Michael Evans wrote:
On Sun, Apr 18, 2010 at 8:46 PM, Kaushal Shriyan
<kaushalshriyan@xxxxxxxxx> wrote:
Hi
I am a newbie to RAID. is strip size and block size same. How is it
calculated. is it 64Kb by default. what should be the strip size ?
I have referred to
http://en.wikipedia.org/wiki/Raid5#RAID_5_parity_handling. How is
parity handled in case of RAID 5.
Please explain me with an example.
Thanks and Regards,
Kaushal
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You already have one good resource.
I wrote this a while ago, and the preface may answer some questions
you have about the terminology used.
http://wiki.tldp.org/LVM-on-RAID
However the question you're asking is more or less borderline
off-topic for this mailing list. If the linked information is
insufficient I suggest using the Wikipedia article's links to learn
more.
I have some recent experience with this gained the hard way, by looking
for a problem rather than curiousity. My experience with LVM on RAID is
that, at least for RAID-5, write performance sucks. I created two
partitions on each of three drives, and two raid-5 arrays using those
partitions. Same block size, same tuning for stripe-cache, etc. I
dropped an ext4 on on array, and LVM on the other, put ext4 on the LVM
drive, and copied 500GB to each. LVM had a 50% performance penalty, took
twice as long. Repeated with four drives (all I could spare) and found
that the speed right on an array was roughly 3x slower with LVM.
I did not look into it further, I know why the performance is bad, I
don't have the hardware to change things right now, so I live with it.
When I get back from a trip I will change that.
--
Bill Davidsen <davidsen@xxxxxxx>
"We can't solve today's problems by using the same thinking we
used in creating them." - Einstein
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