Hi again, all --
...and then davidtg-robot@xxxxxxxxxxxxxxx said...
%
% I have a 1T data drive (currently in use with data) that I'd like to
% mirror with a pair of 500G drives striped together. I'll be mirroring
% two partitions, and I'll be striping partitions to ensure the correct
[snip]
Is it OK to mirror a partition and an entire device? Are there any pros
or cons?
I now have my 2ea 500G drives partitioned
jpo:~ # parted /dev/sdc unit MiB print
Model: ATA WDC WD5000AAVS-0 (scsi)
Disk /dev/sdc: 476940MiB
Sector size (logical/physical): 512B/512B
Partition Table: gpt
Disk Flags:
Number Start End Size File system Name Flags
1 1.00MiB 472171MiB 472170MiB raid0-WD-WMASU0686160 raid
4 472171MiB 476940MiB 4769MiB reiserfs wwn-0x50014ee055b724ad
jpo:~ # parted /dev/sdd unit MiB print
Model: ATA WDC WD5000AAVS-0 (scsi)
Disk /dev/sdd: 476940MiB
Sector size (logical/physical): 512B/512B
Partition Table: gpt
Disk Flags:
Number Start End Size File system Name Flags
1 1.00MiB 472171MiB 472170MiB raid0-WD-WMASU0769665 raid
4 472171MiB 476940MiB 4769MiB ext3 wwn-0x50014ee055b72bcd
(I always reserve a small slice at the end of the disk in which to keep
array structure data and other helpful info) and striped
jpo:~ # mdadm --detail /dev/md0
/dev/md0:
Version : 1.2
Creation Time : Wed Mar 9 05:48:41 2022
Raid Level : raid0
Array Size : 966739968 (921.96 GiB 989.94 GB)
Raid Devices : 2
Total Devices : 2
Persistence : Superblock is persistent
Update Time : Wed Mar 9 05:48:41 2022
State : clean
Active Devices : 2
Working Devices : 2
Failed Devices : 0
Spare Devices : 0
Layout : -unknown-
Chunk Size : 512K
Consistency Policy : none
Name : jpo:500Graid0md (local to host jpo)
UUID : fc674dbd:577b7d48:5cbe936f:6954eb62
Events : 0
Number Major Minor RaidDevice State
0 8 33 0 active sync /dev/sdc1
1 8 49 1 active sync /dev/sdd1
into a 1T-ish device ready to be half a mirror. I had originally done
lots of partition size math equal exactly half of my 1T drive partition
jpo:~ # parted /dev/sdb unit MiB print
Model: ATA ST31000524AS (scsi)
Disk /dev/sdb: 953870MiB
Sector size (logical/physical): 512B/512B
Partition Table: gpt
Disk Flags:
Number Start End Size File system Name Flags
1 1.00MiB 858307MiB 858306MiB xfs pri
4 950055MiB 953869MiB 3814MiB pri
with existing data (and having to fudge around, not surprisingly, the
striping metadata overhead), and so I've been playing
jpo:~ # parted /dev/md0 unit MiB print
Model: Linux Software RAID Array (md)
Disk /dev/md0: 944082MiB
Sector size (logical/physical): 512B/512B
Partition Table: gpt
Disk Flags:
Number Start End Size File system Name Flags
1 1.00MiB 934641MiB 934640MiB 500Graid0md raid
4 934641MiB 944081MiB 9440MiB pri msftdata
with how to slice up the stripe device to size it to match the existing
sdb1 partition with the mirroring metadata overhead, when I wondered ...
do I care? I don't need the s4 slice on this virtual device; that's just
leftover space. I hate to think of it going to waste, but it's really
trivial in the grand scheme of things. Soooooo ... if it's just as happy
to mirror against a whole device as it is a slice of one, then maybe I
can skip ahead.
Thoughts?
Thanks again! :-)
:-D
--
David T-G
See http://justpickone.org/davidtg/email/
See http://justpickone.org/davidtg/tofu.txt
