On Tuesday 15 June 2010 09:47:11 cool name wrote: > Mike Bird-2 wrote: > > Do you really want to use hardware RAID? Note that if your hardware RAID > > controller dies, you're going to need a compatible replacement or you'll > > lose all of your data. > > utter bullshit. Is it true that not EVERY replacement-controller will do > the job but most out there will, RAID is standardized, you know .... only > if you use proprietary RAID-version you'll be fucked up, anything else > will be most likely fine. That's simply not true. The RAID numbers are loosely defined, so one manufacturer's RAID 5 parity data may not be compatible with another manufacturer's. The mdadm software RAID tool for Linux supports at least 4 RAID 5 parity algorithms. RAID 6 is part of the "RAID standard", but few manufacturers implement it, and its second parity calculation is even more loosely defined. RAID 0 is likely fine, as long as you know the stripe size in use and your new controller supports it. RAID 1 is likely fine, but some HW controllers only support it on exactly 2 drives. RAID 2, 3, and 4 are basically never used now; good luck finding a HW RAID controller that supports one of them. Strictly layered RAID 1/0 would be fine, again as long as your stripe size is know, but rarely is RAID 1/0 done in a strictly layered fashion. Again, mdadm has 3 different algorithms for how to place the second (or third...) copies of that data, and supports RAID 1/0 on an uneven number of drives, which can't be done when things are strictly layered. Finally, there is no standard for how a RAID header / the RAID meta-data is written to the disks are read at boot time. Something has to indicate what array a drive is part of, what RAID level is in use on that array, what disk number the drive is within the array, and the RAID-level-specific options like stripe size. With HW RAID, this is always stored in a completely proprietary manner. Unless you have a very specific workload where mdadm might cause a performance slip, I recommend using mdadm for all your RAID. -- Boyd Stephen Smith Jr. ,= ,-_-. =. bss@iguanasuicide.net ((_/)o o(\_)) ICQ: 514984 YM/AIM: DaTwinkDaddy `-'(. .)`-' http://iguanasuicide.net/ \_/
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