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Who is making the actual I/O?

4 posts in General Discussion Last posting was on 2009-12-17 19:36:35.0Z
Yaniv C. Posted on 2009-12-16 06:55:24.0Z
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From: Yaniv C.
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Subject: Who is making the actual I/O?
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Hi.
I am using ASE 15.0.2 and have question regarding I/O.
Which process(thread) in the ASE is respensible for the I/O?

If I have 10 different connections which make intensive
selects
is all 10 threads(SPID) are making the actual I/O or there
is other internal thread?

If the 10 SPIDs are making intensive insers, are all 10 SPID
are making I/O only to the transaction log
and only 1 single checkpoint thread is writing to the data
files?

Thanks,
Yaniv


Bret Halford Posted on 2009-12-16 17:03:50.0Z
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Yaniv C. wrote:
> Hi.
> I am using ASE 15.0.2 and have question regarding I/O.
> Which process(thread) in the ASE is respensible for the I/O?
>
> If I have 10 different connections which make intensive
> selects
> is all 10 threads(SPID) are making the actual I/O or there
> is other internal thread?
>
> If the 10 SPIDs are making intensive insers, are all 10 SPID
> are making I/O only to the transaction log
> and only 1 single checkpoint thread is writing to the data
> files?
>
> Thanks,
> Yaniv

In terms of reads, the 10 connections will make their own I/O
both as needed and predictively using the asynchronous
prefetch feature. They also write out their dirty log buffers
when transactions complete.

The checkpoint process is periodically writing both data and log
buffers. The housekeeper wash process will also be doing so
on an ongoing basis (depending on free cycles on the server).

User processes can also issue manual checkpoints using the
checkpoint command. DUMP, QUIESCE, and SHUTDOWN also issue
checkpoints.


ASTC HANDLER Posted on 2009-12-17 17:20:48.0Z
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From: ASTC HANDLER
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Subject: Re: Who is making the actual I/O?
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if you see spid with cmd = 'ASTC HANDLER' i think this will
do the async io's

> Hi.
> I am using ASE 15.0.2 and have question regarding I/O.
> Which process(thread) in the ASE is respensible for the
> I/O?
>
> If I have 10 different connections which make intensive
> selects
> is all 10 threads(SPID) are making the actual I/O or there
> is other internal thread?
>
> If the 10 SPIDs are making intensive insers, are all 10
> SPID are making I/O only to the transaction log
> and only 1 single checkpoint thread is writing to the data
> files?
>
> Thanks,
> Yaniv


Sherlock, Kevin [TeamSybase] Posted on 2009-12-17 19:36:35.0Z
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<ASTC HANDLER> wrote in message news:4b2a6870.5654.1681692777@sybase.com...
> if you see spid with cmd = 'ASTC HANDLER' i think this will
> do the async io's
>

No. that is a background process that manages transaction coordination
protocol when using CIS or distributed transactions. Nothing to do with
Async IO.

Disk IO is a queue which is managed by each ASE engine. ASE engines post
network io, disk io, as well as run other ASE internal and user tasks.
Hopefully, the newer ASE kernel design will refactor this architecture by
leveraging more advanced os and processor technology to effectively create
"thread pools" to service these kinds of operations.