setting up a RAID-1 array with a non-empty hdd?
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From: Arno on 10 Mar 2010 12:48 yawnmoth <terra1024(a)yahoo.com> wrote: > On Mar 10, 7:04?am, Arno <m...(a)privacy.net> wrote: >> yawnmoth <terra1...(a)yahoo.com> wrote: >> > On Mar 9, 11:44?am, Arno <m...(a)privacy.net> wrote: >> >> yawnmoth <terra1...(a)yahoo.com> wrote: >> >> > I have a hard drive whose contents I'd like to back up. ?I was >> >> > thinking about using RAID-1 mirroring to do this. ?The thing I'm >> >> > considered about is... ?will my drive be wiped? ? >> >> >> Yes. >> >> >> > My second drive I >> >> > don't really care about - that drives purpose is to just serve as a >> >> > backup. ?But my main drive... ?I do care about that and reformating >> >> > would rather defeat the point. >> >> >> The way to do this with a decent RAID conttroller or software >> >> RAID is as follows: Set up a degraded RAID1 with the second >> >> driv. Partition it and create the filesystem. Then copy everything >> >> over from the first fdirve. And then add the frist drive to >> >> the degraded RAID1 array to get redundancy. >> > Any idea as to what RAID controllers might provide that >> > functionality? ? >> >> I don't know. Linux Software RAID does it and any good controller >> should do it, but then the question is what constitutes a good >> controller. >> >> > <http://www.rosewill.com/products/942/ >> > productDetail.htm> looked like a good RAID controller >> >> That is Fake Raid, i.e. not a RAID controller at all. I have >> one with the same chip, this is a plain 2 port SATA controller. >> What happens here is that this thing has software RAID in the >> BIOS, which turns out to be the wortst possible way to do RAID. >> >> Example of a real hardware controller:http://www.3ware.com/products/serial_ata2-9650.asp >> A bit more expensive though. > Also, is there a way to easily tell if an arbitrary card uses BIOS > software RAID or has "real" RAID controllers? And what advantage does > real RAID have over software RAID, be it Linux or BIOS? I assume less > CPU usage overhead? It used to be a speed question. It is not anymore. Basically, hardware RAID has the following advantages: - automated hotplug and rebuild, enclosure support - low/no OS dependency for Linux Software RAID you get - can work on partitions - very easy to monitor and administrate Speed-wise they are pretty much the same if the software RAID goes over a PCI-E attached controller. As to recognition, if it is > 300EUR/USD, it is hardware RAID ;-) Arno -- Arno Wagner, Dr. sc. techn., Dipl. Inform., CISSP -- Email: arno(a)wagner.name GnuPG: ID: 1E25338F FP: 0C30 5782 9D93 F785 E79C 0296 797F 6B50 1E25 338F ---- Cuddly UI's are the manifestation of wishful thinking. -- Dylan Evans |