Alexander Leidinger

Just another weblog

Apr
27

ADSL RAM … finally aban­doned (but with good news)

As I already wrote, the­o­ret­i­cally ADSL RAM is avail­able at my place. The analy­sis of the sit­u­a­tion revealed first that the ISP side of my line uses out­dated hard­ware. After the tech­ni­cian I know unof­fi­cially took care about it (remotely switch­ing me to a dif­fer­ent port), I have seen an imme­di­ate improve­ment of the sig­nal to noise ratio. It is about 20 dB better.

Unfor­tu­nately this was not enough to be able to switch to the rate adap­tive mode. Accord­ing to their data­base the line length allows to give me 1.5 MBit. My line is run­ning already at 2 MBit and my ADSL modem tells me it could do 8 MBit, so I dis­agree a bit with their database.

As the tech­ni­cian agrees with me, the next step would be to tem­po­rary move my house by some hun­dred meters towards the ISP end­point of the line, unfor­tu­nately the higher man­age­ment seems to be hav­ing some busi­ness ideas with our region (FTTT, Fiber To The Town (which means we will prob­a­bly get 16 MBit via ADSL) … but maybe even FTTH), so they are now mon­i­tor­ing the data­base for such changes since a while.

I have the impres­sion they seem to pre­vent such changes to the data­base because they think that if peo­ple get 2 MBit (instead of noth­ing, large parts of a town nearby does not even have the slow­est ADSL con­nec­tion) or 8 MBit (instead of 2 MBit), they are not inter­ested in get­ting FTTH (or 16 MBit). Together with their IPTV ini­tia­tive I do not really under­stand it. To get their IPTV, you need to have at least a 8 MBit line. With 8 MBit you can only cover one TV at SD res­o­lu­tion (at least with their IPTV offer), if you want HD res­o­lu­tion, you need to switch to their VDSL stuff (which is not avail­able in our town). What peo­ple are doing cur­rently is to switch to a cable provider where they can get about 32 MBit (I do not switch, switch­ing is a risky action here, I rather stay with a slow con­nec­tion that to have no con­nec­tion at all for some months). With 32 MBit (and TV) peo­ple have less a need to switch to fiber (and pay 150 EUR for the work to get fiber into the house) than with 2 MBit or nothing.

The final out­come is, that the tech­ni­cian I know does not want to ask some­one to play with the data­base to move my house tem­po­rary (which I can under­stand). The good part of those news is, that I may get more than 8 MBit in the not so dis­tant future (the cur­rent plan­ning is to fin­ish the FTTT work until autumn).

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Apr
19

Solaris UFS full while df shows plenty of free space/inodes

At work we have a Solaris 8 with a UFS which told the appli­ca­tion that it can not cre­ate new files. The df com­mand showed plenty if free inodes, and there was also enough space free in the FS. The rea­son that the appli­ca­tion got the error was that while there where still plenty of frag­ments free, no free block was avail­able any­more. You can not cre­ate a new file only with frag­ments, you need to have at least one free block for each new file.

To see the num­ber of free blocks of a UFS you can call “fstyp –v | head –18″ and look at the value behind “nbfree”.

To get this work­ing again we cleaned up the FSlit­tle bit (compressing/deleting log files), but this is only a tem­po­rary solu­tion. Unluck­ily we can not move this appli­ca­tion to a Solaris 10 with ZFS, so I was play­ing around a lit­tle bit to see what we can do.

First I made a his­togram of the file sizes. The backup of the FS I was play­ing with had a lit­tle bit more than 4 mil­lion files in this FS. 28.5% of them where smaller than or equal 512 bytes, 31.7% where smaller than or equal 1k (frag­ment size), 36% smaller than or equal 8k (block size) and 74% smaller than or equal 16k. The fol­low­ing graph shows in red the crit­i­cal part, files which need a block and pro­duce frag­ments, but can not life with only fragments.

chart

Then I played around with newfs options for this one spe­cific FS with this spe­cific data mix. Chang­ing the num­ber of inodes did not change much the out­come for our prob­lem (as expected). Chang­ing the opti­miza­tion from “time” to “space” (and restor­ing all the data from backup into the empty FS) gave us 1000 more free blocks. On a FS which had 10 Mio free blocks when empty this is not much, but we expect that the restore con­sumes less frag­ments and more full blocks than the live-FS of the appli­ca­tion (we can not com­pare, as the con­tent of the live-FS changed a lot since we had the prob­lem). We assume that e.g. the logs of the appli­ca­tion are split over a lot of frag­ments instead of full blocks, due to small writes to the logs by the appli­ca­tion. The restore should write all the data in big chunks, so our expec­ta­tion is that the FS will use more full blocks and less frag­ments. Because of this we expect that the live-FS with this spe­cific data mix could ben­e­fit from chang­ing the optimization.

I also played around with the frag­ment size. The expec­ta­tion was that it will only change what is reported in the out­put of df (reduc­ing the reported avail­able space for the same amount of data). Here is the result:

chart

The dif­fer­ence between 1k (default) and 2k is not much. For 8k we would have to much unused space lost. The frag­ment size of 4k looks like it is accept­able to get a bet­ter mon­i­tor­ing sta­tus of this par­tic­u­lar data mix.

Based upon this we will prob­a­bly cre­ate a new FS with a frag­ment size of 4k and we will prob­a­bly switch the opti­miza­tion directly to “space”. This way we will have a bet­ter report­ing on the fill level of the FS for our data mix (but we will not be able to fully use the real space of the FS) and as such our mon­i­tor­ing should alert us in time to do a cleanup of the FS or to increase the size of the FS.

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Apr
19

DTrace probes for the Lin­ux­u­la­tor updated

If some­one had a look at the ear­lier post about DTrace probes for the Lin­ux­u­la­tor: I updated the patch at the same place. The dif­fer­ence between the pre­vi­ous one is that some D–scripts are fixed now to do what I meant, spe­cially the ones which pro­vide sta­tis­tics output.

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Apr
01

Com­pil­ing Samba 3.5.8 with AD sup­port on Solaris 10 u8

If some­one needs a samba which is able to com­mu­ni­cate with an AD 2008 server on a Solaris 10 sys­tem… here is how I did it.

Pre­req­ui­sites

  • /opt/SUNWspro con­tains the Stu­dio 12 compiler
  • tar­balls of openl­dap–sta­ble–20100719 (2.4.23), heimdal-1.4, samba-3.5.8
  • export PATH=/opt/SUNWspro/bin:/usr/xpg6/bin:/usr/xpg4/bin:/usr/perl5/bin:/usr/bin:/usr/openwin/bin:/bin:/usr/sfw/bin:/usr/sfw/sbin:/sbin:/usr/sbin:/usr/sadm/admin/bin:/usr/sadm/bin:/usr/java/jre/bin:/usr/ccs/bin:/usr/ucb CC=cc CXX=CC
  • DEST=/path/to/final/location

Com­pil­ing everything

openldap-stable-20100719 (2.4.23)

export CPPFLAGS=”-I/usr/sfw/include” LDFLAGS=”-L/usr/sfw/lib –R/usr/sfw/lib“
./configure –pre­fix=$DEST/openldap-2.4.23 –disable-slapd
make depend
make install

heimdal-1.4

./configure –prefix=$DEST/heimdal-1.4 –with-openldap=$DEST/openldap-2.4.23 –with-hdbdir=$DEST/heimdal-instance/var/heimdal –sysconfdir=$DEST/heimdal-instance/etc
cd lib/hcrypto/libtommath

Unfor­tu­nately heimdal-1.4 does not con­tain all the files you need. As of this writ­ing (if you try to do this a lot later, you may get more recent ver­sions which may or may not work with heim­dal 1.4) I was able to down­load them from

cd ../../..
make
make install
mkdir –p $DEST/heimdal-instance/var/heimdal $DEST/heimdal-instance/etc

samba-3.5.8

export CPPFLAGS=”-I$DEST/openldap-2.4.23/include” LDFLAGS=”-L$DEST/openldap-2.4.23/lib –R$DEST/openldap-2.4.23/lib –R$DEST/samba-3.5.8/lib –R$DEST/heimdal-1.4/lib“
./configure –prefix=$DEST/samba-3.5.8 –sysconfdir=$DEST/samba-instance/etc –localstatedir=$DEST/samba-instance/var –with-privatedir=$DEST/samba-instance/private –with-lockdir=$DEST/samba-instance/var/locks –with-statedir=$DEST/samba-instance/var/locks –with-cachedir=$DEST/samba-instance/var/locks –with-piddir=$DEST/samba-instance/var/locks –with-ncalrpcdir=$DEST/samba-instance/var/ncalrpc –with-configdir=$DEST/samba-instance/con­fig –with-ldap –with-krb5=$DEST/heimdal-1.4 –with-ads –with-quotas –with-aio-support –with-shared-modules=vfs_zfsacl
gmake
gmake install

After that you have a samba in $DEST/samba-3.5.8, the con­fig for it should be put into $DEST/samba-instance/config and if you need to have a cus­tom krb4.conf you can put it int $DEST/heimdal-instance/etc/.

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