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Date:      Wed, 28 Mar 2001 10:22:59 +0930
From:      Greg Lehey <grog@lemis.com>
To:        Alfred Perlstein <bright@wintelcom.net>
Cc:        Brandon Gale <bgale@targetnet.com>, "Michael C . Wu" <keichii@peorth.iteration.net>, dillon@FreeBSD.ORG, fs@FreeBSD.ORG, hackers@FreeBSD.ORG
Subject:   Re: Vinum stripe size (was: tuning a VERY heavily (30.0) loaded server)
Message-ID:  <20010328102259.B92853@wantadilla.lemis.com>
In-Reply-To: <20010327163833.O9431@fw.wintelcom.net>; from bright@wintelcom.net on Tue, Mar 27, 2001 at 04:38:33PM -0800
References:  <20010327181141.H1161@wantadilla.lemis.com> <BBEFKIOENNNDEEHMOMHOKECIHCAA.brandon@targetnet.com> <20010328095143.N1161@wantadilla.lemis.com> <20010327163833.O9431@fw.wintelcom.net>

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On Tuesday, 27 March 2001 at 16:38:33 -0800, Alfred Perlstein wrote:
> * Greg Lehey <grog@lemis.com> [010327 16:21] wrote:
>> On Tuesday, 27 March 2001 at 17:59:23 -0500, Brandon Gale wrote:
>>>>> Do you think it'd be worth it to have vinum carp about what may
>>>>> be a non optimal stripe size?
>>>>>
>>>>>   "Warning N is probably a bad idea for a stripe size, see docs"
>>>>
>>>> Only if it can recognize the fact correctly.
>>>
>>> How about even having vinum recommend something?
>>
>> I'm open to code suggestions.  The problem is that by the time you
>> create it, it's too late.
>
> That's not true.

For a certain definition of "too late", maybe not.

> By the time you've newfs'd it, stored data on it and deployed it
> into production it's too late.

It's certainly later then.

> Right after you make the volume is a good time to print out a little
> banner telling them to check the docs, something like:
>
>   "WARNING: selecting a stripe size can be tricky, you really should
>    see the vinum(8) manpage specifically the section about FOO for
>    suggestions for optimal stripe sizes."

Yes, but then you've already selected your stripe size.  About the
best I can think of would be a utility function which calculates the
stripe size based on the number of subdisks, the total size and the
cylinder group size.  You could then do something like

 plex org striped

without the stripe size, and let vinum(8) decide the stripe size for
you.  As I said, code submissions welcome :-)

Greg
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