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Adding Different Size Hard Drives to RAID Arrays? Possible?

edited Mar 2009 in Hardware
Hey Im trying to build a media server that will continually grow in size but not nessecarily with the same size HDs. Now I want some sort of redunancy as this will grow in to 2TB + and well if it completley crashes its a giant pain in the ass.

Currently I have 3 x 300gb Seagate drives and was originally going to create a software Linux RAID 5 array thinking I could add HDs. Now I know you can add HDs to RAID 5 but I have no clue how, the other problem is that I probably wont continue to add only 300gb HDs as the larger size ones continue to get cheaper and cheaper but once again RAID 5 is only as good as the smallest HD multiplied by the number of HDs so adding a larger 400gb is a waste of space.

So what should I do? I want some redundacy (Parity information seems to be the cheapest solution), also all the HDs under one drive letter, not 7 or 8, and the ability to add different size HDs later down the road. :confused: :confused: :confused:

Comments

  • EnverexEnverex Worcester, UK Icrontian
    edited Jun 2006
    Adding different size drives works fine, people just don't normally recommend it. On the nVidia array you can use their Windows tool and it lets you add drives to an active array on the fly (or remove them) so I'd look for some tool from the RAID manufacturer or for an option in the post-post controler screen.
  • edited Jun 2006
    Enverex wrote:
    Adding different size drives works fine, people just don't normally recommend it. On the nVidia array you can use their Windows tool and it lets you add drives to an active array on the fly (or remove them) so I'd look for some tool from the RAID manufacturer or for an option in the post-post controler screen.

    Now if I add a different size HD will I be able to use the entire drive or only as much as the smallest drive in the array?
  • EnverexEnverex Worcester, UK Icrontian
    edited Jun 2006
    I'm not sure, it seems to come out as a compromise when I last tried mismatched drives. I'll leave the rest to someone more versed in it than myself though.
  • Mt_GoatMt_Goat Watching the mere mortals in chaos from high atop Mt. Olympus Icrontian
    edited Jun 2006
    Bydgoszcz wrote:
    Now if I add a different size HD will I be able to use the entire drive or only as much as the smallest drive in the array?
    The smallest drive determines the size of the array.
  • edited Jun 2006
    It depends on if you're doing raid 0, raid 1 or jbod. With jbod it just adds the drives up to one big drive so their size won't matter but raid 0 or 1 you'll end up limited in size to the smallest drive in the array.
  • edited Jun 2006
    madmat wrote:
    It depends on if you're doing raid 0, raid 1 or jbod. With jbod it just adds the drives up to one big drive so their size won't matter but raid 0 or 1 you'll end up limited in size to the smallest drive in the array.

    Okay good now im making progress, so it looks like JBOD will pretty much be the only effective solution without losing hard drive space. Now for JBOD what should I use? Windows? Linux? etc... and if possible point me in the direction of a how to. ( I think with Linux I could easily use LVM of grouping or something right?)

    Also what about the backup side of things? I was hoping for something automatic that would take parity information and if a HD crashes I could rebuild it.

    One last question does JBOD stripe or just allocates files to where they will fit?


    Sorry for all the questions but this forum has so far been the biggest help, and well I have 900gb sitting on the side screaming to be filled.


    *** One thing I just ran into is MAID technology (Massive Arrays of Idle Disks) This seems to do exactly what I want check it out here Maybe somone knows how to do this?
  • edited Jun 2006
    nVidia's drivers do JBOD in Windows and in bios (I believe) as to Linux, I have no earthly idea.

    JBOD writes sequentially to each drive until it's full then to the next drive in the chain until it's full and so on. There is no redundency and if one drive fails whatever was on it is lost but you should be able to pull the data off the other drives by hooking them to another PC equipped with data recovery software.
  • EnverexEnverex Worcester, UK Icrontian
    edited Jun 2006
    JBOD just sticks files where they will go. No redundency, no speed improvement. Just like one giant drive.

    I'm sure I tried RAID0ing 2 drives once, a 10 and a 30GB drive which gave me 23GB...
  • MissilemanMissileman Orlando, Florida Icrontian
    edited Jun 2006
    Enverex wrote:
    JBOD just sticks files where they will go. No redundency, no speed improvement. Just like one giant drive.

    I'm sure I tried RAID0ing 2 drives once, a 10 and a 30GB drive which gave me 23GB...

    In RAID the size is always based off of the smallest disk - no exceptions.

    So a raid-5 of a 10, 50, 100. Comes out to 20GB. A RAID-0 comes out to 30. So on and so forth.

    JBOD (Just Bunch Of Disks) is just disk spanning so it ties all drives together into a virtualized large drive.

    You can add disks to many RAID'S now a days, but a an add in drive must be larger than the smallest drive in the array and a larger drive will be cropped down to the size of the smallest drive.

    This means you should start the array off with the largest size set of drives you can get.

    Also note that adding drives is not a casual thing. The build process has been known to quite often blow the whole array should something happen before integration is complete. The integration is generally VERY slow sometimes taking weeks to complete and gets slower the more drives are involved.

    Just FYI.
  • edited Jul 2006
    Hey there,

    just been reading this post and bit worried / confused. does this apply to raid 5 as well.. ie i have a raid 5 array of 4 9.1gig scsi's. i want to add 3 36gig scsi's. will i get to use the full space of these new drives? is there a way around this? or do i have to really buy all 9.1 gig drives or replace all of them?

    thx for your help

    Twiggy
  • edited Jul 2006
    twiggy wrote:
    Hey there,

    just been reading this post and bit worried / confused. does this apply to raid 5 as well.. ie i have a raid 5 array of 4 9.1gig scsi's. i want to add 3 36gig scsi's. will i get to use the full space of these new drives? is there a way around this? or do i have to really buy all 9.1 gig drives or replace all of them?

    thx for your help

    Twiggy


    From the conclusion I came to the array is determined by the smallest drive multiplied by the number of drives you have. ( Subtract one drive for parity information) so unless you replace all 9.1gig drives your array will only be 6 x 9.1gig
  • MissilemanMissileman Orlando, Florida Icrontian
    edited Jul 2006
    No exceptions. Always based off size of smallest disk. Best bet would be to create a separate RAID out of the new disks or you will lose a LOT of space.
  • edited Jul 2006
    ok so i have a an old compaq proliant 5500 server i got off ebay a while ago to learn about server stuff and linux. so are you saying my raid controller (in theory at least) could deal with creating 2 raid arrays so it shows up as 2 drives on the server?

    i am completely new to this line of thought, (if u couldnt tell :P). going down that line of thinking can it do multiple raids say for example i set up 3 seperate raids? i have 10 hotswap bays in total. 6 empty at the moment. eventually i will get rid of the 9.1gig drives but just finished uni so money is thin on the ground.

    thx

    Twiggy
  • MissilemanMissileman Orlando, Florida Icrontian
    edited Jul 2006
    Should be able to do it just fine.

    You'll be able to add it to the OS just like any blank new unformatted hard drive.

    I have 4 RAID's of various types and sizes on 2 controllers in my machine right now.

    Servers been doing that for years
  • edited Jul 2006
    wicked.. thx.. had me worried for a bit there.. but there is light at the end of the tunnel.

    cheers guys :)
  • edited Jul 2006
    :thumbsup: Hey all...noobie here.

    How about this; I built my own pc with a RAID array (mirror) using a 160GB hard drive and a 250GB hard drive (both Hitachi). I know that I only am using 157GB across both drives. What if I want to swap out the 160GB and add that second 250 (the one that wasn't on sale when I began this project)?
    Will I be stuck with the smaller format?

    Epox 9NPA+Ultra mobo
    AMD64 X2 4200 cpu
    Corsair XMS DDR dual channel ram, 1GB total
    PNY 6600GT 128mb video card
    Creative X-Fi Sound Blaster
    WinXP Pro
  • MissilemanMissileman Orlando, Florida Icrontian
    edited Jul 2006
    Not really. Just delete the array. Remove the 160, add the 250. Recreate the array copying from the original 250 to the new one. Run Partition Magic or some such and enlarge your partition to the new size.
  • edited Jul 2006
    ;) Thanks Missileman...

    ...first, how do you "delete the array"?

    ...second, is there any file loss when you repartition?
  • MissilemanMissileman Orlando, Florida Icrontian
    edited Jul 2006
    Well you'll have to find the info on your controller. It'll usually post a setup key combo during bios post (Nvidia is F10). You can delete the array from that menu. Just remember to stay away from anything that says clear data during the removal and creation of the new array.

    If you use partition magic it doesn't actually do anything to the data. Just moves the volume endpoint of the partition so data stays intact.

    These are really very safe procedures if you know what you are doing. The risk goes up dramatically if you don't. It can be easily done though. Just take your time and be very careful. Make sure you have a drive image (backup) before you start. I use Acronis True Image 9 and make an image to a network backup drive I have on my network. Then I can put the image back on the drive if anything goes wrong. Actually I do it all the time since i play with my RAID configurations weekly.

    If you have an image you are pretty much bulletproof on your data.

    I can restore my whole system in about 15 minutes using TI9.

    Just be careful and make double sure you have all your data backed up in a couple of places and then take your time and pick your way through it. You can explore inside these menus and such without actually making changes so you can see what you are getting in too.
  • edited Jul 2006
    Missileman wrote:
    In RAID the size is always based off of the smallest disk - no exceptions.

    So a raid-5 of a 10, 50, 100. Comes out to 20GB. A RAID-0 comes out to 30. So on and so forth.

    JBOD (Just Bunch Of Disks) is just disk spanning so it ties all drives together into a virtualized large drive.

    You can add disks to many RAID'S now a days, but a an add in drive must be larger than the smallest drive in the array and a larger drive will be cropped down to the size of the smallest drive.

    This means you should start the array off with the largest size set of drives you can get.

    Also note that adding drives is not a casual thing. The build process has been known to quite often blow the whole array should something happen before integration is complete. The integration is generally VERY slow sometimes taking weeks to complete and gets slower the more drives are involved.

    Just FYI.

    =============
    Could I partition a second larger drive with one partition the same size as the first smaller drive and a second partion with whatever space is left, and then RAID 0 the first drive and the matching partition of the second drive. Then, could I have a left over partition as an extra storage volume?

    I'm working with Mac OS X.
  • MissilemanMissileman Orlando, Florida Icrontian
    edited Jul 2006
    Super88 wrote:
    =============
    Could I partition a second larger drive with one partition the same size as the first smaller drive and a second partion with whatever space is left, and then RAID 0 the first drive and the matching partition of the second drive. Then, could I have a left over partition as an extra storage volume?

    I'm working with Mac OS X.

    No you couldn't. When a RAID controller downsizes a drive all remaining space is gone and not accessable as long as the drive is part of an array. It does this because the drives are not spanned as everyone thinks. They are striped together. In otherwords woven together. If you write a 32Kb file to a 2 drive RAID-0 with an 8K stripe it writes 8K to drive 1, 8K to drive 2, 8K to drive 1, and 8K to drive 2. So 32K is written in 4 alternating chunks to 2 drives. Therfore both drives must exactly match on space.
  • perryjonesperryjones Iowa
    edited Aug 2006
    One thing the replacement drive has to be of the same size if you use an image other wise you wind up reinstalling windows.
  • edited Mar 2009
    twiggy wrote:
    Hey there,

    just been reading this post and bit worried / confused. does this apply to raid 5 as well.. ie i have a raid 5 array of 4 9.1gig scsi's. i want to add 3 36gig scsi's. will i get to use the full space of these new drives? is there a way around this? or do i have to really buy all 9.1 gig drives or replace all of them?

    thx for your help

    Twiggy

    Twiggy,

    What people have been saying doesn't seem entirely true.

    Keep in mind that you can make an array of arrays (at least in Linux). So, in your situation, I would create a raid5 array of your four 9.1gig disks, and then another raid5 array of your three 36gig disks. Then I would go ahead and create ANOTHER raid0 array to combine those.

    Hope this helps.
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