> Has anyone done any benchmarking work on ccd interleaves to determine
> which ones are better and worse? I notice that the ccdconfig manual
> page gives 16 as an example interleave, but I've found that powers
> of two tend to concentrate inode activity on one drive (I've seen
> cases where I untar a file and one drive in the ccd is quite active
> while the other is virtually idle). I've been using 96, (which is
> about 20% faster than 32 when untarring a large directory tree with
> a lot of small files in it), but haven't really done a lot of
> experimentation yet to see if perhaps prime interleaves or something
> like that would be more optimal.
> 

Oddly enough, yes.

>From owner-storage-devel@nas.nasa.gov  Thu Oct 16 13:14:57 1997
Date: Thu, 16 Oct 1997 13:21:04 -0700 (PDT)
From: Matthew Mjacob <mjacob@nas.nasa.gov>
To: storage-devel@nas.nasa.gov
Subject: proper interleave for CCD devices and relative FFS or other blocksizes
Content-Length: 4185
Status: RO


Below is some tests with different interleaves and blocksizes for a 4 channel
raw read of the MegaDrive arrays.

There are some counterintuitive patterns here. For example, the best overall
rate is 128 interleave and 256K blocksizes. However, the best likely file
system block size read rate (at 64k) is for a 32 interleave.

Alan- do you think you could try and sanity check this on fineleg?
The script I'm using is in my home directory on jules, and there's
a copy of lmdd in my home directory on fineleg.

-matt

Script started on Thu Oct 16 13:00:56 1997
jules.nas.nasa.gov > root ccd0_ileave_test.sh
=========================================================================
Interleaving Read Test on machine  jules.nas.nasa.gov
Run on: Thu Oct 16 13:00:58 PDT 1997
For disks in ccd0  <-  /dev/sd5d /dev/sd7d /dev/sd9d /dev/sd11d.
Interleave is 2
        BlockSize is 32k:       78.12 MB in 5.80 seconds (13.4771 MB/sec)
        BlockSize is 64k:       78.12 MB in 5.41 seconds (14.4508 MB/sec)
        BlockSize is 128k:      78.12 MB in 5.41 seconds (14.4456 MB/sec)
        BlockSize is 256k:      78.00 MB in 5.65 seconds (13.7948 MB/sec)
--------------------------------------------------
Interleave is 4
        BlockSize is 32k:       78.12 MB in 3.40 seconds (23.0017 MB/sec)
        BlockSize is 64k:       78.12 MB in 3.12 seconds (25.0704 MB/sec)
        BlockSize is 128k:      78.12 MB in 2.94 seconds (26.5515 MB/sec)
        BlockSize is 256k:      78.00 MB in 2.89 seconds (26.9473 MB/sec)
--------------------------------------------------
Interleave is 8
        BlockSize is 32k:       78.12 MB in 2.44 seconds (32.0769 MB/sec)
        BlockSize is 64k:       78.12 MB in 2.06 seconds (37.9146 MB/sec)
        BlockSize is 128k:      78.12 MB in 1.89 seconds (41.3650 MB/sec)
        BlockSize is 256k:      78.00 MB in 1.80 seconds (43.2674 MB/sec)
--------------------------------------------------
Interleave is 16
        BlockSize is 32k:       78.12 MB in 1.86 seconds (42.0167 MB/sec)
        BlockSize is 64k:       78.12 MB in 1.50 seconds (52.1169 MB/sec)
        BlockSize is 128k:      78.12 MB in 1.31 seconds (59.5236 MB/sec)
        BlockSize is 256k:      78.00 MB in 1.23 seconds (63.1896 MB/sec)
--------------------------------------------------
Interleave is 32
        BlockSize is 32k:       78.12 MB in 2.32 seconds (33.7126 MB/sec)
        BlockSize is 64k:       78.12 MB in 1.25 seconds (62.5977 MB/sec)
        BlockSize is 128k:      78.12 MB in 1.06 seconds (73.5291 MB/sec)
        BlockSize is 256k:      78.00 MB in 0.97 seconds (80.1121 MB/sec)
--------------------------------------------------
Interleave is 64
        BlockSize is 32k:       78.12 MB in 3.30 seconds (23.6476 MB/sec)
        BlockSize is 64k:       78.12 MB in 1.71 seconds (45.6620 MB/sec)
        BlockSize is 128k:      78.12 MB in 0.93 seconds (84.2988 MB/sec)
        BlockSize is 256k:      78.00 MB in 0.83 seconds (93.8560 MB/sec)
--------------------------------------------------
Interleave is 128
        BlockSize is 32k:       78.12 MB in 3.31 seconds (23.6337 MB/sec)
        BlockSize is 64k:       78.12 MB in 2.73 seconds (28.5918 MB/sec)
        BlockSize is 128k:      78.12 MB in 1.41 seconds (55.4016 MB/sec)
        BlockSize is 256k:      78.00 MB in 0.77 seconds (101.3596 MB/sec)
--------------------------------------------------
Interleave is 256
        BlockSize is 32k:       78.12 MB in 3.30 seconds (23.6756 MB/sec)
        BlockSize is 64k:       78.12 MB in 2.74 seconds (28.5510 MB/sec)
        BlockSize is 128k:      78.12 MB in 2.45 seconds (31.9106 MB/sec)
        BlockSize is 256k:      78.00 MB in 1.26 seconds (61.9162 MB/sec)
--------------------------------------------------
Interleave is 512
        BlockSize is 32k:       78.12 MB in 3.32 seconds (23.5571 MB/sec)
        BlockSize is 64k:       78.12 MB in 2.74 seconds (28.5408 MB/sec)
        BlockSize is 128k:      78.12 MB in 2.46 seconds (31.7586 MB/sec)
        BlockSize is 256k:      78.00 MB in 2.31 seconds (33.8154 MB/sec)
--------------------------------------------------
jules.nas.nasa.gov > exit
exit

Script done on Thu Oct 16 13:02:40 1997