On Sun, 06 May 2012 12:18:33 +0000, Camaleón wrote: > On Sun, 06 May 2012 11:46:21 +0000, Ramon Hofer wrote: > >> On Sat, 05 May 2012 11:15:22 +0000, Camaleón wrote: > >>>> On the other hand it isn't possible to have different disk sizes in a >>>> raid 6 neither. >>> >>> I think yes, that you can, but only the lowest of the disk capacities >>> will be used (this applies to all of the RAID levels). Software RAID >>> has not such limitaion because you can mirror partitions, instead. >> >> Ok so with sw raid I can use partitions as devices. This means I could >> divide my drives into 500 GB pieces and like this use the whole size of >> the disks? > > If your hard disk capacity is ~1.5 TiB then you can get 3 partitions > from there of ~500 GiB of size (e.g., sda1, sda2 and sda3). For a second > disk, the same (e.g., sdb1, sdb2 and sdb3) and so on... or you can make > smaller partitions. I would just care about the whole RAID volume size.
Sorry I don't get it. Let's assume I have 4x 1.5 TB and 4x 2 TB. I divide each drive into 500 GB partitions. So three per 1.5 TB and four per 2 TB disk. Then I put the 28 partitions (4x3 + 4x4) in a raid 6? >> Wouldn't it be easier to have e.g. four of each size and put them into >> raid5? > > With software raid you have more choices because you can partition as > you like: you can use the whole disk capacity or make small chunks and > use them to be part of a RAID volume. > > Again, RAID5 is not something advisable and mdadm also supports RAID 6 > :-) > >>>> So my plan seems still reasonable to me to have several 4 disks raid >>>> 5 arrays. Like that I'm flexible to add bigger disks in future as >>>> they become cheaper and still can keep my old 1.5 TB disks. And if I >>>> would go for raid 6 with the 4 disk array I would loose a third of >>>> the capacity. >>> >>> (...) >>> >>> You've been warned :-) >> >> Yes and I appreciate that! >> But I can't see any other solution without loosing 500 GB of the two TB >> disks :-? > > When using the whole hard disk capacity for the array: > > - A RAID 5 volume with x4 1.5 TiB disks will give you an available space > of 4.5 TiB (the sum of the number of the disks minus 1 drive). > > - A RAID 6 volume with x4 1.5 TiB disks will give you an available space > of 3 TiB (the sum of the number of the disks minus 2 drives). > > That's the price for the added data security. If you are constrained > about hard disk space, remember that you can add LVM and your spacing > problems are be solved >;-) My problem is that I don't have much experience with raid. Only about the two years where I only had one drive failure which was false alarm. I could put it right back in. So I think I'll have to burn my fingers myself to understand the little (or maybe even misleading in some sense) security of raid5... -- To UNSUBSCRIBE, email to [email protected] with a subject of "unsubscribe". Trouble? Contact [email protected] Archive: http://lists.debian.org/[email protected]
