[GLLUG] Link two RAIDs in one LVM?

John Edwards john at cornerstonelinux.co.uk
Sun May 10 13:39:47 UTC 2020


On Sun, May 10, 2020 at 03:12:54PM +0200, Dr. Axel Stammler via GLLUG wrote:
> Hmm. How long would it take to copy (nearly) 8 TB? 

Depends a lot of the size and type of the data. If large video files
then those will copy fast, but if the files are all small or are hard
links then there is more metadata to update in the filesystem which
will longer.

A typical modern spinning disk SATA drive can do between about 100 and
160 MBytes/s for large files.

So a rough back of envelope calculation would be 8000000 / 100 / 3600
~= 22 hours. So I would expect this to be a job that would last a
couple of days.

> Obviously I would have to prevent any write access for that period of time.

In general a good idea, but it would depend on the nature of those
writes and how important the additional data is to you.

If they are altering existing files then probably yes, but if they
were just adding files then you could do several runs of 'rsync' to
complete the copy afterwards.

|    John Edwards   Email: john at cornerstonelinux.co.uk    |

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