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Re: Hardware RAID vs. Software RAID

From: rob <robvl66_at_hotmail.com>
Date: Tue, 21 Oct 2003 08:47:58 +0200
Message-ID: <bn2kqv$qtj$1@news.tudelft.nl>

"Chuck Lucas" <chuck.lucas_at_mspb.gov> schreef in bericht news:bn15d0$5t7$1_at_ngspool-d02.news.aol.com...
> "Daniel Morgan" <damorgan_at_x.washington.edu> wrote in message
> news:1066587431.204277_at_yasure...
> > You are correct on all points.
> >
> > But what version you implement can make a big difference. I'd stay away
> > from RAID 5 and vendor RAID
> > implementations with numbers like 2 and 4.
>
> What's wrong with RAID 5?
>

I recently learned the following the hard way: Losing a disk means the data on that disk is reconstructed with the parity information. This means the system slows down considerably. - Batch jobs and backups take _much_ longer and exceed their normal timeframe.
- There is an extra load on all disks. In RAID 1 there is no extra disk load during the disk failure.
- Losing any another disk means : system down. In RAID 1 only the mirror of the broken disk is a single point of failure. - syncing a new disk puts a load on all disks instead of only the mirror of the broken disk in RAID 1+0
So RAID5 performance is not only an issue during normal operations. The performance during disk failure is so bad we can not guarantee our service levels.

Regards,
Rob Received on Tue Oct 21 2003 - 01:47:58 CDT

Original text of this message

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