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Re: Very long deletion time on a 200 GB database



On 02/27/2012 07:14 AM, Shaun Thomas wrote:
On 02/27/2012 08:59 AM, Reuven M. Lerner wrote:

From what I understand, the issue isn't one of current disk space,
but rather of how quickly the disk space is being used up.

Noted. Just keep in mind that dead rows are not free. In the case of sequence
scans, the rows still have to be read from disk and then ignored by the
engine. Vacuums also act as sequence scans, so the more data they're reading,
the longer that takes. This is especially true on an overloaded system.

I wouldn't be surprised if we end up doing a CLUSTER at some point.
The problem is basically that this machine is in 24/7 operation at
high-speed manufacturing plants, and the best-case scenario is for a
4-hour maintenance window.

The best case scenario is for them to buy a second server. If operation of
this app stack really is critical to business, they need to spend the money to
keep it working, or they'll end up paying much more for it when it fails. You
also said that server has other stuff running on it, and it already has very
little memory. That tells me they have no DR node. I'm afraid to even ask how
they're doing backups. That one machine is a giant, red, flashing single point
of failure. I really hope they understand that.

I've suggested that we might be able to help the situation somewhat
by attaching a portable USB-based hard disk, and adding a new
tablespace that'll let us keep running while we divide up the work
that the disk is doing, but they've made it clear that the current
hardware configuration cannot and will not change. Period.

And that's it, then. You have yourself a bad client. If it were me, I'd get
through this contract and never do business with them again. They have a
system that's basically 100% guaranteed to fail some time in the future (and
yet is critical for operation!) and are putting Band-Aids on it. I think
there's a parable somewhere about eggs and baskets, but I can't recall it at
this moment. ;)

There is more than one parable here.

For the client - don't be a damn fool. When you go to a doctor for a broken arm, you don't refuse the splint and insist on using just aspirin to manage the problem.

For the consultant/employee - stop buying into the bullshit. This is a common situation, where you tell your client, "You need X" and they refuse the advice. You need to be crystal clear with them that they are therefore NOT solving their problem.

I stopped giving in to the client's bullshit in this regard years ago when a customer tried to withhold over eight thousand dollars because I agreed to my manager's refusal to normalize a database and thus didn't fix a performance problem. I got paid when their programmer whom I'd secretly informed of the problem and how to fix it took over as the project manager, after using my advice to become the hero. The lesson I took is not to gloss over real problems because the client is recalcitrant. They don't win, you don't win, nobody wins. (Unless you use a workaround as I did, but politics is the court of last resort for an engineer.)

I'd rather have my bosses think I'm a little snarky (as long as I'm not fired for it), than have them hate me and try not to pay me. I am just loud about what is correct and what the consequences of incorrect are; then when they get those consequences I make sure to draw the connection.

I'm not there to make friends, I'm there to make solutions. It is fiduciary irresponsibility to let your clients go down in flames without at least informing them of the alternative.

--
Lew
Honi soit qui mal y pense.
http://upload.wikimedia.org/wikipedia/commons/c/cf/Friz.jpg

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