Need Help with Raid-1 ( Data Mirroring )

Discussion in 'Data Sets and Feeds' started by kevinqc, Dec 17, 2010.

  1. kevinqc



    I am ordering a new Dell system with Raid-1 but not sure of Raid-1's pros & cons.

    The main reason is data security. But few questions.

    (1) Currently I clone my HDD twice a week as a back up using Acronis True Image software. Could I still do that by removing one of the Raid 1 drive OR the Raid -1 configuration will duplicate the new 3rd drive when I remove the 2nd drive ?

    (2) Could I remove the Raid -1 configuration in case if I don't like it for any reasons ? In that case could I continue on cloning the drive as I am doing currently using Acronis ?

    (3) Any other pros or cons ?

    Thank You.
  2. I use RAID 1

    Having a 3rd HDD and swapping out one HDD periodically works well. In the event of even slightly predictable disaster (wildfire, hurricane, flood) you can grab the 3rd HDD and run out the door. You can keep it in a small firesafe box. And if it has valuable data, in a small firesafe box in a vault.

    I can't imagine you would not like it, but I don't know you or your setup/ operations. If you don't like it, it's no problem to remove the array at any time and go back to Acronis.
  3. After our company had a major outage caused be a single harddrive failure on a desktop system. Our servers are all hardware RAID-1 or RAID-5.

    After about a year, I quietly gave up on RAID-1. The problem is that Windows/drivers crap out too often. Without a hardware cache, every hard reboot means a consistency failure. Not that one driver is really much better than the other in such cases, but consistency must be reestablished ASAP. Windows can rebuild the RAID in normal mode, but your apps are understandably when the disk is running at 100% for hours.

    Hardware RAID with separate battery is another story. Our servers sailed through several harddrive failures.

    For the BIOS on my Dell Desktop, Dell Server, and ASUS computers, changing from RAID-1 to non-RAID, meant reformatting the drive and reactivating Windows.

    We considered using RAID as a way to create offline mirrors, but honestly, the Microsoft tools (robocopy and restore disks) does a much better job.
  4. kevinqc


    Hi mgookin,

    First how would I transfer my existing data to new Raid-1 system ?

    I am ordering 500 GB Raid-1 & my old data is also on 500 GB HDD. So do I just replace the new Raid drive 1 say with old HDD ?

    I have critical data which keeps on changing every hour & thus I need a continuous back up as well as a drive ready to be replaced in case of a HDD Failure. I am using windows 7.

    Steven, what does it mean when you say hardware Raid with a separate battery ? Motherboard has one battery that I know but are you saying there must be another battery just for Raid Card ?

    What kind of a hardware you need for a Raid configuration ? A Raid hardware card ? Plus a Raid software ?

    mgookin, Can you please address some of the problems listed by Steven.Davis because this is totally new to me & only people with actual use of it can address the issues in great details.

    I am asking Just your opinions & in no way to criticize steven or anyone else.

    Thank You both.
  5. Steven: I think you're talking about a RAID on the OS drive. We're talking about RAID on data storage drives. It's the data being protected. The drive can be plugged into any pc, laptop, etc. and instantly accessed. That's what's great about it.
  6. There is no "RAID card" and there's "no batteries required". Modern MOBO's have built-in RAID support.

    With respect to xfer of data from old drive to new drive, that's a simple plug & copy. Win7 has an integrated means to do it but I've never used theirs.

    The size of your RAID will only be as large as the smallest drive. While not required, I strongly urge all drives to be identical with respect to brand, model number and size. If you want a 2 disc array and you're going to swap a 3rd in and out, but that 3rd HDD at the same time from the same place. Tell Dell you want a 3rd drive. They'll put it in the machine as a stand alone drive. Just remove it from there and let it sit on the shelf as your 3rd drive, then swap it on the schedule you're swapping on.

    I don't know what flavor of Win7 you're getting, but look on Microsoft's website and see if it offers shadows. I use shadows and I'm on Win7 ultimate x64. This way you not only have your dynamic clone but you can go back in time to previous versions. For example, if at noon you have a problem, you can simply go back to how those discs existed at 10am.
  7. What kind of Dell did you buy?

    You might want to check out RAID5 with 3-4 HDD.

    OP, when you boot up your machine you will need to go into the BIOS (Press F2 during boot just after the Dell screen), enable RAID/Auto and then just after the Dell post press Ctrl+I to access the Raid menu.

    Its pretty easy.
  8. I believe the OS will take care of that through Disc Management.

    There's been a transition in the past few years to allow the OS to control what previously was controlled by the BIOS things like fan speeds, disc management, etc.

    In Win7 it's Control Panel/ System & Security/ Admin Tools/ Computer Management/ Disc Management
  9. RAID/Backups/journaling file systems/live database backups/versioning - this is a big area

    KevinQC has "critical data which keeps on changing every hour & thus I need a continuous back up as well as a drive ready to be replaced in case of a HDD Failure."

    I don't know if this is transactional data which needs a database replication/clustering solution. For example, if a customer pays for a service and the primary database machine blue screens, the customer still need to be authenticated for a hot-standby/cluster database server. Data is not recoverable, realistically so no data loss is acceptable. Solutions to this kind of problem tend to be very database specific.

    Perhaps, the data is market data, like trades and quotes. Then you not only need to preserve the "history" you have, but you also need a way to fill the gap. Often this means that a little data loss is ok, just more to fill.

    Modern motherboards have built-in RAID which is really implemented by the OS. When there are OS/driver issues, this can often cause consistency errors which in turn cause performance problems.

    For desktop machines, Dell or otherwise, I have abandoned RAID. Whether for the OS or for TBs of market data. Since market data can be gap-filled, I have found it to be far easier to install a bunch of disks and use robocopy/Windows Backup to make regular backups to secondary drives. This insures a clean copy (if master fails, have backup, if backup fails, copy over again.) By connecting the backup drive using a USB docking station, I can cycle through a set of backup drives. No need for them to all be identical, and I can always carry one over to another system if I need something too big for LAN speed.

    RAID is great at improving uptime on servers (no flaky drivers need apply.)

    Dell servers have typically use a PERC controller card which has its own memory stick and battery. This way, the OS thinks that it has either written some data or not, and the data will get really written when the drive have enough power to do it. I did demote a production server (RAIDed) to a test server (no RAID,) and I didn't see how to unRAID the RAID-1 drive without reformatting it.

    People doing serious databases often uses a separate chasis such as a Dell PowerVault to house the drives and handle RAID issues. There are lots of cool things that can be done this way.

    Since people are moving to blade computers, a SAN (like a separate file server in your LAN connected by a fiber channel) is getting to be a popular option. Again this is a cool topic with lots of cool things that people are doing.

    Back-ups. Mirrored, logged, transported, cycled, versioning, ... Lots of good stuff.

    Don't really know what you needs are.

    I agree with MGookin that having matching drives is important. Ordering a third-drive and configuring it as a hot-spare is a good practice. In my experience with Dell/PERC-5, the hot-spare does not kick-in automatically. I had to do it in the PERC BIOS. It is possible that I could have done it live with Open Manage, but I didn't try.

    I also agree that Windows 7 shadowing to be invaluable. (Journaled File Systems in general.) There are, however, pros and cons for certain applications. Databases can be helped or hurt depening upon configuration. Market Data really doesn't need it, and depending upon your purposes, contiguous data may be valuable.

    Anyways, it is a big subject inwhich alot of smart people are earning innovating.

    Hope you find the right balance.
  10. OP did you get it sorted?

    Your dell should have RAID built into the motherboard. Back up to an external HDD, build your RAID1 on your 2x 500gb hdd and then move the data back onto your system.
    #10     Dec 19, 2010