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Re: [HELP] RAID chunk-size - alternatives

hi ya russell

On Tue, 2 Apr 2002, Russell Coker wrote:

> On Tue, 2 Apr 2002 13:48, Alvin Oga wrote:
> > chunk size does NOT matter for raid5...
> Chunk size does not matter for RAID-1, but does matter for other RAID levels.

humm ..thought was the otehr way ... time for me to go look at some
raid source code i suppose .. when time permits

> > if your disk was partitioned as... 2K bytes/inode...
> You probably mean 2K blocks.  The number of bytes per inode just determines 
> the size of the inode tables.

yuppers ... and a block is 512bytes ( aka a sector ) 
and 63 sectors per track (aka cylinder)
and number of cylinders give you the size-of-your-disk


> > it also makes a difference if you used a inode size of 1K or 2K or 4k
> > during disk partitioning
> > 	- lots of little files or  few huge/gigantic files  ??
> If you have lots of little files then if you want good write performance then 
> you want RAID-1 or RAID-10.  RAID-5 is the cheap alternative.

hummm ..... thinking outloud....

"cheap" is relative???
	- $$$ for disks vs "(usable) disk space lost to raid"

typically a minimum of 2 disks used for raid0 or raid1...
	raid1(mirroring) protects against one disk failure
	( one disk's capacity is used as a redundant copy and not for user)
		( 50% lost of space )

	raid0(stripping) does not help for disk failures

typically 5 disks for raid5 ... 
	( 3 disks mininum -- 1/3 of your disks lost to parity
	( 4 disks .......... 1/4 of your disks lost to parity
	( 5 disks .......... 1/5 of your disks lost to parity

typically raid01 - needs 4 disks ...
	first data is stripped across 2 disks than its mirrored to 2 more disks
	- due to mirroring... 2 disks is lost for "mirror"

and after its all said and done... pull out a disk (simulated disk crash)
and see if you're data is still intact

c ya

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