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On Tuesday 09 February 2010 16:11:14 Stroller wrote: |
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> On 9 Feb 2010, at 13:57, J. Roeleveld wrote: |
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> > ... |
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> > With Raid (NOT striping) you can remove one disk, leaving the Raid- |
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> > array in a |
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> > reduced state. Then repartition the disk you removed, repartition |
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> > and then re- |
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> > add the disk to the array. |
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> |
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> Exactly. Except the partitions extend, in the same positions, across |
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> all the disks. |
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> |
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> You cannot remove one disk from the array and repartition it, because |
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> the partition is across the array, not the disk. The single disk, |
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> removed from a RAID 5 (specified by Paul Hartman) array does not |
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> contain any partitions, just one stripe of them. |
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> |
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> I apologise if I'm misunderstanding something here, or if your RAID |
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> works differently to mine. |
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> |
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> Stroller. |
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> |
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|
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Stroller, it is my understanding that you use hardware raid adapters? |
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If that is the case, then the mentioned method won't work for you and if your |
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raid-adapters already align everything properly, then you shouldn't notice any |
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problems with these drives. |
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It would, however, be interesting to know how hardware raid adapters handle |
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these 4KB sector-sizes. |
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|
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I believe Paul Hartman is, like me, using Linux Sofware raid (mdadm+kernel |
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drivers). |
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|
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In that case, you can do either of the following: |
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Put the whole disk into the RAID, eg: |
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mdadm --create --level=5 --devices=6 /dev/sd[abcdef] |
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Or, you create 1 or more partitions on the disk and use these, eg: |
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mdadm --create --level=5 --devices=6 /dev/sd[abcdef]1 |
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|
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To have linux auto-detect for raid devices work, as far as I know, the |
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partitioning method is required. |
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For that, I created a single full-disk partition on my drives: |
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-- |
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# fdisk -l -u /dev/sda |
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|
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Disk /dev/sda: 1500.3 GB, 1500301910016 bytes |
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255 heads, 63 sectors/track, 182401 cylinders, total 2930277168 sectors |
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Units = sectors of 1 * 512 = 512 bytes |
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Disk identifier: 0xda7d8d6d |
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|
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Device Boot Start End Blocks Id System |
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/dev/sda1 64 2930277167 1465138552 fd Linux raid autodetect |
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-- |
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|
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I, after reading this, redid the array with the partition starting at sector |
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64. Paul was unfortunate to have already filled his disks before this thread |
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appeared. |
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|
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The downside is: you loose one sector, but the advantage is a much improved |
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performance (Or more precisely, not incur the performance penalty from having |
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misaligned partitions) |
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|
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-- |
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Joost Roeleveld |
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