RAID 0 + 1 mirror drive

[Shroom]

So I've been thinking on how I want to set up the hard drives in my main PC, and I have a little question about how to work out the RAID.

Once I build a NAS and transfer the data off of my 4 x 1TB WD Black RAID5 array, I want to re-purpose some of those hard drives for local storage for my main PC. I'm thinking I would like to put 2 of the 1TB Blacks in RAID 0 just for storing locally cached media and Steam games.

What got me thinking was that backing all this up over the network to my NAS would be pretty painstaking and bandwidth-killing to do regularly, so I had another thought. Is it possible to use a third 2TB HDD as a perfect mirror for the RAID 0 array? I.e to mirror the (2 x 1TB WD Blacks) 2TB RAID 0 onto a 2TB Caviar Green. I know this is possible in FreeNAS but is this a common practice that most integrated solutions could support (i.e. X58 or Z87). If not, I have a RocketRAID 2310 card I could use but would prefer not to as it is limited to SATA II and adds about 30 seconds to my boot time (and no SMART functionality I believe).

Not really sure if this is forum is even the proper place for this question as it doesn't exactly have to do with FreeNAS but I figure there's a lot of RAID buffs here who might have an answer for me.

 

[Nick2253]

First off, RAID is not backup. If you really want backup, don't use RAID.

If you are doing incremental backups, I doubt you'd have much bandwidth issues after your first backup. After all, a gigabit network is capable of moving approximately 100 MBps of data, which would allow you to do a complete backup of your 2TB array in under 6 hours (obviously you won't get sustained speeds quite this fast, but I think it's unlikely you actually have a full 2TB worth of data).

I would strongly recommend against using integrated RAID, because it's basically the worst of both software and hardware RAIDs. Your RocketRAID card will give you more bandwidth, and none of your disks will benefit from SATA III. I'm not sure if the RocketRAID card would be able to create a three-drive RAID 0+1, but I would think you could.

 

[cyberjock]

X58 and Z87 are not "integrated solutions". They are chipsets for a particular system, nothing more.

 

[Shroom]

First off, RAID is not backup. If you really want backup, don't use RAID.

If you are doing incremental backups, I doubt you'd have much bandwidth issues after your first backup. After all, a gigabit network is capable of moving approximately 100 MBps of data, which would allow you to do a complete backup of your 2TB array in under 6 hours (obviously you won't get sustained speeds quite this fast, but I think it's unlikely you actually have a full 2TB worth of data).

I would strongly recommend against using integrated RAID, because it's basically the worst of both software and hardware RAIDs. Your RocketRAID card will give you more bandwidth, and none of your disks will benefit from SATA III. I'm not sure if the RocketRAID card would be able to create a three-drive RAID 0+1, but I would think you could.

First of all the RAID 0 is not for backup, just for speedy local storage. I want it to be backed up with some method that is cheap, easy, and efficient, such as a 2TB WD Green that does nothing but backup the RAID storage and is not likely to fail for some time, and even if it does, it's unlikely that the RAID will fail before I replace it, or that the RAID and the secondary drive will experience issues simultaneously.

Secondly, 6 hours for backing up my PC is way longer than I want it to take. 2 hours is what I expect it to take to back up less than 2TB worth of data (the RAID 0 plus the OS drive) using Windows Backup through SATA to a local drive, especially if it must be done nightly. The local drive can be backed up to the NAS server monthly or weekly as a secondary measure.

Alternatively, I'd prefer to have the second drive somehow just mirror the RAID 0 setup, but I'm still not sure this is possible outside of FreeNAS. I definitely am not using the RocketRAID controller again. It works well enough but is hardly robust enough to be worth dealing with. It also slows down my otherwise speedy boot time which is a huge pain. I plan to be upgrading to a 1150 board and a 4770k soon after building a NAS, so I'm not too worried with how the onboard RAID feature will perform with only 2 or 3 harddrives.

 

[Shroom]

So, is there any way to have some sort of striped RAID setup with 2 performance (WD Black) drives, and a third disk (possibly a different series, such as a WD Green or Red) for parity?

Could RAID 4 do it?

 

[Nick2253]

Obviously RAID0 is not backup. But you're talking about using a mirror (RAID1) of that striped (RAID0) array as backup. That is not backup.

If you do incremental backups, you'd only have to do the full backup once. Then, all you'd have to transmit is the incremental data. If you're not doing incremental backups, then I'd strongly suggest you rethink your backup strategy.

The problem with onboard, or integrated RAID solutions isn't just the performance. You're also often stuck without any kind of proper redundancy. Many of these so-called RAIDs are incapable of surviving a failed drive, and if you ever have to move the drives off of the computer, good luck getting it to work somewhere else. You get exactly the same performance, without any of the proprietary stuff, by using the software RAID in Windows.

RAID works best with identical (or near identical) disks. If you do like you said, your performance disks would be worthless, because they'd constantly be waiting for the parity disk to catch up. A RAID array performs as well as its weakest member. RAID4 has nothing to do with your solution. It's simply the older (and less performing) version of the already outdated RAID5.

 

[Shroom]

Obviously RAID0 is not backup. But you're talking about using a mirror (RAID1) of that striped (RAID0) array as backup. That is not backup.

If you do incremental backups, you'd only have to do the full backup once. Then, all you'd have to transmit is the incremental data. If you're not doing incremental backups, then I'd strongly suggest you rethink your backup strategy.

The problem with onboard, or integrated RAID solutions isn't just the performance. You're also often stuck without any kind of proper redundancy. Many of these so-called RAIDs are incapable of surviving a failed drive, and if you ever have to move the drives off of the computer, good luck getting it to work somewhere else. You get exactly the same performance, without any of the proprietary stuff, by using the software RAID in Windows.

RAID works best with identical (or near identical) disks. If you do like you said, your performance disks would be worthless, because they'd constantly be waiting for the parity disk to catch up. A RAID array performs as well as its weakest member. RAID4 has nothing to do with your solution. It's simply the older (and less performing) version of the already outdated RAID5.

Perhaps a mirror of the RAID0 array isn't the most efficient solution, and I only suggested RAID 4 because the parity was all on one drive which would be all I need, but I guess if the parity drive is going to limit the rest of the array it wouldn't be worthwhile. I don't need a very robust local backup since external backups will be handled separately and the local backup is just for convenience, not true redundancy or reliability.

But I suppose even a local drive just to handle backups is probably unnecessary if I do external backups incrementally, I just didn't want to be saturating my router every night just for backups. Thanks for the input.

 

[Nick2253]

An incremental backup solution, especially if thought out to correspond to how you're changing your data, can take up almost no network bandwidth. One one computer system in my home, which I use for video editing, I create a ton of changed data. But because I do incremental backups every three hours, I see no network latency, because I'm not actually changing that much data each time I do the incremental, and even if the backup comes on while I'm working, it doesn't really add that much overhead because of resource limits I've set on the backup task.

 

[Shroom]

An incremental backup solution, especially if thought out to correspond to how you're changing your data, can take up almost no network bandwidth. One one computer system in my home, which I use for video editing, I create a ton of changed data. But because I do incremental backups every three hours, I see no network latency, because I'm not actually changing that much data each time I do the incremental, and even if the backup comes on while I'm working, it doesn't really add that much overhead because of resource limits I've set on the backup task.

Good point.

What program do you use for your backups?

 

[Nick2253]

Acronis True Image for my Windows Machines.

 

[cyberjock]

2TB of data.. over saturated Gb LAN nonstop(which is totally impossible unless you are straight SSD on your Windows box), doing 1GB every 10 seconds would only do about 720GB/hour. So 3 hours is the absolute best you could *ever* hope for. Since you probably aren't doing straight SSD, I don't consider 6 hours to be unreasonable in the slightest.

Sorry, but what you are expecting is just unrealistic.

 

[Shroom]

2TB of data.. over saturated Gb LAN nonstop(which is totally impossible unless you are straight SSD on your Windows box), doing 1GB every 10 seconds would only do about 720GB/hour. So 3 hours is the absolute best you could *ever* hope for. Since you probably aren't doing straight SSD, I don't consider 6 hours to be unreasonable in the slightest.

Sorry, but what you are expecting is just unrealistic.

I wasn't expecting less than 6 hours for over 2TB of data transfer, I was expecting less than half that for a full daily backup of my main system, by whatever method. I want to keep daily backups under 3 hours, but at this point I don't think I'll have any time issues doing backups incrementally since there aren't going to be huge changes on a daily basis.

 

[cyberjock]

Actually, you may not see any benefit with small daily backups. Some backup programs do a complete decompress of the backups its using for determining incremental/differential backups. So you may still see absurdly long backups. Still others let you toggle this setting.

 

[Nick2253]

Actually, you may not see any benefit with small daily backups. Some backup programs do a complete decompress of the backups its using for determining incremental/differential backups. So you may still see absurdly long backups. Still others let you toggle this setting.

I personally don't have this problem with Acronis, though other's miles may vary.

 

[cyberjock]

Yeah, i can't vouch for Acronis anymore. They were pretty good(I used and recommended them for years) but they took a leap off the cliff in the QA department around 2010 or so. I bought it and I couldn't backup any of my desktops. They didn't want to give me a refund, so I left them and never looked back. I wasn't alone with the problems with backing up over network shares either. It was their most common complaint in 2010..... and 2011... and 2012. I figured if they could fix a common error situation in 3 damn releases/years they can eat a pile of sh*t. I haven't looked at them since 2012 and since O&O works just fine(and is cheaper) I've never looked back.