On Sunday 29 August 2010 03:24:42 Nikos Chantziaras wrote:
> On 08/28/2010 10:42 PM, Dale wrote:
> > Alex Schuster wrote:
> >> Dale writes:
> >>> It would be nice if something like *fdisk could edit the labels tho.
> >>> It would be so much easier. I didn't see anything in the man pages
> >>> tho.
> >>
> >> I'd like this, too. cfdisk displays them, but is not abel to edit.
> >>
> >>> I looked into LVM a good while ago. It's just to much for me to keep
> >>> up with since I just have a desktop system here. It has its good
> >>> points but just way overkill for what I have here.
> >>
> >> It's not that complicated. In a nutshell:
> >>
> >> Choose the partitions you want to use for LVM, and prepare them to be
> >> physical volumes:
> >> pvcreate /dev/sda[678]
> >>
> >> Create a volume group out of these partitions:
> >> vgcreate myvg /dev/sda[678]
> >>
> >> Create logical volumes in this volume group:
> >> lvcreate -L 5G -n lvm1 myvg
> >> lvcreate -L 2G -n lvm2 myvg
> >>
> >> Use these logical volumes just as disk partitions:
> >>
> >> mke2fs -j -L fs_on_lvm /dev/myvg/lvm1
> >> mount /dev/myg/lvm1 /mnt/fs_on_lvm
> >>
> >> The file system is too small? Just extend its size by 1G, without
> >> unmouning:
> >>
> >> lvresize -L +1G /dev/myvg/lvm1
> >>
> >> The volume groups is getting full, no space to add LVMs? Add other
> >> partitions. If you like, even from a 2nd drive:
> >>
> >> pvcreate /dev/sdb5
> >> vgextend myvg /dev/sdb5
> >>
> >> So, it's of course more complicated than just firing up cfdisk, create
> >> partitions and file systems on them, but you have much more flexibility.
> >> Once you have LVM, you do not have to care what the actual device
> >> names of
> >> your drives are. If sda becomes sdb and vice versa, no problem, and
> >> nothing to worry about. LVM does not use the device name, it scans each
> >> partition and uses the LVM UUIDs on them to identify what is what.
> >>
> >> Wonko
> >
> > Since I finally got this thing settled with partition sizes, that's
> > pretty complicated. I have root, /boot, /home, portage and a data
> > partition for misc. junk. I doubt it will change any in the near future.
> >
> > I did read up on it one time a while back. It's neat when you have to
> > add drives and resize things but still a bit much for a little desktop.
>
> I'd stay away from LVM. I started using it on a Debian Lenny machine
> and performance went down the drain. For example, deleting a 3GB file
> was almost instant and now it takes like 15 seconds. It's almost as if
> with LVM, deleting a file means writing 0 all over the 3GB first :-/
That sounds like a different issue.
I haven't noticed any major performance issues myself.
But to test quickly:
LVM:
# ~/speedtest $ time dd if=/dev/zero of=3gigfile bs=1024 count=3000000
3000000+0 records in
3000000+0 records out
3072000000 bytes (3.1 GB) copied, 33.3029 s, 92.2 MB/s
real 0m33.305s
user 0m0.440s
sys 0m16.370s
# ~/speedtest $ time rm 3gigfile
real 0m3.827s
user 0m0.000s
sys 0m1.131s
# hdparm -Tt /dev/sda
/dev/sda:
Timing cached reads: 4758 MB in 2.00 seconds = 2379.87 MB/sec
Timing buffered disk reads: 274 MB in 3.02 seconds = 90.84 MB/sec
**************
Non-LVM:
# /data/speedtest $ time dd if=/dev/zero of=3gigfile bs=1024 count=3000000
3000000+0 records in
3000000+0 records out
3072000000 bytes (3.1 GB) copied, 38.2821 s, 80.2 MB/s
real 0m38.284s
user 0m0.397s
sys 0m9.490s
# /data/speedtest $ time rm 3gigfile
real 0m0.721s
user 0m0.000s
sys 0m0.720s
# hdparm -Tt /dev/sdb
/dev/sdb:
Timing cached reads: 3396 MB in 2.00 seconds = 1698.30 MB/sec
Timing buffered disk reads: 252 MB in 3.00 seconds = 83.94 MB/sec
Both filesystems are ext3
Based on this, it takes about 3 seconds more. That is something I can easily
live with.
But instantaneous to 15 seconds, I think there might be some other factors
there?
--
Joost
