Re: Rebalancing RAID1

[Hugo Mills <hugo@carfax.org.uk>]

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On Thu, Feb 14, 2013 at 01:41:04AM -0700, Chris Murphy wrote:
> 
> On Feb 14, 2013, at 12:58 AM, Fredrik Tolf <fredrik@dolda2000.com> wrote:
> > 
> > Feb 14 08:32:30 nerv kernel: [180511.760850] lost page write due to I/O error on /dev/sdd1
> 
> Well, someone else might comment on what that is exactly, I'm not getting conclusive google hits on this. Sometimes it's fixed by going to a newer kernel. Sometimes it's bad hardware. But it's apparently not a btrfs error. But it's causing subsequent errors which are btrfs errors. So whatever it is, it seems like btrfs doesn't like it.
> 
> 
> > Feb 14 08:32:30 nerv kernel: [180511.764690] btrfs: bdev /dev/sdd1 errs: wr 288650, rd 26, flush 1, corrupt 0, gen 0
> 
> So there continue to be write errors. Unsurprising as sdd1 seems to be dropping pages.
> 
> >> 
> >> Scrubbing does not balance the volume. Based on the information you supplied I don't really see the reason for a rebalance.
> > 
> > Maybe my terminology is wrong again, then, because I do see a reason to get the data properly replicated across the drives, which it doesn't seem to be now. That's what I meant by "rebalancing".
> 
> How much data was copied to the drives? I'm continuously confused by how btrfs reports data usage. What I have is this from fi show and fi df:
> 
> Data, RAID1: total=2.66TB, used=2.66TB

   This is the amount of actual useful data (i.e. what you see with du
or ls -l). Double this (because it's RAID-1) to get the number of
bytes or raw storage used.

> Total devices 2 FS bytes used 1.64TB
> devid    1 size 2.73TB used 1.64TB path /dev/sdi1
> devid    2 size 2.73TB used 2.67TB path /dev/sde1

   This is the amount of raw disk space allocated. The total of used
here should add up to twice the "total" values above (for
Data+Metadata+System).

> So I can't tell if it's ~1.64TB copied or 2.6TB.

   Looks like /dev/sdi1 isn't actually being written to -- it should
be the same allocation as /dev/sde1.

   Hugo.

-- 
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