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Re: [linux-lvm] Max storage size per system



Stephan Austermuehle wrote:
> 
> Hello,
> 
> what is the absolut maximum storage capacity that can be managed on a
> single Linux 2.4 system with LVM?

man vgcreate
       -s, --physicalextentsize PhysicalExtentSize[kKmMgGtT]
              Sets  the physical extent size on physical volumes of this
volume group.
              A size suffix (k for kilobytes up  to  t  for  terabytes) 
is  optional,
              megabytes  is the default if no suffix is present.  Values
can be from 8
              KB to 16 GB in powers of 2. The default of 4 MB causes
maximum LV  sizes
              of  ~256GB because as many as ~64k extents are supported
per LV. In case
              larger maximum LV sizes are needed (later), you need to
set the PE  size
              to  a  larger value as well. Later changes of the PE size
in an existing
              VG are not supported.

So, this means you can allocate 
64k * 16G == 64*1024 * 16*1024*1024*1024 == 1125899906842624 bytes ==
1024Tera Bytes,

Hovever, 
       To limit kernel memory usage, there is a limit of 65536 physical 
extents  (PE)
       per  logical volume, so the PE size determines the maximum
logical volume size.
       The default PE size of 4MB limits a single logical volume to
256GB (see the  -s
       option  to raise that limit).  There is also (as of Linux 2.4) a
kernel limita­
       tion of 2TB per block device.

So, this would mean 2TB pr. LV, but there can also be a number of LV's.
I dont remember how many, but proberly a power of 2, like 256 or 64k. 
But wait, there is more...
You can have more than one VG system on your linux (no idea how many, i
have had 2)
So, all in all, i would asume you can have MANY TERABYTES. Possibly
Penta? bytes ?

How much space do you need anyway ?




JonB



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