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тАО08-05-2010 01:33 AM
тАО08-05-2010 01:33 AM
I believe the data is written within the EVA in the form of stripes on each disks. Does anyone know what is the stripe size, whether it is configurable, if yes - how to configure it?
Thanks
Ketan
Solved! Go to Solution.
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тАО08-05-2010 01:48 AM
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тАО08-05-2010 02:06 AM
тАО08-05-2010 02:06 AM
Re: Data Block size on EVAs
How are chunk size/stripe size/data chunks related? Is there a document with these details?
Ketan
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тАО08-05-2010 02:15 AM
тАО08-05-2010 02:15 AM
Re: Data Block size on EVAs
The stripe size defines how many chunks are included in that 'stripe'.
A 'data chunk' stores user data. P+Q chunks are used to store redundany information to be able to recover in case a disk holding a particular data chunk fails.
There is no single, official document (from HP) that describes this. A lot of this information can only obtained by training or discussion with people 'who know'.
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тАО08-05-2010 06:13 AM
тАО08-05-2010 06:13 AM
Re: Data Block size on EVAs
RAID0 - 1 Stripe (size 128KB) = 1 Chunk of 128KB
RAID1 - 1 Stripe (size 256KB) = 2 Chunks of 128KB chunks
RAID5 - 1 Stripe (size 640KB) = 5 Chunks of 128KB
RAID6 - 1 Stripe (size 768KB) = 6 Chunks of 128KB
Thanks
Ketan
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тАО08-05-2010 07:14 AM
тАО08-05-2010 07:14 AM
Re: Data Block size on EVAs
VRAID-0 - stripe size = 4 chunks
VRAID-1 - stripe size = 4 chunks
........ but chunks are mirrored, so physically there are 8 chunks in a stripe
VRAID-5 - stripe size = 5 chunks
........ 4 chunks store data and 1(one) stores redundancy information (P)
VRAID-6 - stripe size = 6 chunks
........ 4 chunks store data and 2(two) store redundancy information (P+Q)
You can mix different VRAID-levels in a disk group. A disk group need not have an amount of disk drives that is a multiple of the stripe size of a particular VRAID-level (e.e. VRAID-5: diskgroup need not have N*5 disk drives). Due to the way the EVA virtualization works, all VRAID-data is pretty equally striped across all disk drives in that disk group.
There is one exception due to the way VRAID-1 is implemented:
In a disk group with an odd (un-even) number of disk drives (e.g. 9, 11, 17, 111), one of the disk drives cannot store VRAID-1 data, because it is missing a 'partner'.
You may have seen documentation that suggests a disk group be N*8 disk drives - well, that is an optimization for VRAID-1. All 8 chunks of a stripe can be stored on 8 different disk drives.
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тАО08-05-2010 07:32 AM
тАО08-05-2010 07:32 AM
Re: Data Block size on EVAs
Anyway, many thanks for this information.
Ketan