On 14/02/17 07:58 PM, John R Pierce wrote:> On 2/14/2017 4:48 PM, tdukes at palmettoshopper.com wrote: >> 1- Better to go with a hardware RAID (mainboardsupported) or software? > > I would only use hardware raid if its a card with battery (or > supercap+flash) backed writeback cache, such as a megaraid, areca, etc. > otherwise I would use mdraid mirroring. > > >> 2 - Can an existing drive with data on it be used as aRAID drive without >> losing current data? > > software mdraid will let you add a mirror to an existing disk. or if > its using LVM, you can mirror in LVM now.Note; If you're mirroring /boot, you may need to run grub install on both disks to ensure they're both actually bootable (or else you might find yourself doing an emergency boot off the CentOS ISO and installing grub later).>> 3 - Can additional drive(s) be added later with a changein RAID level >> without current data loss? > > Only some systems support that sort of restriping, and its a dangerous > activity (if the power fails or system crashes midway through the > restriping operation, its probably not restartable, you quite likely > will lose the whole volume)... with LVM mirroring, you can add more > pairs of drives as additional mirrors to the volume group. > >-- Digimer Papers and Projects: https://alteeve.com/w/ "I am, somehow, less interested in the weight and convolutions of Einstein?s brain than in the near certainty that people of equal talent have lived and died in cotton fields and sweatshops." - Stephen Jay Gould
On 2/14/2017 5:08 PM, Digimer wrote:> Note; If you're mirroring /boot, you may need to run grub install on > both disks to ensure they're both actually bootable (or else you might > find yourself doing an emergency boot off the CentOS ISO and installing > grub later).I left that out because the OP was talking about booting from a seperate SSD, and only mirroring his data drive. -- john r pierce, recycling bits in santa cruz
On 14/02/17 08:12 PM, John R Pierce wrote:> On 2/14/2017 5:08 PM, Digimer wrote: >> Note; If you're mirroring /boot, you may need to run grub install on >> both disks to ensure they're both actually bootable (or else you might >> find yourself doing an emergency boot off the CentOS ISO and installing >> grub later). > > I left that out because the OP was talking about booting from a seperate > SSD, and only mirroring his data drive.Ah, ok, that makes sense. -- Digimer Papers and Projects: https://alteeve.com/w/ "I am, somehow, less interested in the weight and convolutions of Einstein?s brain than in the near certainty that people of equal talent have lived and died in cotton fields and sweatshops." - Stephen Jay Gould
> -----Original Message----- > From: CentOS [mailto:centos-bounces at centos.org] On Behalf Of John R > Pierce > Sent: Tuesday, February 14, 2017 8:13 PM > To: centos at centos.org > Subject: Re: [CentOS] RAID questions > > On 2/14/2017 5:08 PM, Digimer wrote: > > Note; If you're mirroring /boot, you may need to run grub install on > > both disks to ensure they're both actually bootable (or else you might > > find yourself doing an emergency boot off the CentOS ISO and > > installing grub later). > > I left that out because the OP was talking about booting from a seperateSSD,> and only mirroring his data drive. >Thanks!! I'm only considering a SSD drive due to the lack of 3.5 drive space. I have unused 5.25 bays but I'd have to get an adapter. I probably don't need to go the RAID 10 route. I just need/would like some kind of redundancy for backups. This is a home system but over the years due to HD, mainboard, power supply failures, I have lost photos, etc, that can never be replaced. Backing up gigabytes/terabytes of data to cloud storage would be impractical due to bandwidth limitations. Just looking for a solution better than what I have. A simple mirror is more than I have now. I'd like to add another drive for redundancy and go from there. What should I do? TIA