question about software raid5 (windows server 2003)

dualblade

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i have a 2003 server system that i'd like to make into a network file server. i'm looking at picking up 4 or 5 300gb drives to use in a raid5 array. i was going to do it by having server2003 convert all the disks into dynamic disks and then use the built in raid 5 function. i realize that this will eat up cpu calculating parity but the server has no other cpu intensive tasks and, although production, is only running my home network (so far from mission critical).

my question is, if the os drive or the os itself manages to bite the dust and i have to reinstall the os, what happens to my array? is it recoverable? i know this data is usually stored on controller cards, but i'm trying to do this project as inexpensively as possible so i'm just using an ata133 card to connect multiple drives (so no controller card). that said, if my array is gone in the event of software or hardware failure, i'm going to have to rethink my situation. if anyone knows the details of windows volume raid, please give me some advice.
 

Lazn_Work

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If your OS bites the dust with any dynamic disk (RAID 5 or not, even just a single drive) it is a big PITA to get any data back off that dynamic disk. And if it is a windows software RAID 5 array, I am not even sure it is possible to recover it.

Remember though, any RAID is not a backup, they are not the same thing. RAID is to deal with a single drive failure, Backup is to deal with a server rebuild. RAID will not save you from the most common causes of data loss, only from hd failure.

==>Lazn
 

defakto

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As long as you don't put the system drive on the software raid 5 drives, If i remember, it's possible to import the dynamic disc config into windows again. Though, I'm not sure where to go from there for recovering the raid 5 drive.
 

dualblade

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thanks for the quick responses but i actually just found a link that says this process is really easy. according to this tom's hardware guide test, all you have to do is plug the drives into any system that supports windows raid5 and it will work fine. here's the link

http://www.tomshardware.com/storage/20041119/raid5-04.html


one more question:
is it possible to add disks to a windows raid 5 array to expand capacity? if i start with 3 drives but decide to add another 2 down the line, can the array be resized without having to backup, destroy the data, and recreate the array?

edit: answer to question could be via windows capabilities or 3rd party utility. can partitionmagic extend raid arrays?
 

dualblade

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scotty do said:
Im pretty sure this is only available with software raid5

what is, extending raid arrays? it seems that the better hardware raid5 controllers can do it but i don't have the money for a several hundred or thousand dollar controller card. according to the info i found, microsoft's software implementation of raid5 can't be extended or mirrored. does anyone have info to the contrary, or know of a 3rd party product that can handle the task? if i have to choose between extendability (standard jbod volume), or redundancy (raid5), well, it's not a happy choice. ideally i'd like both as i don't have enough money to purchase all the drives i need now. i have a drive temporarily available to move data to while i create the array, but it will be gone soon so i could really use an answer as soon as possible. thanks for the help
 

DougLite

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A) Windows will not allow the boot volume to reside on any dynamic volume that requires more than one disk to remain online. This rules out booting from striped, spanned, or RAID-5 volumes. You may boot from simple or mirrored volumes.

B) Mirrored, Striped, and RAID-5 volumes may not be extended. The only way to make one of these volumes larger is to backup the data on it, delete the volume, and create a new one of the appropriate size/number or disks.

C) A dynamic volume, presuming that enough disks are migrated to make the volume at least "at risk," or better yet "healthy" may be imported into a new system using the Disk Management MMC snap-in.

Also, writes using RAID-5 volumes are extremely system intensive as two reads and one write must be executed to complete a write operation. Any other questions?
 

defakto

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For point B youre only refereing to software raid, right? I know some hardware raid cards do support adding disks to an array.
 

DougLite

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Correct, that is a limitation of the DMIO system in Windows NT products.
 

dualblade

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the system uses a 12gb drive for the OS. the drives in question are strictly data.

if i decided to do a jbod/span/whatever windows calls it and a drive fails, is the whole span dead? if i sense that a drive is about to die, can i ask windows to replicate the contents of that drive onto a new drive to then be inserted in the span?

doug, do you know of 3rd party software that can extend raid5 volumes? do you know of a cheap pata controller card that can handle this if no 3rd party software exists?

i only have enough money to buy 3 drives at first (300 gig each) so with raid5 that would create a 600gig volume. if i was to grow the volume and had to remake the raid5 array down the line, there's realistically no place i could put 600gig worth of data. because of this, i'm not sure if i can use raid5 if there's no way to expand it.

i'm not too worried about system intensive I/O because data will only come onto those drives as it's downloaded from the net, and retrieved as the video is viewed. the server is for my archived movies/tv shows and playing them across the network is not very bandwidth intensive (and therefore not a big load on the server's I/O ability). there is basically no situation where i'll need to copy large files over to the server or retrieve entire large files at once. i'm keeping a storage drive on my pc (200gb) that holds things that i would see a slowdown if accessed across the network.
 

DougLite

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A) A spanned volume has one file system for all of the disks that are members of the volume. So yes, if a drive does out, the file system is trash and it will be inaccessible to Windows. You may be able to use low level recovery tools, assuming that none of the files you want to recover were all or in part on the dead drive.

B) It is (to my knowledge) impossible, or at best unsafe, to extend a software RAID-5 volume by adding another disk to it. It is not supported by MS, and I am not aware of any third party tools for online capacity extension of Dynamic RAID-5 volumes. Your only choice here is a hardware RAID-5 card that supports this capability natively.

C) A card that supports OCE will not come cheap. If you've never heard of 3Ware, Acrea, LSI, or Adaptec, prepare yourself for some sticker shock :(
 

Ice Czar

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DougLite said:
DMIO system

err... I have a question :p

whats DMIO?
(I knew there was a reason I nominated you for mod :p )

Dynamic Mode Input Output?
 

ohknats

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I ran a software RAID 5 under 2003 until I bought the Areca card. It worked but it is SLOW! Don't expect any over 5MB/s sustained and 7MB/s burst transfers.

If your looking to stay on the cheap IMO I would at least still pop a few bills for an LSI or broadcom card that is host based.
 
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