On Sunday 28 February 2010, Dustin J. Mitchell wrote:
>I'm glad my tarball worked for you. I'll find out from Jean-Louis how
>to generate snapshots with the datestamp, in case I need to do so in
>the future.
>
>But you've brought up a new topic, so I've changed the subject line:
>
>On Sun, Feb 28, 2010 at 8:40 AM, Gene Heskett <[email protected]>
wrote:
>> WARNING: shop /home: fallback_splitsize of 10240k < 0.1% of tape size and
>> may be used for PORT_DUMP; check your configuration
>>
>> A line for every dle. Is this something I need to address before
>> tonights real run?
>
>Yes, I just added this warning. Some refinement may be in order, so
>let me know what you think.
>
>The problem is that Amanda's fallback_splitsize defaults to 10M, and
>I've seen a number of users recently who are using this splitsize for
>multi-terabyte dumps, without knowing it. This generates *terrible*
>performance on backup, since the tape drive has to write tens or
>hundreds of thousands of filemarks, and also on recovery, since the
>recovery app must seek to and read from each of those many thousands
>of files.
OhmyGawd. Plumb deadly for tape users.
>This is usually due not to a "fallback" in an error condition, but to
>misconfiguration. The splitsize parameters are *very* confusing!
I almost understood them, so it can't be too bad, but then it doesn't seem to
be a consideration here. ;-)
>So the new warning is intended to alert folks such as yourself to the
>potential misconfiguration. It's just a warning, so Amanda will
>continue to run as before, but you really should fix it. To fix it,
>do one of:
>* set split_diskbuffer properly
>* raise your fallback_splitsize to something larger than 0.001 *
> tape-length * set fallback_splitsize to 0
>
>> Also, where do I find the definition of a PORT_DUMP? That is a new one
>> to me.
>
>Oops, that should say PORT-WRITE. PORT-WRITE is a dump straight to
>the device, without going to holding first. Amanda does PORT-WRITE
>when the DLE is larger than the holding disk, or when no holding disk
>is configured. It is the opposite of FILE-WRITE, which is a write
>from holding disk to the tape device.
Ahh, clarified, for me at least. As I have holding disk out the yang, and am
using v-tapes anyway, it hadn't stuck up its hand and waved at me before.
Would this not also result in individual split sized files I could see in my
/amanatapes/Dailys partition? In which case it has only happened once that
I'm aware of.
>Amanda always uses the tape_splitsize for FILE-WRITE dumps. It does
>the same for PORT-WRITE, but if split_diskbuffer is not set, which is
>the case on your system, then it uses fallback_splitsize instead (with
>its default of 10M), with no notice of the "fallback".
>
>So what if I changed the warning to read
>
>WARNING: shop /home: fallback_splitsize of 10240k < 0.1% of tape
>length and may create >1000 parts; set split_diskbuffer or increase
>fallback_splitsize
I'd make a note in the example/amanda.conf that this is related to the memory
the machine has, and while it can use swap, this shouldn't normally be more
than say 50% of the memory in the machine. I have 4GB of ram, and 4 to 8 GB
of swap but I don't let it get too far into swap without doing a swapoff -a,
swapon -a to clean up the mess.
This wording makes it more verbose, but certainly worth it for the clarity,
I'd go for it. However, on consideration it may be worthwhile to issue the
warning only when a "df /dump's" free space is less than say 2x the tapesize.
/dumps here is on /, which is a 1TB drive here. Here is mine:
[r...@coyote dumps]# df /dumps
Filesystem 1K-blocks Used Available Use% Mounted on
/dev/sda3 100790036 9563148 86106976 10% /
Not a lot of use bothering the folks if the warning is just another cry of
'wolf'. There really _should_ be a wolf at the door... ;)
>I'll also add a wiki page to help explain the background for the error.
Good idea, and I can find the link.
>Let me know what you think.
See above.
Thanks, Dustin
>P.S. There are plans afoot to change these configuration parameters to
>something less confusing, but not in the upcoming release.
>
I suppose they will bite me when that occurs. ;) NBD, I've been forewarned.
--
Cheers, Gene
"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Duty, n:
What one expects from others.
-- Oscar Wilde
