Adding Different Size Hard Drives to RAID Arrays? Possible?
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.
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.
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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?
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?
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.
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.
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
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
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
cheers guys
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
...first, how do you "delete the array"?
...second, is there any file loss when you repartition?
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.
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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.
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.