From: Alexander Gonta 
Subject: Re: Probs with Mylex Raid-Controller
Date: 1998/05/11
Message-ID: #1/1
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Reply-To: agonta@ix.netcom.com
To: Wolfram Seidel 
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Organization: Netcom
Newsgroups: fido.novell


Hi Wolfram,

I suggest you use all 9 drivers in the array, not separate Logical drives
with 3 drives per logical drive. More read/write heads in array
will improve performance. In addition, with more drives in
single array, each drive become 1/9 th of total disk space,or 11%
and thus, it's rebuild speed is fast, since percentage of total disk space
is only a small percentage of total capacity. But with 1/3 of an
"array" or a sub array, a logical drive that is being rebuild
is a significant percentage of total space, 33%, and per logical
drive!. My recommendation, rebuild whole thing and do a tape
restore.

                        Hope I've helped.

                                    Sincerely,

                                   Alex G.


Wolfram Seidel wrote:

> Hi,
>
> I've got a Server system with the following configuration:
>
> PPro 200, 512MB, Mylex DAC960 Raid Controller, 9 Disc-Drives (all Seagate
> 9GB). Currently they are configured as 3 Disc Packs with 3 drives each (RAID
> 5); OS is Netware 4.11
>
> Problem #1:
> When a drive is being rebuild (i have simulated this by disconnecting a drive
> and reconnecting it later) the performance of the array drops to less than
> 1/30 of the original performance... this means, it is NOT possible to work
> seriously with the server until the rebuild is finished. There exists a
> parameter "Rebuild rate" which -according to the manual- sets the priority of
> the rebuild process... but even on the  lowest setting "0" the speed of the
> array is not acceptable.
> However we have about 100 Users which need to work on the server... even if a
> drive fails. (that is why we bought the raid system in the first place).
>
> Is there any solution to this? I dont care if the rebuild process takes a long
> time but the server must be usable during this time.
>
> #2: Is it a good idea to configure the drives as we did? (3 packs with 3
> drives each) or would other possibilities be better? Our first consideration
> is security, not speed.  What about one pack with 8 drives (or two with 4) and
> one as a standby drive? Would a different configuration perhaps help solving
> my problem?
>
> #3: If I down the server, disconnect one harddisk and switch it on again, the
> Mylex BIOS refuses to configure the array... thus the system disk is
> unavailable. I have to boot from floppy disk, start the Config-Program and
> manually save the new configuration (one dead disk)... then reboot and then
> the system drive will be available (in state "critical").
> Is there no way to let the controller do this automatically?
>
> If you know any answers to these questions....  I'd be happy
>
> Yours
> Wolfram
>
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