On Tue, Jan 5, 2021 at 12:31 PM Chris Murphy <li...@colorremedies.com> wrote:
> On Tue, Jan 5, 2021 at 6:24 AM Richard Shaw <hobbes1...@gmail.com> wrote: > > Ok, so not so bad. The main reason I'm considering raid5 is that I have > one 4TB drive right now, if I add 2 more with raid one, I'm only going to > get 2TB. I know it's kind of a duh, you're mirroring and right now I have > no redundancy, but this is for home use and $$$/TB is important and I can't > fit any more drives in this case :) > > Adding 2 drives at a time to Btrfs raid1 is trivial, you just add each: > btrfs dev add /dev/3 /mnt > btrfs dev add /dev/4 /mnt > > Implies both mkfs and resize. You don't need to balance it. > Ok, but my current drive is ext4 formatted. I could convert it in place but I just did that with my home drive on my desktop and it does take a while to create and remove the ext2_saved image. Wouldn't it be better to create a 2 drive raid1 array, copy the files over, update fstab, and then add the original drive to the raid1 array? As far as balancing, I wasn't sure it was helpful but was thinking of just spreading the data around :) > For btrfs raid5 that is also true, it'll just make new block groups > that have more stripes. But depending on the sizes of all the drives > it'll probably be more efficient utilization of space to rebalance. > Note if you add two drives that are bigger than the others, once the > others fill up, you'll get block groups made of two chunks on the two > drives with remaining space and that's effectively raid1 utilization, > because it's 1 data strip and 1 parity strip to do raid5 on two > devices. > In my case I'm going to use identical drives. Unique to Btrfs, you can start raid1 today, add drives, and move to > raid5 later. It's just a balance with a conversion filter. > That's pretty cool. 2TB of additional space will be plenty for now. > > Obviously if I go raid5 I won't have this option unless I can > temporarily house my data on a separate drive. > > > > Looking at the link it looks like I'm OK? > > > > # smartctl -l scterc /dev/sda1 > > smartctl 7.1 2019-12-30 r5022 [x86_64-linux-5.9.16-200.fc33.x86_64] > (local build) > > Copyright (C) 2002-19, Bruce Allen, Christian Franke, > www.smartmontools.org > > > > SCT Error Recovery Control: > > Read: 100 (10.0 seconds) > > Write: 100 (10.0 seconds) > > yeah if that's the default it's fine. The kernel's command timer is > 30s, so the drive will give up on a read/write error before the kernel > will think it's MIA. > Good deal, so raid1 for now, hopefully raid5/6 support will be better if I need to convert later. Thanks, Richard
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