FAQ
There is an option on some hard drives that is off by default (under
windows) called lazy writing.

You would need to go into the driver and turn this on.

Only very specialized systems would ever do this.

On Nov 19, 2008, at 11:13 AM, Mark Miller wrote:

Okay, I'll admit I am trusting some else testing this. One of the
java database implementations (hsql or something?) talks about it
and tests it it to be the case also with derby and other
transaction systems. Corruption didn't appear that hard for him to
lure out at all. Also, if you google slashdot your harddrive lies
to you, there is more testing of it. I have also seen bits or
pieces about it elsewhere.

I choose to believe myself, but I will admit I was 100% wrong about
santa clause, so take it for what its worth. I havn't tested it at
all.

robert engels wrote:
I would really like to see some PROOF of these drives "lying".

If that were the case, no database system would ever be reliable
on these drives ! And data corruption would be happening all over
the place !
On Nov 19, 2008, at 10:56 AM, Mark Miller wrote:

Michael McCandless wrote:
Mark Miller wrote:
It is dangerous, but probably not any more dangerous than using
a consumer hard drive that lies to sync (don't know the
numbers, but I have to assume some/many are doing this with
Lucene - in which case you pay perf for a false sense of
security<g>).
Well, if the consumer drive is in fact lying, then sync should
be wicked fast ;) So you get a false sense of security without
paying anything!
That occurred to me as well, but they must do some work :) , or
the lie would be to just return...maybe it is. I mean if it
doesn't guarantee, whats the point...oh yeah, to fool benchmarks.
Still boggles my mind.

I wasn't being very serious though. Like I said, I'm not
suggesting we allow it to be turned off, I was just looking for
it because I wanted to debug...your option was just as good for
my case.
Not a real suggestion at this point though. Just thinking about
some of the reports I have seen of much slower indexing with
2.4 (the latest being to the solr list today). Can't imagine
why someone would see such a drastic change (I imagine you
could imagine a lot better), other than maybe the sync is
hobbling their specific situation (in which case i'd guess its
not lying if it where going to be so slow though <g> Or its AIX
or something <g>). Would be cool to be able to flip it off and
test. Sounds like thats simple enough already though. I could
whip up an off for solr testing easy enough.
Yeah let's dig down and get to the root cause here -- if turning
off sync in fact fixes the slowdown we should understand why
sync is being called so often.
Yeah, the root cause is likely elsewhere I'm sure...it would have
to be a pretty broken sync to add so much time (im fairly sure
hes using defaults so he not going to have a billion index files
to sync or something). Just captured my attention as a
possibility and I wanted to be able to test without. Most 2.3 -
2.4 changes don't seem like they would slow things down. Could be
a problem with Solr as well in this particular case though.
Mike

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postedNov 19, '08 at 2:33p
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