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*From*: Andrew Patterson <andrew lvadp fc hp com>*To*: linux-lvm sistina com*Subject*: [linux-lvm] What is the the maximum logical volume size?*Date*: Wed, 11 Apr 2001 15:58:09 -0600

I am tring to figure out what the maximum logical volume size is. The vgcreate man page says: 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. There is also (as of Linux 2.4) a kernel limitation of 2TB per block device. Which implies that the limit is 2 TB on my 2.4 system. However in tools/lib/lvm.h for version 0.9.1_beta7, it states: /* * LVM_PE_T_MAX corresponds to: * * 8KB PE size can map a ~512 MB logical volume at the cost of 1MB memory, * * 128MB PE size can map a 8TB logical volume at the same cost of memory. * * Default PE size of 4 MB gives a maximum logical volume size of 256 GB. * * Maximum PE size of 16GB gives a maximum logical volume size of 1024 TB. * * AFAIK, the actual kernels limit this to 1 TB. * * Should be a sufficient spectrum ;*) */ Which tells me it is 1 TB. In the same file: #define LVM_LV_SIZE_MAX(a) ( ( long long) LVM_PE_T_MAX * (a)->pe_size > ( l ong long) 1024*1024/SECTOR_SIZE*1024*1024 ? \ ( long long) 1024*1024/SECTOR_SIZE*1024*1024 : \ ( long long) LVM_PE_T_MAX * (a)->pe_size) Which says we can have at most 1024*1024/SECTOR_SIZE*1024*1024 or 2GBs of sectors or blocks?. vg_show.c used in vgdisplay then converts this value with the call: ( LVM_LV_SIZE_MAX(vg) / 2, SHORT); vgdisplay then shows this as 1 TB (assuming you have a large enough extent size). So I am not sure whether there is an incorrect calculation in the define, an incorrect calculation in vg_show.c, or if the man page is incorrect and the kernel limit is actually 1 TB. If the man page is wrong, why only 1 TB. 1 >> 32 * (512 sector size) should give 2 TB's. Andrew Patterson

**Follow-Ups**:**Re: [linux-lvm] What is the the maximum logical volume size?***From:*Andreas Dilger