RAID 5 Questions

[wrems]

I've never utilized any type of raid before and have a few (noob) questions. I started a thread here about unRAID: http://forums.sagetv.com/forums/showthread.php?t=47749 . I'm still tossing the idea of unRAID around but not sure if I want to purchase a complete new system to run it... That brings me to this thread about using a hardware raid controller in my current server (quad). I've been looking at the rocketraid cards rather than using my mobo (Gigabyte 790x ud4p).

My questions are these: (I apologize in advance of my ignorance of the subject, but I have been unable to find adequate answers online)

1. Are raid arrays transferable?
2. If I upgrade my mobo, re-install windows, or install a different version of windows what happens to the data in my array? Will it be ready and waiting after reinstalling everything?

The main reason I've been considering unraid is the separation of my data in a remote location and far and away from any server related problems. I know I'm probably over thinking it, at the same time, I haven't found my answers. I don't want to have to back up my array just to re-install windows or something. Is this even a concern?

Are there any personal recommendations of raid cards I should be looking into?

[Oats]

If you have a dedicated raid card, you can transfer the card + array to any computer. If you use your motherboard raid it is only tranferable to the same motherboard, sometimes other boards that use the same chipset but not always.

As long as your OS is on a different partition or better yet a different drive then you can re-install the OS without it touching your data.

I have a Dell Perc 5/i raid card that I use for raid5, it was around $100 from ebay. Great price for an 8 port card. Perc 6/i is a little better and a little more expensive.

[stanger89]

Originally Posted by wrems

1. Are raid arrays transferable?

Depends on the definition of "transferable". In addition to what Oats said, "good" RAID controllers (thinking 3ware specifically since that's what I have some experience with) allow/support moving arrays to different controllers/different models even. For example AFAIK even 3ware's latest 9000 series controlers (SAS) can recognize arrays from 7000 controllers (PATA).

What you can't do is go from one manufacturer to another, and sometimes not even from one model to another.

2. If I upgrade my mobo, re-install windows, or install a different version of windows what happens to the data in my array? Will it be ready and waiting after reinstalling everything?

It should be. The array appears as a single large SCSI drive to the OS, just like any other HDD the data is indepenent of OS as long as there are drivers for the controller and the OS understands the filesystem.

The main reason I've been considering unraid is the separation of my data in a remote location and far and away from any server related problems. I know I'm probably over thinking it, at the same time, I haven't found my answers. I don't want to have to back up my array just to re-install windows or something. Is this even a concern?

Not if you pay attention to what you're doing. About the only way you could have a problem is if you were reinstalling windows and told it to format the array instead of the HDD you intended.

Are there any personal recommendations of raid cards I should be looking into?

If you're going to do it, do it right and get something like an LSI/3ware, Areca, or one of the better Adaptec ones. I personally don't trust HPT.

That said, virtualization has come a long way and the idea of running unRAID and Sage on the same server in VMs has caught my interest of late.

[Skirge01]

Everyone is dead on so far. Here are my thoughts from having gone through so many thoughts about RAID, redundancy and backup over the years. Get 2, smaller drives for just your OS. Put those on a RAID1 (mirror) and use a solid backup plan to image your OS drive. This will give you downtime protection via the mirror and a good backup plan for hardware or software failures. Put your other data on a RAID5 (or even RAID6 for dual drive failure protection) and utilize a solid backup plan (duplication) for the critical data.

My biggest issue with RAID is what stanger89 mentions regarding moving from one RAID card to another, plus the fact that most (all?) RAID cards require you to use the same size drives. For the latter, expansion can be problematic. While it should work, you simply aren't guaranteed to be able to do either of these. For this reason, I would utilize something like WHS (for duplication) or FlexRAID (for parity protection) or both. Keep in mind that FlexRAID is not meant for constantly changing data, such as your recording drives. If it's possible, unRAID in a VM sounds fantastic. I wish WHS could run in a VM.

Where I've seen so many people (myself included) go wrong is thinking that RAID = backup. The truth is that RAID = uptime (of the server and, hence, access to most data) and DUPLICATION = backup (on a separate drive on which the data will still be accessible even if the server won't even power up). This is where you completely eliminate the concern with something going wrong during your two questions because you have a backup of the data anyway. If the array goes south, your important data is still safe, accessible, and able to be restored once the server and/or array is working again.

[Oats]

Another thing you need to worry about with RAID is some drives are prone to going into some kind of error correction mode that causes the drives to time out of the raid array. This isn't a problem if you get enterprise class drives, but they are a lot more money.

Originally Posted by Skirge01

I wish WHS could run in a VM.

I'm currently running WHS on VMWare Server without any problems. I had to change the HDD controller from the default to BusLogic and do F6 drivers during installation, but that was the only tweak I had to make.

[Skirge01]

Originally Posted by Oats

I'm currently running WHS on VMWare Server without any problems. I had to change the HDD controller from the default to BusLogic and do F6 drivers during installation, but that was the only tweak I had to make.

Interesting. Are you using the drive extender technology (i.e. drive pool)? Also, are you running SageTV inside the WHS VM, its own VM, or on the host OS?

[wrems]

My goal with any type of raid setup is for long term storage/backup. I want to be able to have some confidence with my dvd rips that I wont have to re-rip them, plus pics and music. Basically, SageTV related stuff sans the active recording.

FlexRAID sounds like it might be a good fit for what I'm looking for. Thanks for sharing that Skirge. I am just now starting to look into that too. I'm keeping my options open about all of this. Far more options than I knew of. UnRaid, FlexRAID, raidRAID, WHS... Probably more that I still don't know about...

[PiX64]

I gotta back up what OATS said

dell Perc 5/i card all the way...hardware raid is the best way to go, most transferable, and will support homogeneous, as well as hetergeneous arrays..

[bsung]

I orginally used the card that came with the Rosewill 8 port enclosure for my data/multimedia. I had my computer die on me and had a great excuse to upgrade so I did and when I reinstalled all the drivers, it worked fine and I didn't lose any data.

I then purchased another Rosewill 8 port enclosure (yes, I know that's a lot of drives). Anyway, when I did, I needed to purchase a single card that had 4 esata ports instead of 2 cards with 2 each. I purchased an HPT card (if you want to know the model, I can get that for you). I can't guarantee that the raid transferred properly because I don't remember but think it did. It's possible I had both cards in and simply copied from one enclosure to the other.

Then, my free upgrade to Windows 7 arrived and after reinstalling a new OS, it still worked. Sometime while using the HPT card and software, I expanded one of my raid 5 with 4 drives into a raid 5 with 8 drives (each same size). It worked fine.

Part of the reason I think this worked is because this was the cheaper software raid option (someone please correct me if HPT is hardware but I didn't think so). Using my raid for mainly Sage files means I didn't need the fastest setup and I never had any problems with recording multiple shows while watching another. I did turn on WD's TLER feature on the drives.

[davephan]

RAID 5 is more risky than RAID 6 or RAID 1 pairs. With RAID 5, if you lose 1 drive, you are still running, but if another drive is lost before the long rebuild is completed, then all your data is gone. RAID 6, you can lose 2 drives and still be running. The RAID controllers that support RAID 6 are all expensive.

I use RAID 1 pairs. It is not as space efficient as RAID 5, but it is safer. I use a on-board RAID. It would probably be safer to use a RAID card. I have an identical system board/CPU/memory that could be used as a spare.

RAID 1 could be used on the OS drive. However, I think it is more important to image the OS drive every day, so you can recover to a recent image, or go back in time any number of days to a point in time when the system was running perfectly (in case you have system problems). After you have imaging setup for your OS drive, then you could consider running the OS on RAID 1.

Your more important files, such as photos and DVD rips should be protected by RAID, plus a independent portable USB hard drive that you can locate offsite.

Dave

[Savage1701]

I've used 3Ware cards for 5+ years now, and I have to agree with the others - a good brand of card is a must (3Ware, Perq, LSI, etc.) and RAID 6 is preferable to RAID 5 even if you have RAID 5 with a hot spare ready to go. RAID 6 has saved my bacon more than once. Also, as others have said, a good brand of card will allow you to move an array created by it to another controller of its brand, even perhaps if those are in whole different generations of cards.

Another thing that is good is to make sure that your card supports drive roaming - let's say you have an 8 port card. The first 6 are dedicated to your RAID 6 array. But then, for one reason or another, you move a drive on, say, port 3 to a formerly unused port, say port 7. A good controller won't care less. It will just reconfigure itself instantly to recognize that that array is now on ports 1,2,4,5,6 & 7. Ports 3 and 8 will then be the open ports.

Also, a better controller will have a good-sized write-back cache with a battery backup option. This cache will allow your controller to keep up with read/write/IO demands. Believe me, if you turn off the cache on a controller you will notice a massive decrease in speed, not just a little bit, especially at the RAID 5 and RAID 6 level, because the controller will go into a "safe" "write-through" mode and not let the drive write anything until the drive tells the controller the last write operation is done.

Also, make sure your power supply can support a large number of drives. I use dual PSU's on my system. Since laptop drives are getting so high in capacity you can consider those as well, but the warnings below about power savings apply to them as well.

Finally, be careful which drives you use with a controller. Many of the "green" drives out there can give controllers fits, because when they go into power save mode they can fool the controller into thinking they dropped out of the array, and render it, at best, temporarily unusable or constantly put it into a rebuild cycle. Some controllers will then mark that drive as "bad" and not even let you put it back into the array, although that varies widely by controller. Some controllers - Areca - allow a spin-down feature called "MAID" where they will spin the drives down and almost sleep them via the controller. That can save a lot of power and is safe for preventing drive drop-out, but you have to make sure the drives will accept those commands and you have to be willing to allow the array time to spin up when a recording begins.

P.S.: I'm not a huge fan of HPT (I'm assuming you mean Highpoint) or Promise. They can have iffy customer service. Just a few thoughts.

[SWKerr]

I have lost data with RAID 5 both at home and at work. If the machine or the RAID card go bad you can loose data. RAID is no substitute for a good backup on anther Drive, Tape or Machine. RAID increase up time but is really not 100% reliable and should not be used as a backup if it is something you can't live without.

I currently use WHS and am pretty happy with it. It is the file server and also host SageTV. It has been pretty stable overall. The one negative is getting a backup of the OS drive. You really need to reinstall the OS on a new drive and let it rebuild the drive pool. I did this when I went from my trial to the full version and it works fine but you still need to reinstall programs like SageTV and reconfigure some setting. You really need to make sure the SageTV config files are backed up on something other than the OS drive as well.

I was looking at unRAID a little but I can't see where it is getting me anything over what I get with WHS. (Would like hear about it if there is one) If I used unRAID I would then have two machines that need to be on 24/7.

I have to admit after loosing data with RAID I like being able to take my drives out of the WHS and being able to read them in any machine if necessary. Even a RAID1 mirror required a similar\duplicate card. As I understand it unRAID also does this so in my mind a big plus for personal use.

I started out using WHS for with duplicate on but have since stopped using it for all but a few shares. What I do now is have a file sync utility that runs nightly and backups the stuff I would miss to separate backup drives that are not in the storage pool. This would make recovery or moving to a new platform easier. The only negative is I might loose anything that is created between the sync schedule but I really don't change the Movies, Music, Software and Pictures Libraries often enough to worry about it. If I do I run it manually. I have another external drive I use to backup the really important stuff and store it in a separate location. (Fire Insurance)

With my current backup strategy I am considering using a real Windows or Linux server in the future. This would be mainly for RAID 0\10. You cant beat RAID 0 for performance. You increase you odds for failure but it is fast. With a good offline backup I think it would be worth it. I am wondering how big a difference this would make in my SageTV Client machines. I probably will not try it unless the next version of WHS does not come out with some more compelling features. Really performance on WHS with basic SATA hard drives is adequate. It would be nice if RAID 0 would eliminate the dreaded circle and make skipping through a big Blu-Ray rip instantaneously but I can live with it the way it is. I would like to try Linux as a Sage server as well but without a trial version I probably won't do it.

[panteragstk]

I have a related question.

I'm going back and forth between running single drives on a temporary basis before I can buy a "real" raid card.

I'd like to run RAID6, but the prices of large enterprise drives (or even non-green drives) and cards that support level 6 are fairly high. I'd have to save up for a bit to get a good amount of storage. The problem is I'm about to build a temporary server from the parts in my client machine plus a new processor and more memory.

My question is: will I be dumb to just get a sata controller card for the time being as I am out of sata ports on my current motherboard, or should I just hold out until I can assemble a "real" server?

[stanger89]

Originally Posted by SWKerr

I was looking at unRAID a little but I can't see where it is getting me anything over what I get with WHS.

The big one IMO is the efficiency. If you want redundancy, WHS eats half (50%) of your space, regardless of the number of drives. unRAID uses parity so you only lose 1/nth of your capacity.

[Skirge01]

Originally Posted by panteragstk

I have a related question.
My question is: will I be dumb to just get a sata controller card for the time being as I am out of sata ports on my current motherboard, or should I just hold out until I can assemble a "real" server?

Ask yourself these questions: What do you hope to get by running RAID6? What data are you trying to protect? Are the risks to that data truly worth the expense?

My guess is that the answer to one of these questions will negate your desire for an expensive RAID setup.

[Oats]

Originally Posted by Skirge01

Interesting. Are you using the drive extender technology (i.e. drive pool)? Also, are you running SageTV inside the WHS VM, its own VM, or on the host OS?

I'm not using the drive pool as I'm using WHS for computer backups only and it is on a raid5 array. I run SageTV on the host OS since there is no good backup for WHS OS drive.

Originally Posted by wrems

My goal with any type of raid setup is for long term storage/backup. I want to be able to have some confidence with my dvd rips that I wont have to re-rip them, plus pics and music. Basically, SageTV related stuff sans the active recording.

FlexRAID sounds like it might be a good fit for what I'm looking for. Thanks for sharing that Skirge. I am just now starting to look into that too. I'm keeping my options open about all of this. Far more options than I knew of. UnRaid, FlexRAID, raidRAID, WHS... Probably more that I still don't know about...

It is hard to make a choice as they all have good/bad things. No one thing is best. I use RAID5 right now for media but I am seriously considering switching to WHS. The cost of my 3 drive raid5 including drives and controller is about the same as if I ran 4 drives in WHS. WHS with duplication would give me the same amount of space as raid5. Plus it is easier to add more drives to WHS since they don't have to be identical and you can use cheaper consumer drives. If you use consumer drives with raid they can easily drop out of the array, causing a long rebuild/consistency check.

Originally Posted by Savage1701

I've used 3Ware cards for 5+ years now, and I have to agree with the others - a good brand of card is a must (3Ware, Perq, LSI, etc.) and RAID 6 is preferable to RAID 5 even if you have RAID 5 with a hot spare ready to go. RAID 6 has saved my bacon more than once. Also, as others have said, a good brand of card will allow you to move an array created by it to another controller of its brand, even perhaps if those are in whole different generations of cards.

Also, a better controller will have a good-sized write-back cache with a battery backup option. This cache will allow your controller to keep up with read/write/IO demands. Believe me, if you turn off the cache on a controller you will notice a massive decrease in speed, not just a little bit, especially at the RAID 5 and RAID 6 level, because the controller will go into a "safe" "write-through" mode and not let the drive write anything until the drive tells the controller the last write operation is done.

I still think the Dell perc controllers are one of the best. They are made by LSI (a big name brand), they have 256mb onboard cache (Perc 5 is upgradable to 512mb), battery backup is available, and for the price you can't get anything better. Nobody else offers all that for $100. The Perc6 includes raid6 and is around $150 but I've seen them as low as $120.

Originally Posted by stanger89

The big one IMO is the efficiency. If you want redundancy, WHS eats half (50%) of your space, regardless of the number of drives. unRAID uses parity so you only lose 1/nth of your capacity.

This really depends on how many drives you plan on having. I think if you only have 3-4 drives then WHS is fine, but once you get beyond that unraid and raid will give you a lot more space for your money.

[Skirge01]

Originally Posted by Oats

I'm not using the drive pool as I'm using WHS for computer backups only and it is on a raid5 array. I run SageTV on the host OS since there is no good backup for WHS OS drive.

That's what I figured. The drive pool is where people have said WHS has issues when running under a VM. Darn.

[wrems]

I have been considering WHS too. I'm still a little ways off on making decisions. I'm still in learning mode I really appreciate everyones input so far. It's helpful having a community willing to share their advice/expertise.

[stanger89]

Originally Posted by Oats

This really depends on how many drives you plan on having. I think if you only have 3-4 drives then WHS is fine, but once you get beyond that unraid and raid will give you a lot more space for your money.

Yeah, 3-4 isn't bad (that's still 6-8 drives total though, which is rather a lot), but I've learned to plan bigger than that.

Another way to look at it is this, say you want to plan for a medium to large sized home server, it's pretty easy and inexpensive to build a server that can handle 8 drives.

If you do that with WHS and you want redundancy, you're limited to about 8TB of capacity (8 2TB drives of which 4 are usable).

If you go with unRAID (in a VM? ) you can have 14TB of space (7 drives usable) in the same chassis.

[Oats]

Originally Posted by Skirge01

That's what I figured. The drive pool is where people have said WHS has issues when running under a VM. Darn.

I've read about it being done using Hyper-V because you can use raw disk mapping on local drives. VMWare doesn't do RDM for local drives. I read you might be able to use VT-d/IOMMU to pass through the Sata Controller though.