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What happens with the data during a meta expansion using BCVs
I expanded metas several times now and it works great. During the symconfigure I tried watching the BCVs syncing back and forth, but I guess this is not exactly how the data flow goes.
Can anyone explain to me what happens to the data during the expansion ?
I'm using the folllowing syntax:
add dev 2D4C:2D51 to meta 16D0, protect_data=TRUE, bcv_meta_head=1655;
Furthermore I found out that you need 2-way-mir-BCVs for this, not RAID5 BCVs (Clones). Since I ran out of my RAID1 storage for use in the latest expansion, I was forced to use a few 500GB7k2 spindels, which weren't used yet instead of the 73GB15k spindels and I must say I didn't even notice a significant difference in the BCV establish and syncing process.
Can anyone explain to me what happens to the data during the expansion ?
I'm using the folllowing syntax:
add dev 2D4C:2D51 to meta 16D0, protect_data=TRUE, bcv_meta_head=1655;
Furthermore I found out that you need 2-way-mir-BCVs for this, not RAID5 BCVs (Clones). Since I ran out of my RAID1 storage for use in the latest expansion, I was forced to use a few 500GB7k2 spindels, which weren't used yet instead of the 73GB15k spindels and I must say I didn't even notice a significant difference in the BCV establish and syncing process.
rawstorage
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November 12th, 2007 06:00
RRR
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November 12th, 2007 06:00
I suspected the copy back from BCV to meta only to be needed when something goes wrong, because I couldn't see the copying back to the expanded meta taking place. So if I understand correctly, the BCV really is used and not just there for backup purposes ?
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November 12th, 2007 06:00
dynamox
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November 12th, 2007 06:00
the BCV that is used for protecting data, it needs to be the size of the meta being expanded, or the future capacity of the meta being expanded ?
Thanks
dynamox
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November 12th, 2007 06:00
mirror position on the STD, thus protecting you from
any data unavailable situation during the meta
expansion.
once the meta is expanded the BCV is released ?
RRR
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November 12th, 2007 06:00
So a 200GB RAID5 meta can be expanded using a 200GB 2-way-mir BCV. In fact: this is how we do it. We don't have RAID1 for production (I know, it's silly, but our customers are served by RAID5 only atm).
RRR
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November 12th, 2007 06:00
I have a pool of RAID1 storage just sitting there to be used for use in expansion changes. I configure it on a per case scenario with number of meta members and perhaps cylinder sizes etc etc
RRR
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rawstorage
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November 12th, 2007 06:00
rawstorage
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November 12th, 2007 06:00
rawstorage
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November 12th, 2007 06:00
Message was edited by:
PaulCork
dynamox
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RRR
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for Windows you do a rescan and you'll find out that the disk grew and the partition didn't. Use "diskpart" and select the right volume and type "expand" to have the partition expanded to the disk (lun) boundary.
On other OS's this might be different. Simply create a new partition or do a similar expand "trick".
rawstorage
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November 12th, 2007 06:00
A RAID5 BCV cannot be used for the expansion because it uses redirection technology (timefinder emulation) and the concepts behind the script require the moving mirror type of establish. Although a RAID5 BCV cannot be used a RAID5 STD can be expanded but you must use STANDARD-NON-RAID5 BCV device to be able to perform action.
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