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graysky
PostPosted: Sun Jul 20, 2008 10:20 am 
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Joined: Wed Dec 10, 2003 8:31 pm
Posts: 1996
Location: /dev/null
After learning about these utils to measure fragmentation and defrag it on XFS based filesystems, I noticed that when I copy files over from my dvdrom (or through samba), to my /myth (which is XFS), they contain huge amount of fragments.... is this normal? Can anyone else running xfs confirm?

Here I queried a file ~1 gig in size that I just copied over via Samba (similar results obtained using the local dvdrom on the LINUX box):

Code:
# xfs_bmap -v 18-Jun-2007.mkv
18-Jun-2007.mkv:
 EXT: FILE-OFFSET         BLOCK-RANGE        AG AG-OFFSET            TOTAL
   0: [0..9503]:          67181048..67190551  0 (67181048..67190551)  9504
   1: [9504..25887]:      63597504..63613887  0 (63597504..63613887) 16384
   2: [25888..58655]:     58657216..58689983  0 (58657216..58689983) 32768
   3: [58656..99615]:     46611680..46652639  0 (46611680..46652639) 40960
   4: [99616..140575]:    10315872..10356831  0 (10315872..10356831) 40960
   5: [140576..181535]:   10274912..10315871  0 (10274912..10315871) 40960
   6: [181536..222495]:   10233952..10274911  0 (10233952..10274911) 40960
   7: [222496..263455]:   10192992..10233951  0 (10192992..10233951) 40960
   8: [263456..304415]:   10152032..10192991  0 (10152032..10192991) 40960
   9: [304416..345359]:   10111088..10152031  0 (10111088..10152031) 40944
  10: [345360..385919]:   10070520..10111079  0 (10070520..10111079) 40560
  11: [385920..425879]:   10030560..10070519  0 (10030560..10070519) 39960
  12: [425880..466199]:   9990240..10030559   0 (9990240..10030559)  40320
  13: [466200..506543]:   9949896..9990239    0 (9949896..9990239)   40344
  14: [506544..547343]:   9909096..9949895    0 (9909096..9949895)   40800
  15: [547344..588303]:   9868136..9909095    0 (9868136..9909095)   40960
  16: [588304..629223]:   9827216..9868135    0 (9827216..9868135)   40920
  17: [629224..670135]:   9786304..9827215    0 (9786304..9827215)   40912
  18: [670136..711055]:   9745384..9786303    0 (9745384..9786303)   40920
  19: [711056..752015]:   9704424..9745383    0 (9704424..9745383)   40960
  20: [752016..792895]:   9663544..9704423    0 (9663544..9704423)   40880
  21: [792896..833807]:   9622632..9663543    0 (9622632..9663543)   40912
  22: [833808..874767]:   9581672..9622631    0 (9581672..9622631)   40960
  23: [874768..915687]:   9540752..9581671    0 (9540752..9581671)   40920
  24: [915688..956607]:   9499832..9540751    0 (9499832..9540751)   40920
  25: [956608..997487]:   9458952..9499831    0 (9458952..9499831)   40880
  26: [997488..1038447]:  9417992..9458951    0 (9417992..9458951)   40960
  27: [1038448..1079343]: 9377096..9417991    0 (9377096..9417991)   40896
  28: [1079344..1120271]: 9336168..9377095    0 (9336168..9377095)   40928
  29: [1120272..1161231]: 9295208..9336167    0 (9295208..9336167)   40960
  30: [1161232..1202191]: 9254248..9295207    0 (9254248..9295207)   40960
  31: [1202192..1243151]: 9213288..9254247    0 (9213288..9254247)   40960
  32: [1243152..1284111]: 9172328..9213287    0 (9172328..9213287)   40960
  33: [1284112..1325071]: 9131368..9172327    0 (9131368..9172327)   40960
  34: [1325072..1374223]: 9082216..9131367    0 (9082216..9131367)   49152
  35: [1374224..1423375]: 9033064..9082215    0 (9033064..9082215)   49152
  36: [1423376..1472527]: 8983912..9033063    0 (8983912..9033063)   49152
  37: [1472528..1521679]: 8934760..8983911    0 (8934760..8983911)   49152
  38: [1521680..1570815]: 8885624..8934759    0 (8885624..8934759)   49136
  39: [1570816..1619967]: 8836472..8885623    0 (8836472..8885623)   49152
  40: [1619968..1669095]: 8787344..8836471    0 (8787344..8836471)   49128
  41: [1669096..1718247]: 8738192..8787343    0 (8738192..8787343)   49152
  42: [1718248..1767391]: 8689048..8738191    0 (8689048..8738191)   49144
  43: [1767392..1816543]: 8639896..8689047    0 (8639896..8689047)   49152
  44: [1816544..1865695]: 8590744..8639895    0 (8590744..8639895)   49152
  45: [1865696..1914847]: 8541592..8590743    0 (8541592..8590743)   49152
  46: [1914848..1963991]: 8492448..8541591    0 (8492448..8541591)   49144
  47: [1963992..2013143]: 8443296..8492447    0 (8443296..8492447)   49152
  48: [2013144..2062295]: 8394144..8443295    0 (8394144..8443295)   49152
  49: [2062296..2111447]: 8344992..8394143    0 (8344992..8394143)   49152
  50: [2111448..2160599]: 8295840..8344991    0 (8295840..8344991)   49152
  51: [2160600..2209743]: 8246696..8295839    0 (8246696..8295839)   49144
  52: [2209744..2251767]: 8204672..8246695    0 (8204672..8246695)   42024

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Liv2Cod
 Post subject:
PostPosted: Sun Jul 20, 2008 12:17 pm 
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Joined: Fri May 21, 2004 11:55 pm
Posts: 1206
Location: Silicon Valley, CA
Well, I dunno if yours is a problem, but here's my XFS partition that's been used for a year or so...

Code:
xfs_db> frag
actual 124184, ideal 140, fragmentation factor 99.89%

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graysky
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PostPosted: Sun Jul 20, 2008 12:42 pm 
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Joined: Wed Dec 10, 2003 8:31 pm
Posts: 1996
Location: /dev/null
Thanks for the reply. Have you tried to defrag that partition? Also, are you using the allocsize=512 meg switch in your /etc/fstab as suggested on this mythtv.org wiki page?

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Liv2Cod
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PostPosted: Sun Jul 20, 2008 5:46 pm 
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Location: Silicon Valley, CA
Naaa... I just set it up a loooong time ago and ran it. I haven't really noticed anything bad. I guess the suggested setup is good, but won't it make each entry in "pretty" take up 1/2 gig? Maybe not, since they're just links.

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graysky
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PostPosted: Sun Jul 20, 2008 6:17 pm 
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Location: /dev/null
Yeah, I dunno exactly how that works... I will say that mine captured several 12 hour shows and the fragment load hasn't changed really.. still under 1 %.

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graysky
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PostPosted: Sat Jul 26, 2008 5:09 am 
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Joined: Wed Dec 10, 2003 8:31 pm
Posts: 1996
Location: /dev/null
This fragmentation effect seems to be unique to both SAMBA and accessing files from the local DVDROM drive. If I load up files from ftp, they are not fragmented at all.

For example, I just downloaded about 5 video files (5 gigs totally) and if I inspect each one with xfs_bmap, each of the 5 are completely solid (i.e no fragments). Contrast that with moving a file via SAMBA or simply reading it off the local DVDROM, and I'm left with results like I posted above (first post of the thread).

Very odd!

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marc.aronson
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PostPosted: Sat Jul 26, 2008 7:57 am 
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Location: California
I've been using the "alloc size" setting for over a year now, but still had 98% fragmentation levels. I now have my machine defrag for 20 minutes once/day just before it shuts itself down and my fragmentation levels are at or near 0. I'm not sure that it has a material impact on my performance, but it feel good to keep your room clean :-).

Marc
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