From: Phil Turmel <philip@turmel.org>
To: Ramon Hofer <ramonhofer@bluewin.ch>, linux-raid@vger.kernel.org
Subject: Re: "bitmap" line in /proc/mdstat
Date: Fri, 14 Oct 2016 07:53:02 -0400 [thread overview]
Message-ID: <8922e2e1-b612-fa32-6932-9f4158f52fe6@turmel.org> (raw)
In-Reply-To: <5800AE09.70608@bluewin.ch>
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.
> 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.
Phil
next prev parent reply other threads:[~2016-10-14 11:53 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-10-14 10:06 "bitmap" line in /proc/mdstat Ramon Hofer
2016-10-14 11:53 ` Phil Turmel [this message]
2016-10-14 12:32 ` Ramon Hofer
2016-10-14 13:59 ` Ramon Hofer
2016-10-14 14:10 ` Andreas Klauer
2016-10-14 14:23 ` Ramon Hofer
2016-10-14 16:08 ` Peter Sangas
2016-10-14 16:29 ` Ramon Hofer
2016-10-14 17:32 ` Peter Sangas
2016-10-14 17:38 ` Ramon Hofer
2016-10-14 17:43 ` Andreas Klauer
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