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Date:      Fri, 14 Apr 2017 13:19:49 -0700
From:      "Ngie Cooper (yaneurabeya)" <yaneurabeya@gmail.com>
To:        Slawa Olhovchenkov <slw@zxy.spb.ru>
Cc:        Alan Somers <asomers@freebsd.org>, Ngie Cooper <ngie@freebsd.org>, "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>
Subject:   Re: svn commit: r316938 - head/sbin/savecore
Message-ID:  <CEC6CDCF-2EF2-4CEF-BF54-91F3021EF262@gmail.com>
In-Reply-To: <20170414201431.GF20974@zxy.spb.ru>
References:  <201704141941.v3EJfmCW003347@repo.freebsd.org> <CAOtMX2gPHWRGiE9UA5AevZz=cTv_qksAWX0H-xRjDEHp0huCVg@mail.gmail.com> <20170414201431.GF20974@zxy.spb.ru>

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> 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?

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.

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.

Thanks!
-Ngie

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