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I have existing RAID0 setup with two disks. I have to add a new drive to it. But when I try to run the following command:

mdadm --add /dev/md/customer_upload /dev/xvdl

I get an error:

mdadm: add new device failed for /dev/xvdl as 2: Invalid argument

How do I add a new disk to an existing RAID0?

I used the following steps to create RAID 0 initially:

 sudo mdadm --create --verbose /dev/md/customer_upload --level=stripe --raid-devices=2 device_name1 device_name2

EDIT

Seems like you cannot add disk to RAID0.

I ran the following command and it made it RAID4 How & Why I am still not clear

/dev/md/customer_upload --grow -l 0 --raid-devices=3 -a /dev/xvdl

I can see three disks in RAID4 but total space is still 2Tb

xvdf    202:80   0     1T  0 disk  
└─md127   9:127  0     2T  0 raid4 /customer_upload
xvdg    202:96   0     1T  0 disk  
└─md127   9:127  0     2T  0 raid4 /customer_upload
xvdl    202:176  0     1T  0 disk  
└─md127   9:127  0     2T  0 raid4 /customer_upload
MadHatter
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Ut xD
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3 Answers3

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yes you can, to add one disk to raid 0

mdadm --grow /dev/md0 --level=0 --raid-devices=3 --add /dev/sdd

or you can add several disks

mdadm --grow /dev/md0 --level=0 --raid-devices=4 --add /dev/sdd /dev/sde

raid-devices=4 total devices count with new disks, raid 0 become raid 4 and after reshape will be raid 0 again

and these sysctl opts for reshape speed control dev.raid.speed_limit_min and dev.raid.speed_limit_max

Андрей Кондратьев
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According to the kernel.org RAID wiki:

After the new disk was partitioned, the RAID level 1/4/5/6 array can be grown

that is, RAID-0 is not eligible for growing. You will need to backup all the data, recreate the array from scratch, and restore from backups.

MadHatter
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  • I did `mdadm /dev/md/customer_upload --grow -l 0 --raid-devices=3 -a /dev/xvdl` and it made my setup `RAID4`, I can see all the three disks attached using `lsblk` but total space is still 2Tb. How to resolve this? It should be 3Tb since each disk is of 1Tb – Ut xD Dec 04 '14 at 12:17
  • Firstly, are you sure it changed the RAID level? Can you cut-and-paste the output of `cat /proc/mdstat` into your question? Secondly, have you grown the FS to fill the device? You keep telling us you know things ("*total space is still 2Tb*") but you don't **show** us how you know them, which makes it difficult to comment. – MadHatter Dec 04 '14 at 12:23
  • added to question – Ut xD Dec 04 '14 at 12:28
  • A three-1TB-stripe RAID-4 should be 2TB usable (2 data 1 parity), which is what you say you see. You need this to be a 3-stripe RAID-0, and I still think that means you'll need to backup, nuke, recreate, and restore. – MadHatter Dec 04 '14 at 12:33
  • How much space would I require for parity in RAID5? – Ut xD Dec 04 '14 at 12:43
  • The same; the only difference is that the parity blocks are striped across all three drives in 5, as opposed to all on one disc in 4. – MadHatter Dec 04 '14 at 13:29
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Ok I searched about 20 different unsolved articles and I finally figured it out by dumb luck.

I had the same issue. I cloned the drive using sfdisk -d | sfdisk like the many manuals and blogs said. I later just opened fdisk /dev/sdd and then simply hit w to rewrite the partition table. This fixed my Invalid Argument error.

I hope this helps someone.

iwaseatenbyagrue
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Juzzy
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