Linux Raid Problem?

David Kinnvall david.kinnvall at alertir.com
Wed Oct 3 16:14:01 CDT 2001


Add one more to the list. 2550's with 4x10kRPM 18GB
drives as a single raid5 logical disk. Embarassingly
bad write performance, despite 128MB cache and battery.

I only *hope* it might prove to be a driver issue, but
then again, raid5 is probably not the optimal choice if
maximum write speed is the goal.

Has anobody got any numbers for the above hardware under
other supported OS's, like NT, Win2k or anything else?
If the performance there is as bad as under Linux, it
would seem likely to be a hardware issue, else it might
very well be a driver thing. Anybody?

Regards,

David

----- Original Message -----
From: "Chris Chabot" <chabotc at reviewboard.com>
To: "Hubbard, David" <dhubbard at dino.hostasaurus.com>; "'David Durham'"
<david.durham at wcom.com>; <Linux-PowerEdge at dell.com>
Sent: Wednesday, October 03, 2001 10:55 PM
Subject: Re: Linux Raid Problem?


> Actualy, i have been seeing some of these types of problems to on my
2550's,
> these are the newest 2u servers currently offers. The performance isn't as
> bad as you describe it, i get around 10mb/s write speed, and about
> 18-22Mb/sec read speed. This on a system _with_ a battery, and 4x 10krpm
> 18gig drives configured as a single raid 5 volume.
>
> As mentioned, a single 10krpm scsi u160 drive is able to get speeds higher
> then this.
>
>
> ----- Original Message -----
> From: "Hubbard, David" <dhubbard at dino.hostasaurus.com>
> To: "'David Durham'" <david.durham at wcom.com>; <Linux-PowerEdge at dell.com>
> Sent: Wednesday, October 03, 2001 10:32 PM
> Subject: RE: Linux Raid Problem?
>
>
> > No need to describe the problem Davy, it's a known issue
> > that raid performance on the 2400 sucks! :-)
> >
> > I have a bunch of 2400's running with the RAID controller
> > enabled with 10k rpm disks and I get a whopping 4.4 MB/s
> > write rate on it.  I can read at 10 to 15 times that rate.
> > The problem is that the garbage 2/Si raid controller on
> > our mother boards does not do write-back cache because it
> > does not support a battery backup and could not guarantee
> > the data.  I've still never heard a good explanation on
> > why we don't at least see a slightly better write rate
> > out of drives that can do 20 MB/s writes on their own,
> > the processor on the 2/Si must be garbage too.
> >
> > Sorry to be the bearer of bad news, I'm currently looking
> > to replace my 2400's with newer models, although this
> > issue pissed me off enough to consider other vendors, I'll
> > probably stay with Dell because their support is good,
> > especially from the Dell employees on this list.
> >
> > Dave
> >
> > > -----Original Message-----
> > > From: David Durham [mailto:david.durham at wcom.com]
> > > Sent: Wednesday, October 03, 2001 4:11 PM
> > > To: Linux-PowerEdge at dell.com
> > > Subject: Linux Raid Problem?
> > >
> > >
> > >   Before I describe this problem in more detail, can you tell
> > > me if you
> > > have ever heard of a problem with Linux and the PowerEdge 2400 series
> > > where the disk write speed is rediculusly slow around 3Meg/s
> > >   This is linux Mandrake 8.0 out of the box and I've
> > > configured via the
> > > BIOS, the 3 17 gig SCSI drives as a single 30 gig Raid 5 container.
> > >
> > > Thanks,
> > >    Davy
> > >
> > > _______________________________________________
> > > Linux-PowerEdge mailing list
> > > Linux-PowerEdge at dell.com
> > > http://lists.us.dell.com/mailman/listinfo/linux-poweredge
> > >
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> >
>
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