Re: Question about continous blocks for inode due to 'no space left on device' problem

[Michel Verbraak <info1stsetup@xxxxxxxxx>]

2016-02-05 23:30 GMT+01:00 Dave Chinner <david@xxxxxxxxxxxxx>:

On Fri, Feb 05, 2016 at 02:13:00PM +0100, Michel Verbraak wrote:
> All,
>
> Recently we ran into a problem where our filesystem (300GB in size)
> reported 'no space left on device' (ENOSPC) but when we looked at disk
> space usage and inode usage it was around 52% for disk space and 11% for
.......

>
> Store 03 (root@server):~# xfs_db -c freesp /dev/sdb
>  from   to extents blocks  pct
>Â Â Â Â1Â Â Â Â1 3282633 3282633Â Â9.03
>Â Â Â Â2Â Â Â Â3 3416223 8372325Â 23.03
>Â Â Â Â4Â Â Â Â7 6175009 24700036Â 67.94

Yup, no more aligned 4 block extents in the filesystem.

Dave Thank you for your answer but are you able to explain a bit more on how you determine there are no aligned 4 block extends available?

It apparently is not the 'from 4 to 7' line telling there are at least continuous extents of 4 blocks big. Or is it because 24700036 divided by 6175009 is exactly 4 and not a bit more?

When I calculate the ratio between the individual AG freesp they were all four exactly 4.

As said we would like to detect this problem from happening again. And we would like this detection to be done by our monitoring service.

One of my colleagues mentions the following calculation to find out if there are enough aligned 4 block extents:

Starting from line "from 4 to 7" calculate: <blocks-column> - (4 * <extents-column>) > 0. When not there is not enough free space for new inodes.

On another system we have which does not see these problems yet we have:

 from to extents blocks pct
ÂÂÂÂÂ 1ÂÂÂÂÂÂ 1 3483987 3483987ÂÂ 7.83
ÂÂÂÂÂ 2ÂÂÂÂÂÂ 3 3560607 8709838Â 19.58
ÂÂÂÂÂ 4ÂÂÂÂÂÂ 7 6402893 26486634Â 59.55
ÂÂÂÂÂ 8ÂÂÂÂÂ 15Â 418450 5799206Â 13.04

26486634 / 6402893 = 4.136666 and

26486634 - (4 * 6402893) = 875062 > 0 and
5799205 - (4 * 418450) = 4125405 > 0

Â

into this condition.

Cheers,

Dave.
--
Dave Chinner
david@xxxxxxxxxxxxx

Michel.