Hi
after browsing various search results I'm not sure if a RAID0 (or a
RAID10) can be grown at all, especially as
https://raid.wiki.kernel.org/index.php/Growing
only mentions levels 1/4/5/6 while the mdadm man-page suggests raid0 but
not raid 10 - so consider me confused.
However, if at all possible, here is what I have/plan:
We have four 100GB SSDs partitioned only to use 50% of that, e.g.
parted -s /dev/sdc print
Model: ATA INTEL SSDSC2BA10 (scsi)
Disk /dev/sdc: 100GB
Sector size (logical/physical): 512B/512B
Partition Table: gpt
Number Start End Size File system Name Flags
1 2097kB 50.0GB 50.0GB primary raid
These are assembled like this:
# mdadm -D /dev/md0
/dev/md0:
Version : 1.2
Creation Time : Thu Oct 9 14:11:36 2014
Raid Level : raid10
Array Size : 97615616 (93.09 GiB 99.96 GB)
Used Dev Size : 48807808 (46.55 GiB 49.98 GB)
Raid Devices : 4
Total Devices : 4
Persistence : Superblock is persistent
Update Time : Tue Nov 25 10:18:33 2014
State : clean
Active Devices : 4
Working Devices : 4
Failed Devices : 0
Spare Devices : 0
Layout : far=2
Chunk Size : 64K
Name : einstein-db1.atlas.local:0
UUID : dcd28f40:a020f822:d87a5b91:31bedccf
Events : 38
Number Major Minor RaidDevice State
0 8 17 0 active sync /dev/sdb1
1 8 33 1 active sync /dev/sdc1
2 8 49 2 active sync /dev/sdd1
3 8 65 3 active sync /dev/sde1
But life always tells you your initial thoughts are wrong, so we would
like to expand this to use 75% of each SSD.
Without much thinking, I would simply follow the wiki page, mark a
device as failed, remove it, repartition it, add it again, and wait for
sync to complete. Repeat for all 4 devices and finally --grow with mdadm
(followed by xfs resizing) - and of course, all online, while machine is
in flight.
The question now is, will this really work with RAID10 or would one need
to change it to RAID0 first, then perform this exercise and convert back
to RAID10 afterwards (and possibly lose all data because I will
inadvertently will make a serious typo somewhere ;)).
cheers
Carsten
--
Dr. Carsten Aulbert - Max Planck Institute for Gravitational Physics
Callinstrasse 38, 30167 Hannover, Germany
phone/fax: +49 511 762-17185 / -17193
https://wiki.atlas.aei.uni-hannover.de/foswiki/bin/view/ATLAS/WebHome
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