[nflug] RE: Partitions sizes

[Cyber Source]

Dave Andruczyk wrote:

>--- Ron Maggio <ronmaggio2005 at yahoo.com> wrote:
>
>  
>
>>Hi, Dave
>>  Thanks for all your advice.
>>   
>>  So your going to add HDD's later on down the road, and from what your
>>saying is that LVM will let you add them on and divide them up on the fly. So
>>by doing so you can add partitions, and from what I've read about using LVM
>>one can move (resizing partitions) them around without destroying data. So if
>>I'm correct one can do partition extensions, similar to NT's volume striping
>>to increase partition space? Linux has come a long way!
>>   
>>    
>>
>
>Yes, what I'm planning on is picking up at least one Samsung Spinpoint P series
>250GB drive (about $100.00 from newegg.com) and a SCSI to IDE bridge to allow
>me to run it on my U160 SCSI bus (I don't care for IDE interfaces as if you run
>more than one drive per channel performance goes to hell)  Since I still have
>about 12 ID's free on the SCSI bus I could add a couple more before being BW
>limited on the SCSI bus,  as this drive can't push more than about
>35-40MB/second. theoretically I could have 4 of these on the SCSI bus running
>in a RAID5 configuration and just nearly saturate that SCSI channel. (though I
>have a second channel available)  whereas I'd need four independant IDE
>channels to do the same thing, and I wouldn't have the advantages of command
>queuing that SCSI gives me (the SCSI/IDE bridge does TCQ, Tagged command
>Queuing)
>
>Once this drive is in, it'll have a static /boot partition and the rest will be
>LVM'd and split up as needed. if I add another drive, I can just LVM extend the
>volume group to encompase both drives and now more space is available to extent
>ANY partition on the LVM group.  the LVM core takes care of whereto put the
>data.   Beware though that if hte drives are not in a redundant configuration.
>(i.e. hardware raid 1/5) that adding drives together in a linear fashion will
>increase the likelihood of dataloss as it'll only take one out of the group of
>drives to fail to cause potential data loss..
>
>
>Dave J. Andruczyk
>
>
>		
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>  
>
Dave,
  If you've never worked with LVM as far as extending, I might be able 
to save you some hair pulling. I worked with LVM2 and wanted to combine 
a 200GB and 80GB drive here on our network to be used as a backup server 
for our shop. After much hair pulling I found that LVM2 has some bugs, 
one of which seems to be when your trying to extend large partitions. 
The docs said something about limitations, I think I remember something 
like 60GB but that was a while ago, anywho, I ended up making all 20GB 
partitions and then just extending to them all, not a very clean method 
but it worked for me and what I was doing. This is on and old box with 
ATA33 IDE. I know your a Gentoo guy, the LVM on that might not have 
those bugs or maybe they have been fixed in newer releases but if there 
not, this could save you from thinking your doing something wrong when 
your not.
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