NeilBrown wrote:
On Tue, August 25, 2009 12:39 am, Simon Jackson wrote:I am trying to use write intent bitmaps on some RAID 1 volumes to reduce the rebuild times in the event of hard resets that cause the md driver to kick members out of my arrays. I used the mdadm --grow /dev/md0 --bitmap=internal and this appeared to succeed, but when I tried to examine the bitmap I get an error. :~$ sudo mdadm --grow /dev/md0 --bitmap=internal :~$ sudo mdadm -X /dev/md0 Filename : /dev/md0 Magic : 00000000 mdadm: invalid bitmap magic 0x0, the bitmap file appears to be corrupted Version : 0 mdadm: unknown bitmap version 0, either the bitmap file is corrupted or you need to upgrade your toolsQuoting from the man page: -X, --examine-bitmap Report information about a bitmap file. The argument is either an external bitmap file or an array component in case of an internal bitmap. Note that running this on an array device (e.g. /dev/md0) does not report the bitmap for that array. Particularly read the last sentence. Then try mdadm -X /dev/sda5
Well that's nice and clear, but raises the question "why not?" This would seem to be one of the most common things someone would do, to look at the bitmap for an array.
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