Re: PostgreSQL block size vs. LVM2 stripe width

Mark,

how often did you run your tests? Are the results reproduceable?

On Fri, 26 Mar 2004 14:00:01 -0800 (PST), markw(at)osdl(dot)org wrote:
> Linux-2.6.3, LVM2 Stripe Width
> (going across)
>PostgreSQL
>BLCKSZ
>(going down) 16 KB 32 KB 64 KB 128 KB 256 KB 512 KB
>2 KB 2617 2656 2652 2664 2667 2642
>4 KB 4393 4486 4577 4557 4511 4448
>8 KB 4337 4423 4471 4576 4111 3642
>16 KB 4412 4495 4532 4536 2985 2312
>32 KB 3705 3784 3886 3925 2936 2362

Unless someone can present at least an idea of a theory why a BLCKSZ of
8 KB is at a local minimum (1 or 2% below the neighbouring values) for
stripe widths up to 64 KB I'm not sure whether we can trust these
numbers.

Before I hit the send button, I did a quick check of the link you
provided. The links in the table contain the following test numbers:

16 KB 32 KB 64 KB 128 KB 256 KB 512 KB
2 KB 72 71 70 69 66 65
4 KB 64 63 62 61 60 58
8 KB 54 53 52 51 50 49
16 KB 79 78 77 76 75 74
32 KB 86 85 84 83 82 80

Does this mean that you first ran all test with 8 KB, then with 4, 2, 16
and 32 KB BLCKSZ? If so, I suspect that you are measuring the effects
of something different.

Servus
Manfred