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Date:      Fri, 14 Apr 2017 13:33:36 -0700
From:      "Ngie Cooper (yaneurabeya)" <yaneurabeya@gmail.com>
To:        Larry Rosenman <ler@lerctr.org>
Cc:        Slawa Olhovchenkov <slw@zxy.spb.ru>, "svn-src-head@freebsd.org" <svn-src-head@freebsd.org>, "svn-src-all@freebsd.org" <svn-src-all@freebsd.org>, "src-committers@freebsd.org" <src-committers@freebsd.org>, Ngie Cooper <ngie@freebsd.org>, Alan Somers <asomers@freebsd.org>
Subject:   Re: svn commit: r316938 - head/sbin/savecore
Message-ID:  <EC89EB67-7854-4DE6-BD40-2626FF993181@gmail.com>
In-Reply-To: <0CAE4B1C-228B-4C71-86E9-4337753DFF74@lerctr.org>
References:  <201704141941.v3EJfmCW003347@repo.freebsd.org> <CAOtMX2gPHWRGiE9UA5AevZz=cTv_qksAWX0H-xRjDEHp0huCVg@mail.gmail.com> <20170414201431.GF20974@zxy.spb.ru> <CEC6CDCF-2EF2-4CEF-BF54-91F3021EF262@gmail.com> <0CAE4B1C-228B-4C71-86E9-4337753DFF74@lerctr.org>

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> On Apr 14, 2017, at 13:26, Larry Rosenman <ler@lerctr.org> wrote:
>=20
> On 4/14/17, 3:19 PM, "Ngie Cooper (yaneurabeya)" =
<owner-svn-src-all@freebsd.org on behalf of yaneurabeya@gmail.com> =
wrote:
>=20
>> On Apr 14, 2017, at 13:14, Slawa Olhovchenkov <slw@zxy.spb.ru> wrote:
>>=20
>> On Fri, Apr 14, 2017 at 01:49:51PM -0600, Alan Somers wrote:
>>=20
>>> On Fri, Apr 14, 2017 at 1:41 PM, Ngie Cooper <ngie@freebsd.org> =
wrote:
>>>> Author: ngie
>>>> Date: Fri Apr 14 19:41:48 2017
>>>> New Revision: 316938
>>>> URL: https://svnweb.freebsd.org/changeset/base/316938
>>>>=20
>>>> Log:
>>>> savecore: fix space calculation with respect to `minfree` in =
check_space(..)
>>>>=20
>>>> - Use strtoll(3) instead of atoi(3), because atoi(3) limits the
>>>>   representable data to INT_MAX. Check the values received from
>>>>   strtoll(3), trimming trailing whitespace off the end to maintain
>>>>   POLA.
>>>> - Use `KiB` instead of `kB` when describing free space, total =
space,
>>>>   etc. I am now fully aware of `KiB` being the IEC standard for =
1024
>>>>   bytes and `kB` being the IEC standard for 1000 bytes.
>>>> - Store available number of KiB in `available` so it can be more
>>>>   easily queried and compared to ensure that there are enough KiB =
to
>>>>   store the dump image on disk.
>>>> - Print out the reserved space on disk, per `minfree`, so end-users
>>>>   can troubleshoot why check_space(..) is reporting that there =
isn't
>>>>   enough free space.
>>>>=20
>>>> MFC after:    7 weeks
>>>> Reviewed by:  Anton Rang <rang@acm.com> (earlier diff), cem =
(earlier diff)
>>>> Tested with:  positive/negative cases (see review); make tinderbox
>>>> Sponsored by: Dell EMC Isilon
>>>> Differential Revision:        D10379
>>>=20
>>> The free space calculation is still uselessly conservative, because =
it
>>> doesn't account for the fact that core dumps will always be either
>>> spare or compressed.  The result is that savecore will frequently
>>> refuse to save corefiles even when there's plenty of space.  I
>>> proposed removing the space check altogether in
>>> https://reviews.freebsd.org/D2587.  However, I agreed to wait until
>>> after the compressed core dump feature was merged, because then =
mostly
>>> accurate space checks will be possible.  AFAIK the compressed core
>>> dump feature still hasn't been finished.
>>=20
>> Is posible (in the future) to use multiple swaps (on multiple disks)
>> for save core dumps?
>=20
>    Multiple swap devices is already handled by savecore(8), if one =
uses fstab(5) or dumpon(8). Otherwise, you must invoke savecore(8) on =
individual devices.
>=20
>    As far as saving to multiple disks is concerned, I would hope that =
one is using a redundancy capable filesystem (zfs) or RAID-like =
technology (gmirror, graid, LSI Fusion=E2=80=99s RAID product line) to =
stripe and/or mirror the data across multiple disks.

=E2=80=A6

> How do I use multiple devices to have the system dump on all of my =
swap?  I got a message about not enough space, but there (I think) was =
enough between multiple drives=E2=80=A6.

Something like:

- Create a zpool
- Mount zpool to /crashdumps
- Change dumpdir in /etc/rc.conf to be /crashdumps, e.g., echo =
=E2=80=98dumpdir=3D/crashdumps=E2=80=99

?
HTH,
-Ngie

PS The issue with lack of space might be the issue that Alan brought up =
earlier with compressed dumps and overly conservative free space checks, =
or it might be the fact that dumpdir (default: /var/crash) is full.

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