Topic: E-Smith and Striping

[Neal Nagata, Jr.]

Hello,

I am running E-Smith on a   850 MB drive and i have just commited this drive for a trade. I've got a raid rack with 4 3 gig drives in it doing nothing. So I am going to have to move E-smith over to the scsi drives... The question is, Does E-Smith support Striping?

Thanks

Neal

[Gordon Rowell]

Neal Nagata, Jr. wrote:
>
> Hello,
>
> I am running E-Smith on a   850 MB drive and i have just
> commited this drive for a trade. I've got a raid rack with 4
> 3 gig drives in it doing nothing. So I am going to have to
> move E-smith over to the scsi drives... The question is, Does
> E-Smith support Striping?

Mirroring yes, striping no.

We don't ever plan to support RAID0 or software RAID5. We may look at mirrored stripes at a later stage, but we only support plain mirrors at this stage.

Gordon

[Darrell May]

Neal Nagata, Jr. wrote:
>
> Hello,
>
> I am running E-Smith on a   850 MB drive and i have just
> commited this drive for a trade. I've got a raid rack with 4
> 3 gig drives in it doing nothing. So I am going to have to
> move E-smith over to the scsi drives... The question is, Does
> E-Smith support Striping?
>
> Thanks
>
> Neal

Supports software RAID 1.  For hardware RAID check for RedHat 7.0 compatibility.

Darrell

[Stephan Goeldi]

> We don't ever plan to support ..... RAID5

Why not? Is there a big difference in supporting RAID1 or RAID5?

[Gordon Rowell]

Stephan Goeldi wrote:
> > [Gordon Rowell]
> > We don't ever plan to support ..... [software] RAID5
>
> Why not? Is there a big difference in supporting RAID1 or
> RAID5?

To quote Peter Green from the devinfo list:
    Only use RAID0 when your data is worthless. Only use RAID5    (software) when your CPU/performance is worthless.

RAID5 is a performance killer. It turns nice fast disks into very slow ones. It is a great idea when you have a cache between your system and the disks, but a very bad idea if your system has to monitor every read/modify/write cycle.

The system overhead of mirroring is less than 10%, and in fact may improve throughput in some circumstances. The overhead of RAID5 is more like 30-35% and gets far worse as the write ratio increases.

Gordon

[Stephan Goeldi]

> RAID5 is a performance killer.

Interesting aspect. So you think http://www.goeldi.com/e could be faster without RAID5?

[guestFF]

Hold your horses everyone,

This thread is off topic regarding e-smith. Why?????????

Because it is a matter of what kind of raid mechanisme is used, software or hardware????

E-smith obvisously is a software product and therefor Gordon's reply is correct. Add the fact that e-smith is intended for a 'out of the box solution' adding mirroring is a good thing. Here on dev forum we sometimes forget the 'motive' of the product.....

All other raids are depending on .....................................whatever your hardware is or you want your config to look like.

If you want raid5 'out of the box' buy a hardware controller with processor, dual channel, fast bus etc. etc. otherwise, let's talk about 'real' issues that concern e-smith, wich is a 'tailer made' ditribution. Athough based on RH7 it doesn;'t mean it has to do all the 'possible trickes'

Regards,

HFW

[Dan Brown]

First, no, it isn't off-topic for e-smith.  e-smith already includes mirroring; there's no inherent reason that it couldn't do software RAID 5 (though there are plenty of good practical reasons).

Second, this isn't the dev forum; that would be the devinfo mailing list.

[guestFF]

You're right Dan, i responded badly. Sorry.