bought it to provide centrlized acces to multimedia files from all computers in my home. Cerneanly, performance is poor, compared to IDE HDD but it is quite good.
Before this device I have tested a box from Netgear (SC101). Nice design but … that’s all. Hangs while transferring large files and uses a driver which should be installed on the system (Widows only). Sold the same price as the Linksys device, it does not provide network storage solution.
Conclusion: Linksys is the product to chose if you need home network storage with buit-in security and data backup facility. It’s not a real-time mirroring (RAID 1) but secure enough for home usage.
I still have one question: What does it happend if I swap the 2 HDD ? Data still readable ? Hope so …
Chris (Paris/France)
December 4th, 2006 at 11:20 am
Chris, I’ve looked at that Linksys box also. I read somewhere that once you put the data on a USB drive behind the Linksys box, then you can’t move the USB drive to a normal computer and access your data. Do you know if that’s true? I’d hate to be tied into Linksys forever.
As far as swapping the HDDs: Yes, a hardware RAID card should be able to put the RAID together during boot regardless of which port or address the drives are located at. But I wouldn’t try it during normal operation.
TT