well, I guess it should work, in theory. I just tried with loopback devices (1GB each). This is on Ubuntu Precise 12.04.1, kernel 3.2.0-35-generic. Got an OOPS, which triggered a panic (kernel.panic_on_oops = 1) which triggered a reboot (kernel.panic = 1). It might work, but not here - other RAID stuff works well on this box
See below for logs
roy
root@smilla:/raid/tmp/testraid# mdadm --create /dev/md1 --level=0 --chunk=256 --raid-devices=2 /dev/loop0 /dev/loop1
mdadm: Defaulting to version 1.2 metadata
mdadm: array /dev/md1 started.
root@smilla:/raid/tmp/testraid# cat /proc/mdstat
Personalities : [raid6] [raid5] [raid4] [linear] [multipath] [raid0] [raid1] [raid10]
md1 : active raid0 loop1[1] loop0[0]
2096640 blocks super 1.2 256k chunks
root@smilla:/raid/tmp/testraid# mkfs.xfs /dev/md1
...
(copy 200MB into the filesystem)
root@smilla:/mnt/raidtest# mdadm -G /dev/md1 --raid-disks=3 --add /dev/loop2
mdadm: level of /dev/md1 changed to raid4
mdadm: added /dev/loop2
mdadm: Need to backup 1536K of critical section..
mdadm: Cannot start reshape for /dev/md1
mdadm: aborting level change
root@smilla:/mnt/raidtest# Timeout, server 192.168.10.254 not responding.
seems like an OOPS was triggered
Dec 21 18:25:53 smilla kernel: [ 4742.265318] md/raid:md1: device loop1 operational as raid disk 1
Dec 21 18:25:53 smilla kernel: [ 4742.265321] md/raid:md1: device loop0 operational as raid disk 0
Dec 21 18:25:53 smilla kernel: [ 4742.265587] md/raid:md1: allocated 3228kB
Dec 21 18:25:53 smilla kernel: [ 4742.284092] md/raid:md1: raid level 4 active with 2 out of 3 devices, algorithm 5
Dec 21 18:25:53 smilla kernel: [ 4742.285250] RAID conf printout:
Dec 21 18:25:53 smilla kernel: [ 4742.285252] --- level:4 rd:3 wd:2
Dec 21 18:25:53 smilla kernel: [ 4742.285254] disk 0, o:1, dev:loop0
Dec 21 18:25:53 smilla kernel: [ 4742.285255] disk 1, o:1, dev:loop1
Dec 21 18:25:54 smilla kernel: [ 4742.987274] md: bind<loop2>
Dec 21 18:25:55 smilla kernel: [ 4743.426366] md/raid0:md1: bad disk number -1 - aborting!
Dec 21 18:25:55 smilla kernel: [ 4743.444444] md/raid0:md1: bad disk number -1 - aborting!
Dec 21 18:25:56 smilla kernel: [ 4743.451231] BUG: unable to handle kernel NULL pointer dereference at 0000000000000010
Dec 21 18:25:56 smilla kernel: [ 4743.452474] IP: [<ffffffffa0275369>] raid0_make_request+0x69/0x1c0 [raid0]
Dec 21 18:25:56 smilla kernel: [ 4743.453608] PGD 137668067 PUD 131424067 PMD 0
Dec 21 18:25:56 smilla kernel: [ 4743.454283] Oops: 0000 [#1] SMP
Dec 21 18:25:56 smilla kernel: [ 4743.454283] CPU 0
Dec 21 18:25:56 smilla kernel: [ 4743.454283] Modules linked in: xfs ebtable_nat ebtables ipt_MASQUERADE iptable_nat xt_CHECKSUM iptable_mangle kvm_amd kvm dm_crypt xt_hl ip6t_rt ib_iser rdma_cm nf_conntrack_ipv6 nf_defrag_ipv6 ib_cm iw_cm ib_sa ib_mad ib_core ipt_REJECT ib_addr iscsi_tcp libiscsi_tcp libiscsi scsi_transport_iscsi xt_limit xt_tcpudp xt_addrtype xt_state ip6table_filter ip6_tables nf_conntrack_netbios_ns nf_conntrack_broadcast nf_nat_ftp nf_nat nf_conntrack_ipv4 nf_defrag_ipv4 nf_conntrack_ftp nf_conntrack iptable_filter ip_tables x_tables snd_hda_codec_via snd_hda_intel snd_hda_codec snd_hwdep snd_pcm bridge stp snd_seq_midi snd_rawmidi snd_seq_midi_event arc4 snd_seq rt61pci crc_itu_t rt2x00pci rt2x00lib mac80211 snd_timer snd_seq_device cfg80211 eeprom_93cx6 sp5100_tco snd soundcore psmouse snd_page_alloc uvcvideo i2c_piix4 videodev v4l2_compat_ioctl32 serio_raw edac_core k10temp edac_mce_amd ext2 mac_hid w83627ehf hwmon_vid lp parport raid10 raid1 raid0 multipath linear btrfs zlib_deflate lib
Dec 21 18:25:56 smilla kernel: crc32c raid456 async_pq async_xor xor async_memcpy async_raid6_recov raid6_pq async_tx radeon ttm drm_kms_helper drm i2c_algo_bit sata_sil24 pata_atiixp usbhid hid r8169
Dec 21 18:25:56 smilla kernel: [ 4743.454283]
Dec 21 18:25:56 smilla kernel: [ 4743.454283] Pid: 16410, comm: blkid Not tainted 3.2.0-35-generic #55-Ubuntu To Be Filled By O.E.M. To Be Filled By O.E.M./M3A UCC
Dec 21 18:25:56 smilla kernel: [ 4743.454283] RIP: 0010:[<ffffffffa0275369>] [<ffffffffa0275369>] raid0_make_request+0x69/0x1c0 [raid0]
Dec 21 18:25:56 smilla kernel: [ 4743.454283] RSP: 0018:ffff8800be3918c8 EFLAGS: 00010202
Dec 21 18:25:56 smilla kernel: [ 4743.454283] RAX: 0000000000000001 RBX: ffff88002bcabc00 RCX: 0000000000000190
Dec 21 18:25:56 smilla kernel: [ 4743.454283] RDX: 0000000000000001 RSI: 0000000000000200 RDI: 0000000000000000
Dec 21 18:25:56 smilla kernel: [ 4743.454283] RBP: ffff8800be3918e8 R08: 0000000000000200 R09: 0000000000000100
Dec 21 18:25:56 smilla kernel: [ 4743.454283] R10: ffff8801877acf08 R11: 0000000000000000 R12: ffff88021f0566c0
Dec 21 18:25:56 smilla kernel: [ 4743.454283] R13: 0000000000000200 R14: 0000000000000000 R15: 0000000000001200
Dec 21 18:25:56 smilla kernel: [ 4743.454283] FS: 00007f4ed3929740(0000) GS:ffff88022fc00000(0000) knlGS:0000000000000000
Dec 21 18:25:56 smilla kernel: [ 4743.454283] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
Dec 21 18:25:56 smilla kernel: [ 4743.454283] CR2: 0000000000000010 CR3: 00000001014f4000 CR4: 00000000000006f0
Dec 21 18:25:56 smilla kernel: [ 4743.454283] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
Dec 21 18:25:56 smilla kernel: [ 4743.454283] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Dec 21 18:25:56 smilla kernel: [ 4743.454283] Process blkid (pid: 16410, threadinfo ffff8800be390000, task ffff88021dcddc00)
Dec 21 18:25:56 smilla kernel: [ 4743.454283] Stack:
Dec 21 18:25:56 smilla kernel: [ 4743.454283] 0000000000000001 0000000000000190 ffff88002bcabc00 ffff88021f0566c0
Dec 21 18:25:56 smilla kernel: [ 4743.454283] ffff8800be391948 ffffffff814e5cb0 0000000000011210 ffff8800be391968
Dec 21 18:25:56 smilla kernel: [ 4743.454283] ffff88021dcddc00 0000000000000010 ffff8800be391928 ffffffff8111b0a5
Dec 21 18:25:56 smilla kernel: [ 4743.454283] Call Trace:
Dec 21 18:25:56 smilla kernel: [ 4743.454283] [<ffffffff814e5cb0>] md_make_request+0xd0/0x200
Dec 21 18:25:56 smilla kernel: [ 4743.454283] [<ffffffff8111b0a5>] ? mempool_alloc_slab+0x15/0x20
Dec 21 18:25:56 smilla kernel: [ 4743.454283] [<ffffffff812f2044>] generic_make_request.part.50+0x74/0xb0
Dec 21 18:25:56 smilla kernel: [ 4743.454283] [<ffffffff812f2458>] generic_make_request+0x68/0x70
Dec 21 18:25:56 smilla kernel: [ 4743.454283] [<ffffffff812f24e5>] submit_bio+0x85/0x110
----- Opprinnelig melding -----
> All,
>
> I have yet to find THE definitive word (via any search and forums) if
> this is possible; expanding a raid0 set by adding drives. (Please, I
> know there is no redundancy, and that is fine as these volumes are
> really Amazon WS EBS volumes, so we only strip for speed improvements)
>
>
>
> It seem this works:
> more /proc/diskstats
> mdadm --create /dev/md0 --chunk=256 --level=0 --raid-devices=2
> /dev/sd[b-c]
> mdadm --detail /dev/md0
> mkfs.xfs /dev/md0
> mount /dev/md0 /mnt
> vi /mnt/test
> umount /dev/md0
>
> mdadm --grow /dev/md0 --level=0 --backup-file=/tmp/grow
> --raid-devices=3 --add /dev/sdd <= changes to raid4
> mdadm --detail /dev/md0
> mdadm --grow /dev/md0 --level=0 --backup-file=/tmp/grow <== changes to
> raid0
> mdadm --detail /dev/md0
>
> Can someone please confirm this correct and that raid0 can be
> expanded, or is there a better means to expand an raid0 raid set?
>
> Thanks!
> --
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--
Vennlige hilsener / Best regards
roy
--
Roy Sigurd Karlsbakk
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roy@xxxxxxxxxxxxx
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