What is the Zero detection in 3PAR

[binu_mathew]

Hi Experts,

Can any one explain me what is the zero detection in 3PAR . How ASIC chip perform this ?

The very basic doubt I have is How can ASIC chip detect Zero and remove it. As per my understanding data write in binary form like 100100. If Zero is removed from this ,then the value itself is changed and it is something else.

Or may be my undrrstaning of zero detection may be wrong

Appreciate comments form experts

[gregersenj]

Hi Mathew

It is explained in this document:

http://h20195.www2.hp.com/v2/GetPDF.aspx%2F4AA3-8987ENW.pdf

Basically, when the ASIC detect a 16 KiB block of pure zero's, it doesn't write the data (16 KiB zeroes) to the disks.

BR

/jag

[binu_mathew]

Hi,

Thanks for this document.

So The zero detection means the the white space reclamation. Which is done by ASIC chip with the help of softwar Thin persistance, Thin reclamation and Thin convertion.

Not that the zero detection from binaries  . Am I right ?

[Sheldon Smith]

Correct. As gregersenj wrote, when the node (ASIC) "sees" a 16KB page of all binary zero come in, it simply updates pointers and does not have to  physically write the zeros.

[binu_mathew]

Hi Smith,

Thanks for this answer.

How efficient this 16Kib block identification when compared to other storage vendor. I can understand that Since its taking only 16Kib block the IO operation required for this wil be less and increases the performance when compared to other storage vendor. But how about the eliminating Zero, or deduplication, when other are performing with the size of 4KB or 8 KB block size.

Can we change the value of 16Kib to a lesser one or a higher one

[Dennis Handly · Accepted solution]

>How efficient this 16KiB block identification when compared to other storage vendor.

Very, since it is done in the ASIC.

>Can we change the value of 16 KiB to a lesser one or a higher one?

No, not smaller unless the whole 16 KiB is zero for 32 of the 512 byte blocks.

But multiples of 16 KiB are obviously handled.

[CalvinZito]

Hi @binu_mathew,

I have a lot of HP 3PAR content on my blog that would help you better understand HP 3PAR. There are many things about the platform that are different from traditional, legacy disk arrays. I'm happy to answer any questions if you have them.

And apologies for taking so long to respond - I had intended to reply sooner but lost track of your post.