November 9, 200916 yr What is the difference between Online Capacity Expansion found in many RAID controller cards compared to the software-based expansion options in unRAID in regards to expanding a RAID? I would like to have 3x 1TB drives in a RAID5, with the ability to expand the RAID with additional 1TB drives without the need for reformatting the entire RAID. Is that typically doable with a RAID card that supports OCE? Is that possible with unRAID? Whats the best route? I'm very computer literate in terms of hardware and software, but this is the first time I've ever tackled a RAID setup. I've been tearing through hard drive space now that I'm storing Blu-Ray movies, and in addition to building a new HTPC, I'm looking into the smartest long-term storage solution for my media.
November 9, 200916 yr OCE is essentially expanding a partition. Its slow and IMHO very very risky (i have seen 3 RAID 5 arrays completely break during expansion). unRAID works completely different tot that and doesnt bugger about with existing data to expand. Its worth spnding 30 mins reading our wiki it will explain alot and allow you to see yourself what uNRAID is better in many ways.
November 9, 200916 yr What is the difference between Online Capacity Expansion found in many RAID controller cards compared to the software-based expansion options in unRAID in regards to expanding a RAID? Traditional raid solutions stripe data and the parity across all drives in the raid set. Thus when you add a new drive the data and parity needs to be redistributed across the entire array including the new drive. Unraid does not stripe the parity data at all and has no real concept of a 'raid set'. You simply have independant drive volumes formatted with a standard reiserfs filesystem and then a seperate (hidden) parity disk which holds all your non striped parity data. So when you insert a new disk there is no need for any OCE as there are no data or parity stripes. There are community tools (preclear.sh) which can test and configure your drive for unraid before it is added to the array. This means that then adding it to the array literally takes a couple of minutes and involves stopping and starting the array only once. I would like to have 3x 1TB drives in a RAID5, with the ability to expand the RAID with additional 1TB drives without the need for reformatting the entire RAID. Is that typically doable with a RAID card that supports OCE? Is that possible with unRAID? Whats the best route? Yes this would be do-able with a RAID card that supports OCE. It is also possible with unraid but again, unraid is a very different concept from any sort of standard RAID configuration. Were you to do this with unraid you would end up with two independent reiserfs volumes and one parity disk. You can then add 1TB drives up to the limit unraid supports (currently 20? someone please correct me if that's wrong!) without reformatting anything and all, except for a couple of minutes window whilst the array restarts and the actual power off to fit the disk, without any array downtime. The best route is largely up to yourself. The question of RAID versus unraid is really the single biggest question you can ask. Breifly as unraid does not stripe data or parity your data (in my opinion) is very safe. All the data disks are standard volumes and so in case of emergency can be attached to any other system and just read and interacted with as a standard reiserfs volume. What this means is that if, in the worst case scenario, two of your disks were to fail at the same time (thus losing your parity protection) the data on the remaining disks would be left entirely intact. You would have data loss but only partially. If the same were to happen on a raid volume (excluding raid6 of course which would allow for two drive failures, so in that case assume three failures!) then you would lose the entire volume and all your data. Other advantages are per drive spin down for power and (hypothetical) hardware savings and 'mix and match' expandability (don't have to worry about all the drives being the same size - so long as the parity disk is as large or larger than any other disk in the array). The main drawback of unraid as opposed to RAID is the write speed. This is continually being addressed (latest beta improves it by almost 100%). The second drawback is that it's distribution based and not open source which in terms of long term support and durability means you're at the behest of limetech updates. A software RAID stack (and to an extent a hardware raid stack) is much more independent. As NAS suggested spend some time looking round the forums and the wiki as there is alot of info to help you make your choice. Feel free to ask questions if you need things clearing up or explained in more detail. I'm very computer literate in terms of hardware and software, but this is the first time I've ever tackled a RAID setup. I've been tearing through hard drive space now that I'm storing Blu-Ray movies, and in addition to building a new HTPC, I'm looking into the smartest long-term storage solution for my media. I'm of the opinion that any solution that is 'best fit' right now, will not necessarily be best fit in 2-3 years time due to hardware and software advances. However you can certainly look to maximise your storage opportunities in that time frame!
November 9, 200916 yr I appreciate the quick feedback and the relatively unbiased answers, considering the forum. I've dug through the Wiki (granted, at 3am) and one of the things I hadn't stumbled across yet was any way to have the entire volume share show up as one drive letter, this way discs are backed up to one drive letter only, and played back from the same. While it's not a challenge for me to pick where the rip goes to, it needs to be user-friendly enough for the wifey to just pick "copy disc" and be done. I've finally gotten all of my software solutions in place for backup, management and playback to a point where the system needs zero instruction to use. Now just a matter of finding a good way to store all the data, and this project can finally come to an end. For now.
November 9, 200916 yr I appreciate the quick feedback and the relatively unbiased answers, considering the forum. I've dug through the Wiki (granted, at 3am) and one of the things I hadn't stumbled across yet was any way to have the entire volume share show up as one drive letter, this way discs are backed up to one drive letter only, and played back from the same. While it's not a challenge for me to pick where the rip goes to, it needs to be user-friendly enough for the wifey to just pick "copy disc" and be done. I've finally gotten all of my software solutions in place for backup, management and playback to a point where the system needs zero instruction to use. Now just a matter of finding a good way to store all the data, and this project can finally come to an end. For now. unraid calls this feature 'user shares' and basically conglomerates all your individual drives into one big 'virtual' drive. Writes are then assigned to the correct individual drive based on an algorithm you set via the web interface. In my case I use 'most free' which copies the data onto the disk with the most free space. It is slightly more complicated than that as unraid has a concept of 'split levels'. The wiki and other forum posts will be able to give you a much better description of that than I can manage though! So yes, you can do what you want. Here is a quick snippet of my disk output from the unraid server : root@192:~# df -h Filesystem Size Used Avail Use% Mounted on /dev/sdf1 3.8G 441M 3.4G 12% /boot /dev/md4 932G 738G 194G 80% /mnt/disk4 /dev/md2 1.4T 1.2T 195G 87% /mnt/disk2 /dev/md1 1.4T 1.2T 169G 88% /mnt/disk1 /dev/md3 1.4T 1.2T 183G 87% /mnt/disk3 shfs 5.1T 4.3T 740G 86% /mnt/user root@192:~# /mnt/user is the virtual drive. You can then share this to your windows PC's and map it as a network drive as you see fit. There is a slight performance penalty for using this feature but not enough to be a concern.
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