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Date:      Tue, 26 May 1998 14:23:47 -0400 (EDT)
From:      Simon Shapiro <shimon@simon-shapiro.org>
To:        Charles Owens <owensc@enc.edu>
Cc:        Tom <tom@sdf.com>, freebsd-stable@FreeBSD.ORG, freebsd-scsi@FreeBSD.ORG, Raul Zighelboim <rzig@verio.net>
Subject:   RE: DPT install problem
Message-ID:  <XFMail.980526142347.shimon@simon-shapiro.org>
In-Reply-To: <Pine.BSF.3.95q.980526120346.26872B-100000@itsdsv2.enc.edu>

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On 26-May-98 Charles Owens wrote:
> On Tue, 26 May 1998, Simon Shapiro wrote:
> 
>> 
>> On 22-May-98 Raul Zighelboim wrote:
>> > 
>> > My 0.02 cents:
>> >       I did not installed FreeBSd on a DPT controller, but with an
>> > Adaptec controller.  Nevertheless, I have a DPT controller on a system
>> > with a large fs (71780140 1K blocks).  The system works, works well
>> > and
>> > has been up for 4 days as a very busy usenet news spool directory.
>> >       This is running 2.2-RELENG from last sunday.
>> 
>> This confirms my observations.  Thanx.
>> 
>> > As a sidebar; the DOS configuration software can only create arrays
>> > with
>> > up to 1 mbyte interleave.  Is this a limitation on the hardware or the
>> > software ?  Is (will there be) a way to create an array with a larger
>> > interleave (32 megs comes to mind).
>> 
>> An interleave factor larger than 1MB will be very inefficient:
>> 
>> a.  The SCSI bus will be used (locked) for long periods.  This will
>>     cause poor multi-tasking response.
>> 
>> b.  The cache memory will be able to contain very few stripes.
>> 
>> Also notice that in the context of FreeBSD, anything larger than 64K is
>> sort of mute, as the O/S limits all SCSI transfers to that size.  I do
>> not
>> know yet how CAM will do, but suspect it to be the same.
>> 
>> Ideally, stripe size should be such that the latency in setting up a
>> transfer + the latency in completeing a DPT-Host transfer are about
>> equal
>> to the time to transfer one block (the reality is a bit more complex
>> than
>> that);  In this manner, the DPT can continue to ``feed'' blocks to the
>> system (or the other way around) without pausing for disk.  This is why
>> a
>> multiple-bus equipped DPT can achive transfer rates that are limited by
>> the
>> PCI bus and/or the O/S.  This takes some careful tuning and
>> experimentation.
> 
> The setup I'm planning consists of 14 4.5GB UW (probably Seagate
> Cheetahs)
> drives split across two busses (using the DPT 3334UW/2).  If you don't
> mind, could you comment a bit further as to what this tuning would entail
> in my case?
> 
> The array will be at the heart of a file server cluster housing user and
> group home directories for 1300 or so users.
> 
> Also, how much cache RAM on the controller is practically useful?

Use the default stripe size (32k-64K).  When selecting drives, alternate
between the busses.  Use top quality cabling and termination.
Leave 1 drive as a hot spare.
Experiment with your application and stripe sizes (although for home
directories, anything 16K and above will work.
Try to split the array into several filesystems;  fsck on 50GB takes a
while.
AS much cache as possible.  Cannot have too much.
Play with the percentage of read-ahead and the percentage of dirty pages in
dptmgr.
Play with individual drives' cache parameters too.
Post the results (or at least send them to me).

Seriously consider using DPT drives, and DPT ECC memory, if possible, in
DPT cabinets.  You will get a much more reliable setup, with easier
maintenance.

Simon

> 
> Thanks,
> Charles
> 
>> > 
>> > ==================================================
>> > Raul Zighelboim                         rzig@verio.net
>> > 
>> >> -----Original Message-----
>> >> From:        Charles Owens [SMTP:owensc@enc.edu]
>> >> Sent:        Friday, May 22, 1998 2:43 PM
>> >> To:  Simon Shapiro
>> >> Cc:  Tom; freebsd-stable@FreeBSD.ORG; freebsd-scsi@FreeBSD.ORG
>> >> Subject:     RE: DPT install problem
>> >> 
>> >> On Fri, 22 May 1998, Simon Shapiro wrote:
>> >> 
>> >> > 
>> >> > On 21-May-98 Tom wrote:
>> >> > > 
>> >> > >   I'm trying to use the boot-dpt 2.2.6-RELEASE floppy to
>> >> > >   bootstrap
>> >> a new
>> >> > > DPT based system.  However, sysinstall hangs after newfs'ing the
>> >> > > filesystems.
>> >> > > 
>> >> > >   I'm using a 21GB array, with auto-defaults for the filesystems,
>> >> so /usr
>> >> > > is over 20GB in size.  If I delete /usr and replace it with a
>> >> 500MB
>> >> > > filesystem, leaving the remaining space unallocated, sysinstall
>> >> has no
>> >> > > problem completing the newfs step.
>> >> > > 
>> >> > >   Anyone else had problems with sysinstall on a mid-sized array
>> >> like
>> >> > > this?
>> >> > 
>> >> > Yup.  Me :-)
>> >> > But not on 3.0-current.  I noticed that 2.2 does not like huge
>> >> partitions,
>> >> > but this is not consnstent.
>> >> > 
>> >> > Simon
>> >> 
>> >> This has me a bit nervous.  This July I will be implementing an NFS
>> >> server
>> >> with a 60GB DTP-based array.  My plan has been to use 2.2-stable...
>> >> but
>> >> perhaps 3.0-current is my only choice?  Is this -stable problem
>> >> understood, with a fix coming any time soon?
>> >> 
>> >> Any other concerns that I should be sweating about as I'm planning on
>> >> building an array of this size?  (and it will probably double in size
>> >> the
>> >> following summer)
>> >> 
>> >> Thanks,
>> >> ---
>> >> ----------------------------------------------------------------------
>> >> ---
>> >>   Charles N. Owens                               Email:
>> >> owensc@enc.edu
>> >> 
>> >> http://www.enc.edu/~owensc
>> >>   Network & Systems Administrator
>> >>   Information Technology Services  "Outside of a dog, a book is a
>> >> man's
>> >>   Eastern Nazarene College         best friend.  Inside of a dog it's
>> >>                                    too dark to read." - Groucho Marx
>> >> ----------------------------------------------------------------------
>> >> ---
>> >> 
>> >> 
>> >> To Unsubscribe: send mail to majordomo@FreeBSD.org
>> >> with "unsubscribe freebsd-scsi" in the body of the message
>> 
>> ---
>> 
>> 
>> Sincerely Yours, 
>> 
>> Simon Shapiro                                          
>> Shimon@Simon-Shapiro.ORG
>>                                                         770.265.7340
>> 
> 
> ---
> -------------------------------------------------------------------------
>   Charles N. Owens                               Email:  owensc@enc.edu
>                                              http://www.enc.edu/~owensc
>   Network & Systems Administrator
>   Information Technology Services  "Outside of a dog, a book is a man's
>   Eastern Nazarene College         best friend.  Inside of a dog it's 
>                                    too dark to read." - Groucho Marx
> -------------------------------------------------------------------------
> 
> 

---


Sincerely Yours, 

Simon Shapiro                                           Shimon@Simon-Shapiro.ORG
                                                        770.265.7340

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