How is wide striping done in DP ? Is data striped across all the DP Pool Vols???? If I create a 50Mb Lun will it reside on all the thick ldevs which makes up the pool?
For VSP the data in an HDP pool is always distributed in pages across all disks in the pool. A 50 MB LUN is very small, and as a result it will not be striped across much. Each 42Mb page will live on a single RG. So it will use at most 2 RG of the pool.
When you create a DP pool from the RAID Group, that is divided into 42MB pages and will be used On-Demand. A LDEV/LUN is wide striped using 42 MB page multiples, so this uses the disk spindles across the DP pool.
I hope this gives some clarification.
^^^^ this is what the theory says but my query is ____ If I create a 50Mb Lun will it reside on all the thick ldevs which makes up the pool?
HDP/HDT allocates space in 42MB pages. Each page is allocated only on first write and each 42MB page represents a single continuous area on a selected DP-VOL (phisical, thick vol). Pages are rebalanced on pool/tier expansion/shrink or on a zero reclaim operation.
Each DP-VOL belongs to a single parity group, RAID-1/5/6, 4/8 disks.
If you have a 50MB VVOL (in fact, that's a suboptimal choice, 50MB VVOL will use 100MB), it covers two pages max, so, it will use two PG max.
If you have a 2TB VVOL with only two pages allocated, it will also use two PG.
I just want to make sure what HDS storage system you are asking about. If it is the HUS 110, 130 or 150, I will ( slightly ) revise some of the answers.
Sorry, I assumed VSP
ThNks..... My query was for VSP only. I understand that storage is allocated in 42MB Chunks that is for thin allocation.....
But what is the stripe size VSP uses internally to write data across all thick ldevs within a pool?
The stripe size used by VSP is 512 KB chunks. (VSP uses two 256KB chunks from the same disk before moving to the next disk.)
If you have RAID 5 of 7D+1P, then the stripes will be calculated as 7* 512.
Please point me towards some PDFs related to this ^^^^
Unfortunately I don't have a document for this.
let me know from which website you got this info.....i want more details
After browsing through all the documents, I have found the same in the architecture guide in page 35. Here is the link for that.
The answer depends on what Storage Array. Is it HUS-1XXX, HUS-VM, VSP, or something else.
Am asking for vsp
I understood that a 42MB page is allocated at a time from a single PG which is striped twice across 7 disks of that PG (raid 5) with stripe unit of 256KB.
Plzzz correct me if am wrong.
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