Setting up Venti
D1211654894
Ajeg
#You'll want to run Venti from raw disk partitions rather than files
#on a file system.
#
#If you want to mirror your partitions using several disks, read the
#last section of [setting up fossil] to see an example of how to use
#fs(3) to do that.
#
#Venti storage is divided into a log holding the data and an index
#mapping SHA1 hash to position in the log. The log is split into
#fixed-size (say, 500MB) chunks called arenas. There may be more than
#one file holding arenas for the Venti server. Their concatenation
#forms the actual log. The index is made up of individual index
#section files. You want about 5% as much index space as you have
#arena space. So if you have 100GB of arenas, plan on 5GB of index.
#
#Use disk/fdisk to create a Plan 9 partition on the disks you wish to
#use for Venti. Then use disk/prep to subdivide the Plan 9 partition
#into the arena files or index sections that Venti will use. The rest
#of this document assumes that you named the arena files
#/dev/sdC0/arenas{0,1} and that you named the index sections
#/dev/sdC0/isect{0,1}.
#
#Format the arenas with:
#
#! venti/fmtarenas arenas0 /dev/sdC0/arenas0
#! venti/fmtarenas arenas1 /dev/sdC0/arenas1
#
#Format the index sections with:
#
#! venti/fmtisect isect0 /dev/sdC0/isect0
#! venti/fmtisect isect1 /dev/sdC0/isect1
#
#Note that formatting the arenas and the index sections zeros the
#disk partitions, so it takes a long time.
#
#Create a venti.conf file containing:
#
#! # the name of the index
#! index main
#! 
#! # the index sections
#! isect /dev/sdC0/isect0
#! isect /dev/sdC0/isect1
#! 
#! # the arenas
#! arenas /dev/sdC0/arenas0
#! arenas /dev/sdC0/arenas1
#
#Format the index itself with:
#
#! venti/fmtindex venti.conf
#
#Note that once you format the index you should not change the order
#of the index sections nor should you change the order of the arenas.
#It is safe to add new arenas.
#
#If you plan on booting the machine with venti/fossil as your root
#you should write the venti config into the arenas0 file:
#
#! venti/conf -w /dev/sdC0/arenas0 < venti.conf
#
#Now the disks are ready. You can start the Venti server with
#
#! venti/venti -w
#
#The file venti.conf must be in the current directory.
#
#Set the environment variable: venti=your-ip-address
#
#if required, you can put this in the startup scripts like
#/rc/bin/termrc. You can also add this line in plan9.ini
#
#Test the server with:
#
#! vac -f /tmp/x.vac /adm
#! vacfs /tmp/x.vac
#! ls -l /n/vac
#
#Congratulations! You have a Venti.
#
#If you plan on booting with venti/fossil as your root you should add
#venti=/dev/sdC0/arenas0 in your plan9.ini. During boot the
#configuration file previously written to the start of this partition
#with the venti/conf program will be read back and used.
#
#See venti.conf(6), venti(8), and ventiaux(8) for more information.
#
#PERFORMANCE
#
#If you're worried about performance, start the subpartitions at
#sector offsets that are multiples of 16 so that 8k reads will be
#8k-aligned on the disk. Or use type other in disk/fdisk for the
#partitions, but then you don't get such good partition names.
#
#Venti's performance is tied to the number of index sections. If
#you're going for high performance, get a handful of small disks to
#use for the index, so that many reads can happen in parallel.
#
#SECURITY
#
#By default Venti accepts connections from anyone, anywhere.
#
#If you are running in a hostile environment and don't want just
#anyone connecting to your Venti server, you can run it on the
#loopback device. Add loopbackmedium to your kernel (it's already in
#the pccpu and pcauth kernels) and then run
#
#! ip/ipconfig loopback /dev/null 127.1
#
#to set up a loopback IP address. (Note that the loopback medium is
#not compiled into the PC kernel by default). Then you can start
#Venti with
#
#! venti/venti -a tcp!127.1!venti -h tcp!127.1!http -w
#
#and it will only take connections from 127.1.
#
#TEMPORARY FILES AND DIRECTORIES
#
#For some purposes it is desirable to exclude files or directories
#from being archived to venti. For example, if you want your
#$home/tmp excluded, set the 't' flag (temporary) for it (see
#chmod(1) for details):
#
#! chmod +t $home/tmp
#
#After that, no files in tmp will be archived to venti. You can set
#the 't' flag for files, too
#
#LIVING WITH VENTI: VAC SCORES AND FLFMT
#
#The vac score given on the fossil console after an archival snapshot
#differs from the scores given by the vac command (on the console).
#Only the former contains /active, /snapshot and /archive. And only
#the former can therefore be used to do a flfmt -v <score>
#
#The vac command won't show up these root scores. But Russ Cox posted
#scripts to the 9fans mailinglist. One of them gets the most recent
#root score of a particular fossil and the other one prints the
#scores subsequent to it.
#
#You can find the scripts (and his explanation) on
#[http://lists.cse.psu.edu/archives/9fans/2003-March/023470.html]
#