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Re: RAID 0 risky ?


Rich Puhek schrieb:
> Thedore Knab wrote:
> >

> I'm not sure that there's significantly less work for RAID 0 than RAID
> 5. RAID 1 will definately have less reads on any particular drive than
> the other two (approzimately 50% will go to one disk, 50% to the other),
> but will have greater writes (100% of writes will affect both disks on
> RAID 1, it's possible some writes will not affect every disk on RAID 5,
> I think).

As far as I know every drive will have to write some data.

An example for RAID 5:

5 HDDs (everyony 30 GB)
you will have a "resulting" disk with 120 GB of usable data ((5-1) * 30)
30 GB of Data for Parity-Checking will be divided on every HDD.
(There is no complete Parity-Disk in RAID 5 - that's the difference to
RAID 4 which *is* using a special Parity-Disk)
If you write data, this data is divided on all hard-drives.
It is more secure than RAID 0 and less secure than RAID 1.

> Since you're looking at IMAP mail files, the data is probably
> critical... too critical to trust in a single drive failure. You're
> probably most concerned with read performance (since users will notice
> lag in reading email... deleting messages can plod away just fine,
> writing to the mail files is done by the MDA). Take a look at how much
> space you need, or are likely to need in the future. If you need a lot
> of space I'd go with RAID 5. If you want to really push the read
> performance, buy another drive and go RAID 1.
> I'd stay away from RAID 0 unless it's fairly non-critical data, and if
> you really need the throughput. An example I can think of would be
> something like a web cache.

Yeah, but if you need high-speed you could use RAID 0+1..

(First mirror your drives, than sripe them.
This is a bit more secure :-) )

> --Rich
> _________________________________________________________
> Rich Puhek
> ETN Systems Inc.
> _________________________________________________________


Sebastian Nerz

PS I hope the follwing links are okay:

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