Thread (21 messages) 21 messages, 6 authors, 2011-05-20

Re: Best way to create RAID-6 for swap partition - existing one failed

From: Stan Hoeppner <hidden>
Date: 2011-05-18 21:53:39

On 5/18/2011 3:13 PM, Gavin Flower wrote:
quoted hunk ↗ jump to hunk
--- On Thu, 19/5/11, Stan Hoeppner <stan@hardwarefreak.com> wrote:
quoted
From: Stan Hoeppner <redacted>
Subject: Re: Best way to create RAID-6 for swap partition - existing one failed
To: "Gavin Flower" <redacted>
Cc: linux-raid@vger.kernel.org, neilb@suse.de, mb@gem.win.co.nz
Date: Thursday, 19 May, 2011, 6:59
On 5/16/2011 4:41 PM, Gavin Flower
wrote:
quoted
Motivation, existing RAID-6 swap partition
failed.  I am thinking I should recreate it in a new
format, as currently it is 'Version : 0.90', rather than
simply rebuild it.
<snip>

Forget using a partition.  Simply use a swap
file.  This example creates
a 1GB swap file in the / filesystem.  You can locate
it on any
filesystem you wish.

# swappoff -a
# dd if=/dev/zero of=/swapfile1 bs=1024 count=1048576
# mkswap /swapfile1
# swapon /swapfile1
# vi /etc/fstab
Add:
/swapfile1 swap swap defaults 0 0

and remove your old entry for the failed swap partition.

There is little performance difference between swap files
and swap
partitions with modern kernels.  The kernel will map
the disk location
of the swap file and perform direct disk access, bypassing
the
filesystem and buffer cache.

-- 
Stan
Thanks.

Interesting!

(Reminds me of when I first got into Linux.  Then you could have any size swap file up to 128 MB, and have up to 8 swap files, for a maximum of 1 GB. I then had about 64 MB of RAM - now I have 8 GB of RAM. Also, swap partitions were recommended.  When the 2.4 kernel first came out, it was said to be faster if you had at least 16 MB.)

I read up and could not see any benefit in changing, so I ended up 'simply' reassembling the partition.
The big benefits are flexibility, simplicity, and time consumed.  Given
your particular case it seems a bit ironic that you see no benefit in
using swap files.  The time to resolution in this case would be mere
seconds with swap files.  How much total time did you spend reassembling
your swap partition, bot command execution time, but your total time?

-- 
Stan
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