IS this true about RAID1

Soldato
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Raid 1 being as fast as raid 0??? as someone has said somewhere else?

Quote

"Not QUITE true... RAID1 can be just as fast as RAID0 for reading data, as it reads from both drives at once. Write performance in RAID1 is the same (actually, very slightly slower, but unnoticable on most machines) as a single drive as it has to write everything to both drives. I'd NEVER use RAID0 - just way too much chance to lose everything.

RAID5 is about the best to go for wherever possible though. You need a minimum of 3 disks, but it's a very fast, fault tolerant and industry standard setup."
 
RAID 1 mirrors data from one disk to another to provide hardware fault tolerance

RAID 0 splits all data into 'segments', the segment sizes are determined by the stripe size which is manually set when creating the array, this provides faster reads and writes, but if one drive fails you lose everything. Never store important files on a RAID 0 array unless you have a decent backup going.

RAID 5 will mirror data as well as stripe it, so you get performance and hardware fault tolerance.

RAID 1 - wiki said:
Increased read performance occurs when using a multi-threaded operating system that supports split seeks, very small performance reduction when writing.

http://en.wikipedia.org/wiki/RAID#Standard_levels
 
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Well implemented RAID1 could pretty much match RAID0's sequential read speed by striping reading between disks and in case of multithreaded reading of small files it can exceed speed of striped arrays by reading different files simultaneously from separate disks.
(in striped array file is rarely contained in one disk)


RAID 5 will mirror data as well as stripe it, so you get performance and hardware fault tolerance.
In read performance RAID5 is similar to RAID0 with one disk less in array. (one disk is taken by parity data)
But writing to RAID5 is slow because in addition to writing data there's need to calculate parity data which also needs to be saved.
And in case of small files (like installing software or game) writing can be very slow because doing single write operation can require two read operations before parity data can be calculated and written.
 
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