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Date:      Wed, 3 Jan 2001 13:17:42 +1030
From:      Greg Lehey <grog@lemis.com>
To:        Zero Sum <count@shalimar.net.au>
Cc:        Alfred Perlstein <bright@wintelcom.net>, Thomas Seck <tmseck@web.de>, freebsd-stable@FreeBSD.ORG
Subject:   Re: Vinum safe to use for raid 0?
Message-ID:  <20010103131742.F15003@wantadilla.lemis.com>
In-Reply-To: <01010313305000.03936@shalimar.net.au>; from count@shalimar.net.au on Wed, Jan 03, 2001 at 01:30:50PM %2B1100
References:  <20010102230107.A559@basildon.homerun> <20010102152109.D19572@fw.wintelcom.net> <01010313305000.03936@shalimar.net.au>

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On Wednesday,  3 January 2001 at 13:30:50 +1100, Zero Sum wrote:
> On Wednesday 03 January 2001 10:21, Alfred Perlstein wrote:
>> * Thomas Seck <tmseck@web.de> [010102 14:00] wrote:
>>> Hi all,
>>>
>>> sorry if this is OT for -stable, but I followed the discussion about
>>> vinum in here and got a bit worried.
>>>
>>> I am currently deploying a proxy server for our company. It shall use
>>> squid on 4.2-STABLE. I would like to put the cache data on a vinum RAID
>>> 0, made of three U160 disks. As I understood the discussion so far,
>>> there are some unresolved problems with the raid 5 code. Could someone
>>> tell me whether I can safely use vinum for building a raid 0 system
>>> (despite the fact that the HW may be a point of failure of course)?
>>>
>>> Thanks in advance and best regards from Germany
>>
>> We've been using RAID-0 and RAID-1 with vinum here for a long time,
>> the only problem we had was during a 3.x->4.x upgrade, we were able
>> to recover from it after freaking out for a bit though.
>
> I know it is a bit off topic and if it has been discussed to death befire,
> I apologise.  But for the lfe of me I can't see why anyone would use RAID 5
> as other than an acadaemic exercise.
>
> If this seems like a troll, I'm sorry, but I have had this argument so many
> time in RL.  In the past I have always managed to get better performance by
> throwing RAID 5 out.

There are many reasons for using RAID.  If you're looking for good
read/write performance, you won't use RAID-5.  But if you have a web
server, for example, where 99% of all accesses are reads, then RAID-5
is quite a good choice.  I do tend to agree that a lot of people use
RAID-5 where RAID-1 would be a better choice.

>> So yes, it is stable.  I still wouldn't trust the RAID-5, but if
>> you want to get RAID-5 working you could take a shot on getting
>> some reproducable corruption/panics and let Greg know.
>>
> The lack of data may be because of it's lack of use as a general
> practice.

No, I don't think so.  I'm surprised to hear how many people use it.
I'm reasonably sure that the problems people have reported are due to
a bug in Vinum, but I suspect it needs something else in combination
in order to make it appear.  For a while there was a theory that you
need an fxp0 Ethernet card in the system, for example.

Greg
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