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Fri, 30 May 2008

Local filesystem randomg read/write performance. POHMELFS parallel testing.

I promised to publish POHMELFS parallel processing results yesterday, even if they are miserable. Unfortunately there are no interesting results at all. In the released version POHMELFS is 32bit only, since it does not have special ->open() callback which forces to open files with O_LARGEFILE flag to support more than 4Gb (actually only 2Gb, since kernel uses signed size_t, which is only 31 bit large) sizes and superblock maximum size is set to 32 bits, so all 32 bit results are not very interesting, since having 2Gb/s random read speed is really stupid sentence, since all reading happend from the cache.

While results with more than 2Gb are... Let me first show you how XFS and Ext3 behave in case of random writes.

A short preface.
Hardware used in testing: 4-way Intel E7520 system (two logical and two physical CPUs) 3Ghz 32 bit Xeons with 8gb of ram, Adaptec AIC7902 Ultra320 SCSI adapter with SEAGATE ST3300007LC 10k rpm 300 Gb testing disk.
Its linear reading speed is about 90 MB/s. Dmesg:

scsi0 : Adaptec AIC79XX PCI-X SCSI HBA DRIVER, Rev 3.0
        <Adaptec AIC7902 Ultra320 SCSI adapter>
        aic7902: Ultra320 Wide Channel A, SCSI Id=7, PCI-X 67-100Mhz, 512 SCBs
scsi 0:0:2:0: Direct-Access     SEAGATE  ST3300007LC      0003 PQ: 0 ANSI: 3
 target0:0:2: asynchronous
scsi0:A:2:0: Tagged Queuing enabled.  Depth 32
 target0:0:2: Beginning Domain Validation
 target0:0:2: wide asynchronous
 target0:0:2: FAST-160 WIDE SCSI 320.0 MB/s DT IU QAS RDSTRM RTI WRFLOW PCOMP (6.25 ns, offset 63)
 target0:0:2: Ending Domain Validation
Kernel version is 2.6.25 (and 2.6.24 for the first ext3 test).

I used two such machines as servers for iozone read/reread, write/rewrite and random read/write testing. File size is limited to 8Gb only, since it is the only interesting fair case, record size varies from 8Kb to 1Mb.

Before I started 8Gb POHMELFS testing, I decided to check how local filesystem behave in such scenario.
XFS was tuned this way: (mkfs.xfs -d agcount=75 -l size=64m /dev/sdc1; mount -o logbufs=8,nobarrier,noatime,nodiratime,osyncisdsync /dev/sdc1 /mnt/)
Ext3 was created and mounted with default options on machine with only 4Gb of RAM though.

So, testing.
Here is a results table from iozone (before I interrupted it) with read/reread, write/rewrite and random read/write tests for XFS (either default, or tuned like on link above).
                                                   random  random
     KB  reclen   write rewrite    read    reread    read   write
8388608       8   73671   64052    77565    80107   35281    5085
8388608      16   74437   66095    77611    80065   66854    8808
8388608      32   74683   66780    77564    80202  121442   14576
8388608      64   74936   66908    77537    80372  215377   22583
8388608     128   74928   68598    77542    80247  339304   32280
8388608     256   73609   69615    77534    80143  365081   40571
8388608     512   73763   69830    77547    80317  420704   48501
8388608    1024   73940   69474    77602    80065  406266   47295
I.e. 5 MB/s random write speed for 8kb record!

Do you really want to know ext3 speed? Pregnant kids and women should skip next paragraph.
I interrupted test after almost 2 (!) hours or random writing of 8Gb file with 8Kb records on default ext3. Test was not completed and I do not really know its performance (note, that this machine has only 4Gb of ram, other hardware details were described above), but it will be less than 1 MB/s.
Ext4 behaves much better in this aspect (ount options: rw,noatime,data=writeback,extents):
                                                   random  random
     KB  reclen   write rewrite    read    reread    read   write
8388608       8   69593   74200    77324    81340   35538    5088
8388608      16   66745   70038    73676    77271   65715    8704
8388608      32   68253   70320    73652    77258  121690   14469
8388608      64   68421   71291    73653    77042  209629   22005
8388608     128   68438   71340    73658    76988  332021   30381
8388608     256   68921   71254    73651    76912  435586   40683
8388608     512   69079   71728    73551    76815  549136   49298
8388608    1024   66611   71217    73683    76581  552459   49220
POHMELFS results are coming...

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