Partition block size different from device's and stacked LVM volumes ones


Apr 2, 2010
Hi 'moxers,

I have a pair of HP ML350 G6 servers with LSI MegaRAID 9266-4i+CacheVault driving Supermicro CSE836E16 enclosures via SAS bracket, filled with WD RE 3TB SATA drives. On these are configured a RAID10 array with one big virtual/logical drive with write caching and read-ahead enabled.

HDDs have 512B block size and VD strip size is 256KB. I have created a unique partition on the VD devices to use as a LVM PV. Then created three LVM LVs (in turn used as DRBD backing devices).

When I look at my setup using the blockdev command it shows a 4KB block size all around, except for the partition:

# blockdev --report /dev/sdb* /dev/dm-{3,4,5}
RO    RA   SSZ   BSZ   StartSec            Size   Device
rw   256   512  4096          0   6000069312512   /dev/sdb
rw   256   512   512       2048   6000068247040   /dev/sdb1
rw   256   512  4096          0   1000194703360   /dev/dm-3
rw   256   512  4096          0   1000194703360   /dev/dm-4
rw   256   512  4096          0     21474836480   /dev/dm-5

Putting aside that I'm hardly understanding why this is the case... does this may have a negative impact on storage performance ?

Thanks in advance


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