Implementing RAID 1 for PC-based system?

[SambaNoodles 0]

Hi.

 

I am planning to install a 16-ch PC-based DVR system. I'm hoping to just install and let it run more-or-less maintenence free for years. Given that Hard-Disk failures are to be expected, I would like to install extra redundant hard drives into a RAID 1 configuration. Whenever, a hard-drive failes, I would like the system to continue run flawlessly as if nothing wrong occured. Of course I should be able to get some indication that a hard-disk did fail, upon which I could just hop-swap out the failed drive with a new working one.

 

I plan to physically seperate the Operating System (WinXP) and applications from the data (video footage) on different drives. In total I think I would like to use 4 hard disks in a RAID 1 configuration

 

My quesiton is, what is the best way to do this? I just want a system that I can setup and leave alone for years if possible. When a hard-disk failure does not happen, I absolutley do NOT want the system to slow down to a grinding halt after a new hard-drive is put it in, as it attempts to rebuild the array. I don't want a solution that requires me to install some special software or drivers...just want something that works on its own.

 

Do I use a PCI RAID controller? I seperate RAID BOX conntected via E-SATA or GIG-E (NAS). Do I need a seperate RAID array for the O/S and a seperate one for the data. What have you guys found the be the most robust, fail-safe solutions to RAID?

 

I'm confused, and I need help.

[dopalgangr 1]

The purpose of RAID is to either make your data access faster, make your data more failure-proof, or both.

 

The entire point of RAID 1 is data redundancy. While yes, RAID 1 does effectively give you half the storage space of the drives used, if one drive dies, your data is still intact on the second drive. Thus, if you have a hard drive die, it's not so big of a deal. You can just replace the dead drive, and go on with whatever you were doing. This scenario however effectively cuts your storage in half and if you are using 4 drives you will only get the benefit of storage from two of them.

 

RAId 0 gives you more storage space and speed however no redundancy. So if you lose a drive you lose ALL the data.

 

There are also more complex RAID options, to give both more speed and redundancy. My personal favorite is RAID 5, which uses one drive for redundancy, so out of a four-disk array, you get the storage space of three of the four disks. However if you lose more than one disk you will lose all of your data. This is uncommon as you would have replaced the bad disk (hopefully) before you lost another. You can also set these up with "hot spares" this would be a 5th disk that would not be used until one fails. The raid would immediately rebuild using the hot spare and when you replace the bad drive that replacement would become the spare. This raid setup is the best for protection of data and getting the most out of your storage. You can still use the storage while the RAID is being rebuilt.

 

As for the raid cards I only use 3ware cards (generally Escalade models) but they are very expensive. I have had some luck with Rosewell and others. If this is not a totally custom system and maybe a Dell with your DVR cards in it, then just order it with the Dell PERC raid from the factory and go from there. Hope I helped ya.

Edited October 9, 2009 by Guest

[Soundy 1]

If you're going with that many drives, why not just go RAID5? With RAID1, you still have to shut down the machine to swap the failed drive.

 

Here's what I'd suggest:

 

Get a small RAID5 drive enclosure with four drives, like something from QNAP or Synology, and iSCSI interface (be sure it supports this). Load it with drives and configure as RAID5. Be sure to use one with hot-swappable drive bays (some don't have this; defeats half the point of RAID5). Generally, these will beep madly and can usually email you if a drive fails; RAID5 will then allow you to hot-swap the bad drive without ever shutting things down, and will rebuild its array seamlessly.

 

Then use a single small (40-80GB) drive for your system drive and if your software supports it, a separate partition for a "backup" data drive in case the NAS is offline temporarily. Once your build is complete, use an imaging program like DriveImage, Acronis, or Paragon, to create an image of your system partition on the backup partition, then copy that onto a DVD-R (Paragon, at least, supports imaging direct to optical disc).

 

Now, if a data drive dies, you can hot-swap it with no downtime and no data loss... if your system drive fails, it's relatively easy to drop a new one in and restore your image.

 

Mirroring system drives can be done, but it can be a major pain if there's any other kind of failure - say, of the motherboard itself, or the disk controller. It's usually less hassle to simply have that backup image.

[dopalgangr 1]

Good points Soundy!! I prefer the WiebeTech with E-Sata connection. All you do here is through in a ESATA card and connect it to the unit. It does all the raid for you and is hot swappable so you dont have to shut down the system to switch out a drive. Also by using ESATA you get the benifit of a 3GB connection to the storage

 

EDIT- My bad Drobo make enclosures but only up to Firewire 800 no ESATA yet

Edited October 9, 2009 by Guest

[Soundy 1]

Good points Soundy!! I prefer the Drobo with E-Sata connection. All you do here is through in a ESATA card and connect it to the unit. It does all the raid for you and is hot swappable so you dont have to shut down the system to switch out a drive. Also by using ESATA you get teh benifit of a 3GB connection to the storage

 

eSATA is good too, but more limited in distance. Great if you can put the array within a foot or two of the DVR. NAS is handy if you want to put your NAS in a different, more secure location.

[SambaNoodles 0]

Thanks for the tips. Its amazing how imformative this forum is.

[Jorel 0]

I use Intel Matrix RAID which lets me do both RAID 0 and 1 on a pair of discs. If you have more drives use RAID 10. Look for a motherboard with the ICHR9 or ICHR10 chipset.

 

A discreet RAID card useful for RAID 5 (for the parity calculations) however read/write performance will still be poor. Also it can support chassis status LEDs for HDDs on a backplane.

[survtech 0]

RAID 5 is a bit slower but the throughput would still be fine for most applications, especially if the RAID system has its own controller. It still has a few other limitations, though. The primary one is that it is not uncommon for RAID systems to lose more than one drive at a time. It's not that two drives fail simultaneously, but that a second drive can have unreadable data which prevents the RAID from rebuilding after one drive fails.

 

Since video recording is primarily write only (very little reading), a drive can become partly or completely unreadable and the RAID subsystem doesn't have any way to know. It's not like computer data that is typically verified after a write. Storage that is recording streaming video doesn't have the time to verify.

[hardwired 0]

It all really depends on how much you want to spend for that peace of mind.

 

The base systems I build have software RAID1 on two 80GB drives, and storage not RAID (JBOD)

 

Up from there, you can go onboard (software) RAID5, with limitations on recovery options compared with a controller card.

 

The upper line systems I built (48TB native capacity, RAID6) used Areca SAS controller cards, battery backed RAM, with three OS drives(RAID1, Hot spare online), and two 16 bay SAS connected enclosures with 1.5TB drives.

 

That setup can expand up to 128 drives.... And it is definitely NOT slow.

 

Also, as Survtech mentioned above, streaming video is not typically verified on write.. but good controller cards allow you to scrub data later.

[VST_Man 1]

ue the arcea cards and they work great. just had a hd failure and it kept right on truckn' (RAID1mirror) only problem is that darn noisy alarm....I know. it's supposed to bep when a drive fails.

 

I've also installed larger RAID with no problems. I like to build them myself using drive bay sata cages so I can remove when I want.

 

The bottomline is is to apply your budget to a tested RAID configuration and go with it. Mirror works fine for personal use and if you go beyond that it's overkill..........

 

I like to combine a RAID with off-site recordings so that a few camera's are recorded on & off site which provides a second level of "safe". You'll need some band width to go out to the WAN and/or you can do it within your LAN. DVR/NVR software has to support IP addressing/recording.