RAID Trust Issues — Windows Or a Cheap Controller? 564
NicApicella writes "My new system has two sparklin' SATA drives which I would like to mirror. After having been burned by a not-so-cheap, dedicated RAID controller, I have been pointed to software RAID solutions. I now stand in front of two choices for setting up my RAID: a Windows 7 RC software RAID or a hardware RAID done by the cheap integrated RAID controller of my motherboard. Based on past experiences, I have decided that only my data is worth saving — that's why the RAID should mirror two disks (FAT32) that are not the boot disk (i.e. do not contain an OS or any fancy stuff). Of course, such a setup should secure my data; should a drive crash, I want the system up and running in no time. Even more importantly, I want any drive and its data to be as safe and portable as possible (that's the reason for choosing FAT32), even if the OS or the controller screw up big time. So, which should I choose? Who should I trust more, Microsoft's Windows 7 or possibly the cheapest RAID controller on the market? Are there other cheap solutions?"
Are we talking Pr0n or Tax Receipts here? (Score:3, Interesting)
As for Motherboard RAID chipsets... Keep in mind that your motherboard has a non-zero probability of frying, having it's caps go bad, being peed on by irate government agents, etc.. I once had a RAID 0 array that was hooked up to one of those things. After the Mobo died I had to do without letters K through P of my Japanese horror-comedy-porno-game-show collection until I was able to find a used computer with the same RAID chipset. (I don't know if it's changed, but at the time each different RAID chipset made RAID 0 arrays that were not compatible with anything else on this lump of rock.) If data portability rather than performance is a priority for you, my advice would be to avoid hardware RAID entirely.
Re:Real RAID is cheap (Score:5, Interesting)
Wrong. You need to buy at least two of these controllers, at the same time, or else when your "real" RAID card dies (and they do), you'll lose all your data unless you can find an identical card (you may even need the exact same firmware version).
Software RAID on Linux is a much better solution, as the underlying hardware doesn't matter. You can mix and match different drive models/sizes (can't do that on HW RAID), and swap the drives to a different system and still read them thanks to the standardized on-disk data format.
Re:You are asking the wrong question. (Score:5, Interesting)
Ive had #4 happen to me. A power supply in my computer failed (a name brand one, not a cheap no name brand) and damaged everything attached to one of the 12v rails. This included both drives of a raid1 set. (ironically all my drives that wernt part of a raid set were completely undamaged) I was later able to recover the data from both drives (both had damaged sections but different areas were damaged on the 2 drives allowing for a complete recovery between the 2 of them)however it goes to show that just having a raid array wont completely protect you from hardware failures.
Re:Are you crazy? (Score:3, Interesting)
A periodic rsync copy (with history) is much better for keeping your data, accidental deletion or overwritten partition tables happen very easily, no RIAD system will save your 'ass'.
Preferable you keep the copy on an other machine, different UPS or surge protector and not in the same machine, hanging on the same PSU. Even better is to copy it to a remote place.
With current bandwidth 'limits', it's possible a good idea to keep it somewhere else.
There's some truth to that... (Score:2, Interesting)
We're talking about an environment that has more then TWO MILLION VIRUSES in the wild, and if your choice of Window-hardening software doesn't stop every one of them, you're screwed anyway, headed for a flush and fill. (And potenitally paying another $100). Welcome to Windows.
Sure, it's been a LONG time since Stacker, the 'wonderful new idea to double drive space', but since it was in Windows, it would last about a week before some memory-hogging virus or poorly-written program would stomp on it.
Hardware RAID can be a disaster; I got in a place and time where corporate data was on a set of drives, there was a failure, and the OS maker decided NOT to make a driver for the replacement RAID card we had. (at great cost and by FedEx!) I had to downgrade the OS, load the data to another device, upgrade it and throw away the raid entirely. What a bitch!
It's even part of the reason I delayed using software RAID on Linux- I was gunshy.
But I tried it. You'd expect the extra overhead to cost access-time, instead it speeds up reads! And the writes (at least in Linux) happen in the background so you don't notice any lag. I've run software RAID in Linux for YEARS, replacing drives and adding spares, etc. It's solid. Not only solid, but (for small applications) the best thing out there.
(If you're gonna approach Amazon.com, hardware RAID, all the way!)
Across the distributions, Redhat's got the lead in RAID-at-install-time, but every Linux out there has the ability. It's worth a shot!
Re:Just remember the first rule of RAID 0 (Score:2, Interesting)
Do you have any evidence for this claim?
There is no need to go throguh the extra effort to use the same model of disks throughout an array or even keep a spare solely so you can have the same model in the event of a failure.
Cheep Non-RAID Controller! (Score:5, Interesting)
Fast facts:
I prefer pure software RAIDs, for a simple reason: They do not depend on available hardware. If one controller dies, switch to another one: Other brand, other type, other drivers, and the RAID still works. If you insist, you can even mix an IDE drive, a USB drive, a SATA drive and a SCSI drive into a single RAID. Try that with a hardware or host RAID. Some people even built RAIDs of floppy disks or USB sticks (not for pemanent use, of course).
My faithful old Linux home server runs two RAIDs, both in software: a RAID-1 for the OS (remember: the BIOS does not know about the RAID), and a RAID-5 for the data. The RAID-1 used to run on old SCA drives, but recently, I switched to two small IDE drives due to unrecoverable SCA cabling problems. The RAID-5 is composed of four IDE drives, connected to two IDE controllers, each disk on a single IDE cable. An external USB disk is used to back up my data, rotating through 10 days. All filesystems are ext3, all disks are monitored using SMART, all RAIDs are monitored. If anything wents wrong, I will get an e-mail from the monitoring software.
Until recently, one of the controllers was an el-cheapo non-RAID controller, and the other one was a donated, expensive, well-known brand, RAID-capable controller running in non-RAID mode. The latter one decided to randomly take some free time on the job, and either disconnected from the PCI bus or disturbed it, causing panics in the OS above. Only pure luck protected me from data loss. I ripped it out of the machine, kicked it into the trash bin, rewired the RAID to use two disks per IDE cable, and verified and reconstructed my data. Some days later, another el-cheapo non-RAID IDE controller arrived, the same brand, model and type that already sat in the next PCI slot. So I rewired the RAID again to work with one disk per cable, everything was fine again.
For a new small business or home server, I would use nearly the same setup again: Two software RAIDs, one for the OS, and one for the data. Upgrading the OS is just fun when you can
Re:You are asking the wrong question. (Score:3, Interesting)
I learned this important lesson when setting up a RAID array for audio and video production. It increased my throughput tremendously. When you need to stream digital video or audio into an editor, or a multitrack recorder, It really helps to have more than one disk doing it. Of course, I can't use FAT32 like the author because I often have very large files to move around.
However, RAID on my regular desktop has never been much more than a headache. Now I just make sure I have a good backup system in place. I am surprised at how many new desktop systems come with RAID enabled by default, especially since Vista and SATA came along.
Re:Just remember the first rule of RAID 0 (Score:3, Interesting)
You may have noticed that some hard drives are marketed as being designed for RAID use. These work slightly differently to most consumer disks. Typically, a small region of a disk is hidden. If the disk discovers a bad sector then it will use one from the hidden region to replace it, so every write to the bad sector goes to one of the spare ones instead. This is very bad for RAID, because two drives writing to the same sector may be writing to two different physical locations (if one is remapped), with the same problems I outlined above.
Disks designed for RAID use do not have this behaviour. If they find a bad sector, they report this to the OS. The RAID controller will then mark that sector, and the corresponding sectors on the other disks, as bad and not use it in future. Note that there is no performance gain from using RAID disks in a single-disk configuration, although this doesn't stop some people trying...
Re:FAT??? (Score:3, Interesting)
I've messed with software RAID in Windows 2003 server for years and have never had a drive failure not reported to the Event Log.
Well, sure, but how often do you read your event log? Most users _never_ read their event log, so logging the failure like this is next to useless. This is something the user needs to know about, immediately. At the very least a notification area icon and pop-out box would be appropriate.
Re:You are asking the wrong question. (Score:5, Interesting)
That's an interesting thing... the power supply has more potential to cause damage than anything else in the PC, but nobody ever thinks about protecting against its failure. Makes me wonder why we don't have surge protectors on the 5/12V rails as standard yet.
Re:Are you crazy? (Score:5, Interesting)
I'm still somewhat astonished that WD would think that it's acceptable to have external drives that work on OSes other than Win except for the power management features. Saying you're just supporting Win for a hard disk is nowhere near acceptable.
Personally, what I do at home is I use ZFS to mirror a pair of 1tb Seagate drives and that seems to work fine, it's not really the best set up, but it's hard to get such things located off site for the amount of money I have to spend.
Re:You are asking the wrong question. (Score:3, Interesting)
Plus, the RAID array can keep track of where the head is on each drive and choose the one that's closest to the requested sector. Linux software RAID does this, though I don't know specifically who else does.
Re:You are asking the wrong question. (Score:3, Interesting)
Try areca raid cards, they do give a performance boost on raid 1, but of course a slight performance hit on writes.
Can't have everything.
Re:Just remember the first rule of RAID 0 (Score:1, Interesting)
That makes no sense. The recommended setup is to actually use a bunch of disks from different vendors which means they're all going to be slightly different. Tons upon tons of people run with this type of setup with no issues.
Not too long ago a disk in my RAID5 went bad and I replaced it with another drive that's not even close to the same size. I just made a partition that was about the same size as the old drive and mdadm rebuilt the array with no problems. Been running fine.
I think your problems stemmed from you not knowing what the hell you're doing. Not totally your fault because the whole RAID system in Linux is confusing (MD RAID, LVM, etc). I stay away from all that LVM and other crap, just pure kernel MD stuff for me.
Anyway, back to the original question the poster asked. Never ever use a motherboard "hardware" (actually it's software) RAID controller. That's just asking for trouble. A dedicated hardware RAID controller card might be OK but what if the controller itself goes bad? Are you sure you will be able to get to your data? For me, an OS software only solution is the only way to go.
Re:You are asking the wrong question. (Score:5, Interesting)
Heh. Linux software RAID doesn't do jack. I've looked at the source code. The mdadm RAID1 driver just alternates drives for reads whenever the requests are not contiguous. That is all. Nothing more. There's no intelligence in there. No keeping track of head positions, no attempts to discover or infer physical drive geometry. Nothing. Just a simple round-robbin. It just so happens that for MOST things that involve random access, the effective throughput is nearly doubled. More intelligence wouldn't actually buy you much in the general case, so why bother?
Also, the dmraid (fakeraid) RAID1 driver only does reads from one disk. I made the mistake of using dmraid instead of mdraid, only to discover through performance tests and iostat that there are basically two software RAID drivers that CLAIM to do identical things but in fact do not.
Re:You are asking the wrong question. (Score:3, Interesting)
I would expect this - modern drives (when I say modern I mean any drive made in the last 15 years) is effectively a black-box to the computer. The OS has absolutely no idea where the heads are, or even how the sectors are actually laid out on disk. Any attempt to be "clever" in ordering reads is doomed.
Re:Just remember the first rule of RAID 0 (Score:3, Interesting)
Yes, Mod parent up. RAID is for providing data resiliency, not data protection. In corporations where either very large data sets would simply take too LONG to restore, or where spindle count for acheiving IOPS is critical, RAID permits a reduction in failure rate. However, is it NOT a replacement for backups, and RAID should generally only be considdered when you;re already considering a multiple disk setup (either for capacity or performance reasons).
A RAID1 setup on your home computer may increase your uptime, and a RAID 0 can imrpove your performance, but generally, it's not that improtant, and on a home PC, typically the OS drive is more critical than the data drive (It's easy to resorte a backup, It'sdifficult to make your machine exactly as it was if you loose the drive and need to re-install).
That said, even a data backup is NOT enough. You also likely need an image/BareMetal backup of the OS and application drives. Rember, it's one thing to limit hardware failure by using a RAID, and another to have good backups of your data, but you also need to take the human factor into account: 1) your mistakes change both RAID 1 disks, there is not rollback; 2) hackers and viruses corrupt data just as easily on your external USB used for backup as it does on your primary drive, unless you're using top nothch backup software that hides the backup[ device from Windows and makes the backups unreadable to the OS (rare); and 3) software installs, bad code, and Windows itself can just as easily render all your data useless.
If your data is important: ...and NO, there is NO SUCH THING as a surge protector that can stop a lighting strike. The EMP alone is good enough to destroy data. (I've seen a montior and PC 4 feet from the nearest outlet get cooked when the lightnig's EMP backfed the CRT's stores static energy into the motherboard).
1) Backup regularly, and please use a real backup application, not Robocopy or some cheap scripting system... Keep miltiuple incremental backups and use software that manages a proper rotation and can search offline data to find files you want to recover.
2) Make image/BareMetal backups of the OS. Vista Business and higher editions have something similar built in, but using a program like Ghost is often easier and quicker to restore from. Make a new image at least as often as you install make major changes to your system, or every few patch rotations.
3) DO NOT leave your primary backup device connected 24x7 unless it's a tape drive or worm device. Your backups are easy fodder for hackers on USB drives. Also, a lightning strike or surge that takes out your primary AND backup is bad, really bad...
4) GET YOUR DATA OFFSITE. Fire or water damage should not be able to take out your "important enough to back up" data. This not only includes your backupos, but critical media, CD keys, and anything else you'd need to rebuild the computer far enough to reconnect to your backup disks...
5) Keep this rule in mind: "Nothing is backed up until it's been restored." Well enough that you're doing backups, but if you have never tried to restore your system, you have NO IDEA what that takes, and NO IDEA what you're missing to do it. Done a firmware patch? many of the original drivers may not work anymore, you might need new ones on CD to reload the OS... Maybe you'll find your backup software doesn't have an open file manager, and your e-mail isn't being backed up properly when it's running... Do you have the backup software stored offsite with your backups???
I have nearly 20 years of important files spread across my 3 main computers (including the wife's machine too) totaling about 1.1TB of actual data and files. My main machine runs a RAID 1/0 (mirrored stripes) with 4x 250GB 7200RPM drives on an AMCC/3ware controller (Soft raids SUCK, onboard RAID is not much better, NEVER opt for the lowest bidder if your data and your performance are important...) That's my OS, Application, gaming, and higly-used data drive. I also have a 750
Re:You are asking the wrong question. (Score:3, Interesting)
I'm sitting here laughing at the idea of backing up 1TB when you could just download it all from Pira^H^H^H^H torrent sites again.