Thanks for your answer, Phil.
On 14/10/16 13:53, Phil Turmel wrote:
On 10/14/2016 06:06 AM, Ramon Hofer wrote:
From what I was reading [1,2] it is useful for faster rebuilds.
But why is it not present for md[1234] as I used the same command to
create these RAIDs?
Is it only possible for the last of the linear devices, or is it only
used for almost empty devices, or was the bitmap introduced in a recent
update?
Bitmaps have been available for a long time, but including them on a new
array by default is recent. They are most useful if a device is
unexpectedly disconnected but otherwise OK. mdadm --re-add will allow
that device to rejoin the array and only the missing data (tracked by
the bitmap) will have to be written to sync it up.
What could be an unexpected disconnect? If a disc is accidentally
removed from a slot?
I wonder if I should and could add a bitmap for the other devices as well?
There is a performance hit, so it should be considered on a case by case
basis.
My uneducated guess would be that I don't really need it.
So I should probably remove the bitmap for the newly created device.
Although the performance hit is not really an issue in my case, I guess.
How much disk space is used for a 12 TB RAID5 bitmap?
Best regards,
Ramon
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