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ASE 15.5 IMDB vs ramdisk/tmpfs

3 posts in General Discussion Last posting was on 2010-06-01 09:48:40.0Z
Alberto Posted on 2010-05-31 16:54:17.0Z
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From: Alberto
Newsgroups: sybase.public.ase.general
Subject: ASE 15.5 IMDB vs ramdisk/tmpfs
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I'm investigating IMDB and have a question:

What are the benefits of IMDB vs ramdisk/tmpfs?

Ramdisk/tmpfs will survive a ASE restart (not a host
reboot).
'delayed commit' / cache binding could also be used with
ramdisk/tmpfs, but probably of limited benefit.

The IMDB option seems quite expensive vs free ramdisk/tmpfs.

Thanks for your feedback.


Michael Peppler [Team Sybase] Posted on 2010-06-01 04:40:51.0Z
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Subject: Re: ASE 15.5 IMDB vs ramdisk/tmpfs
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On Mon, 31 May 2010 09:54:17 -0700, Alberto wrote:

> I'm investigating IMDB and have a question:
>
> What are the benefits of IMDB vs ramdisk/tmpfs?
>
> Ramdisk/tmpfs will survive a ASE restart (not a host
> reboot).
> 'delayed commit' / cache binding could also be used with
> ramdisk/tmpfs, but probably of limited benefit.

A ramdisk implementation will still perform IO, meaning context switches
in ASE, handing over the request to the OS, etc, and will still require
logging and cache management. You will also need twice the memory (for the
ramdisk itself, and for the ASE data cache).

Michael


Alberto Posted on 2010-06-01 09:48:40.0Z
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From: Alberto
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Subject: Re: ASE 15.5 IMDB vs ramdisk/tmpfs
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> On Mon, 31 May 2010 09:54:17 -0700, Alberto wrote:
>
> > I'm investigating IMDB and have a question:
> >
> > What are the benefits of IMDB vs ramdisk/tmpfs?
> >
> > Ramdisk/tmpfs will survive a ASE restart (not a host
> > reboot).
> > 'delayed commit' / cache binding could also be used with
> > ramdisk/tmpfs, but probably of limited benefit.
>
> A ramdisk implementation will still perform IO, meaning
> context switches in ASE, handing over the request to the
> OS, etc, and will still require logging and cache
> management. You will also need twice the memory (for the
> ramdisk itself, and for the ASE data cache).
>
> Michael

Thanks for the info.
Not sure the difference in performance ramdisk vs IMDB will
be measurable.

In terms of the memory usage, the 2 implementations should
be about the same - i.e. you would reduce the ASE data cache
proportionally for a ramdisk.

The benefits of ramdisk/tmpfs are:
1) Less costly
2) DB is retained between ASE restarts

Benefits of IMDB
1) Faster (not sure if it's measurable)

Based on the cost of $19,995/CPU, it may be better to get an
SSD.

Thanks

Alberto