Previous Next Contents

8. Questions Waiting for Answers

  1. Q: What are the option you have used for formating the (raid) disks? I used:
    mke2fs -b 4096 -R stride=4 ... blah
            
    
    or is it supposed to be 64K × 4 drives:
    mke2fs -b 4096 -R stride=262000 ... blah
            
    
    are there any other options ?
    stride blocks are filesystem blocks, not virtual memory pages. Is there a paper somewhere about what does the stride option do ? Also, in relation with the ``md'' device driver ? The stride option serves only one purpose: it tells mke2fs how many file system blocks will be written to each member in turn. This allows mke2fs to allocate the block and inode bitmaps so that they don't all end up on the same physical drive. I noticed last spring that one drive in a pair always had a larger I/O count, and tracked it down to the these meta-data blocks. Ted added the -R stride= option in response to my explanation and request for a workaround. > For a 4KB block file system, with stripe size 32KB, one would use -R > stride=8.
  2. Q: For testing the raw disk thru put... is there a character device for raw read/raw writes instead of /dev/sdaxx that we can use to measure performance on the raid drives?? is there a GUI based tool to use to watch the disk thru-put??


Previous Next Contents