Re: Understanding VDO vs ZFS

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Strahil,
I am using about 1012MB for the first ISO. I believe it's because of
compression. From there vdostats --hu reports 5.0G usage and 12% in
percentage. With savings of 89% for original + 9 copies of the same ISO.


On Sun, May 3, 2020 at 1:17 AM Strahil Nikolov <hunter86_bg@xxxxxxxxx>
wrote:

> On May 3, 2020 8:33:33 AM GMT+03:00, Erick Perez - Quadrian Enterprises <
> eperez@xxxxxxxxxxxxxxx> wrote:
> >sorry corrections:
> >For this test I created a 40GB lvm volume group with /dev/sdb and
> >/dev/sdc
> >then a 40GB LV
> >then a 60GB VDO vol (for testing purposes)
> >
> >vdostats --verbose /dev/mapper/vdoas | grep -B6 'saving percent'
> >output from just created vdoas
> >
> >[root@localhost ~]# vdostats --verbose /dev/mapper/vdoas | grep -B6
> >'saving
> >percent'
> >physical blocks                     : 10483712
> >  logical blocks                      : 15728640
> >  1K-blocks                           : 41934848
> >  1K-blocks used                      : 4212024
> >  1K-blocks available                 : 37722824
> >  used percent                        : 10
> >  saving percent                      : 99
> >[root@localhost ~]#
> >
> >FIRST copy CentOS-7-x86_64-Minimal-2003.iso (1.1G) to vdoas from source
> >outside vdo volume
> >[root@localhost ~]# vdostats --verbose /dev/mapper/vdoas | grep -B6
> >'saving
> >percent'
> >  1K-blocks used                      : 4721348
> >  1K-blocks available                 : 37213500
> >  used percent                        : 11
> >  saving percent                      : 9
> >
> >SECOND copy  CentOS-7-x86_64-Minimal-2003.iso (1.1G) to vdoas form
> >source
> >outside vdo volume
> >#cp /root/CentOS-7-x86_64-Minimal-2003.iso
> >/mnt/vdomounts/CentOS-7-x86_64-Minimal-2003-version2.iso
> >  1K-blocks used                      : 5239012
> >  1K-blocks available                 : 36695836
> >  used percent                        : 12
> >  saving percent                      : 52
> >
> >THIRD  copy  CentOS-7-x86_64-Minimal-2003.iso (1.1G) to
> >vdoas form inside vdo volume to inside vdo volume
> >  1K-blocks used                      : 5248060
> >  1K-blocks available                 : 36686788
> >  used percent                        : 12
> >  saving percent                      : 67
> >
> >Then I did this a total of 9 more times to have 10 ISOs copied. Total
> >data
> >copied 10.6GB.
> >
> >
> >Do note this:
> >When using DF, it will show the VDO size, in my case 60G
> >when using vdostats it will show the size of the LV, in my case 40G
> >Remeber dedupe AND compression are enabled.
> >
> >The df -hT output shows the logical space occupied by these iso files
> >as
> >seen by the filesystem on the VDO volume.
> >Since VDO manages a logical to physical block map, df sees logical
> >space
> >consumed according to the file system that resides on top of the VDO
> >volume.
> >vdostats --hu is viewing the physical block device as managed by VDO.
> >Physically a single .ISO image is residing on the disk, but logically
> >the
> >file system thinks there are 10 copies, occupying 10.6GB.
> >
> >So at the end I have 10 .ISOs of 1086 1MB blocks (total 10860 1MB
> >blocks)
> >that yield these results:
> >  1K-blocks used                      : 5248212
> >  1K-blocks available                 : 36686636
> >  used percent                        : 12
> >  saving percent                      : 89
> >
> >So at the end it is using 5248212 1K blocks minus  4212024  initial
> >used 1K
> >blocks, gives (5248212 - 4212024) = 1036188 1K blocks / 1024 = about
> >1012MB
> >total.
> >
> >Hope this helps understanding where the space goes.
> >
> >BTW: Testing system is CentOS Linux release 7.8.2003 stock. with only
> >"yum
> >install vdo kmod-kvdo"
> >
> >History of commands:
> >[root@localhost vdomounts]# history
> >    2  pvcreate /dev/sdb
> >    3  pvcreate /dev/sdc
> >    8  vgcreate -v -A y vgvol01 /dev/sdb /dev/sdc
> >    9  vgdisplay
> >   13  lvcreate -l 100%FREE -n lvvdo01 vgvol01
> >   14   yum install vdo kmod-kvdo
> >   18  vdo create --name=vdoas --device=/dev/vgvol01/lvvdo01
> >--vdoLogicalSize=60G --writePolicy=async
> >   19  mkfs.xfs -K /dev/mapper/vdoas
> >   20  ls /mnt
> >   21  mkdir /mnt/vdomounts
> >   22  mount /dev/mapper/vdoas /mnt//vdomounts/
> >   26  vdostats --verbose /dev/mapper/vdoas | grep -B6 'saving percent'
> >   28  cp /root/CentOS-7-x86_64-Minimal-2003.iso /mnt/vdomounts/ -vvv
> >   29  vdostats --verbose /dev/mapper/vdoas | grep -B6 'saving percent'
> >   30  cp /root/CentOS-7-x86_64-Minimal-2003.iso
> >/mnt/vdomounts/CentOS-7-x86_64-Minimal-2003-version2.iso
> >   31  vdostats --verbose /dev/mapper/vdoas | grep -B6 'saving percent'
> >   33  cd /mnt/vdomounts/
> >   35  cp CentOS-7-x86_64-Minimal-2003-version2.iso
> >./CentOS-7-x86_64-Minimal-2003-version3.iso
> >   36  vdostats --verbose /dev/mapper/vdoas | grep -B6 'saving percent'
> >   37  df
> >   39  vdostats --hu
> >   40  ls -l --block-size=1MB /root/CentOS-7-x86_64-Minimal-2003.iso
> >   41  df -hT
> >   42  vdo status | grep Dedupl
> >   43  vdostats --hu
> >   44  vdostats
> >   48  cp CentOS-7-x86_64-Minimal-2003-version2.iso
> >./CentOS-7-x86_64-Minimal-2003-version4.iso
> >   49  cp CentOS-7-x86_64-Minimal-2003-version2.iso
> >./CentOS-7-x86_64-Minimal-2003-version5.iso
> >   50  cp CentOS-7-x86_64-Minimal-2003-version2.iso
> >./CentOS-7-x86_64-Minimal-2003-version6.iso
> >   51  cp CentOS-7-x86_64-Minimal-2003-version2.iso
> >./CentOS-7-x86_64-Minimal-2003-version7.iso
> >   52  cp CentOS-7-x86_64-Minimal-2003-version2.iso
> >./CentOS-7-x86_64-Minimal-2003-version8.iso
> >   53  cp CentOS-7-x86_64-Minimal-2003-version2.iso
> >./CentOS-7-x86_64-Minimal-2003-version9.iso
> >   54  df -hT
> >   55  ls -l --block-size=1MB
> >   56  vdostats --hu
> >   57  df -hT
> >   58  df
> >   59  vdostats --hu
> >   60  vdostats
> >   61  vdostats --verbose /dev/mapper/vdoas | grep -B6 'saving percent'
> >   62  cat /etc/centos-release
> >   63  history
> >[root@localhost vdomounts]#
> >
> >
> >
> >
> >
> >On Sat, May 2, 2020 at 10:07 PM Erick Perez - Quadrian Enterprises <
> >eperez@xxxxxxxxxxxxxxx> wrote:
> >
> >> My two cents:
> >> 1- Do you have an encrypted filesystem on top of VDO? If yes, you
> >will see
> >> no benefit from dedupe.
> >> 2- can you post the stats of  vdostats –verbose /dev/mapper/xxxxx
> >(replace
> >> with your device)
> >>
> >> you can do something like:  "vdostats -verbose /dev/mapper/xxxxxxxx |
> >grep
> >> -B6 'save percentage'
> >>
> >>
> >>
> >>
> >> On Sat, May 2, 2020 at 9:54 PM david <david@xxxxxxxx> wrote:
> >>
> >>> Folks
> >>>
> >>> I'm looking for a solution for backups because ZFS has failed on me
> >>> too many times.  In my environment, I have a large amount of data
> >>> (around 2tb) that I periodically back up.  I keep the last 5
> >>> "snapshots".  I use rsync so that when I overwrite the oldest
> >backup,
> >>> most of the data is already there and the backup completes quickly,
> >>> because only a small number of files have actually changed.
> >>>
> >>> Because of this low change rate, I have used ZFS with its
> >>> deduplication feature to store the data.  I started using a Centos-6
> >>> installation, and upgraded years ago to Centos7.  Centos 8 is on my
> >>> agenda.  However, I've had several data-loss events with ZFS where
> >>> because of a combination of errors and/or mistakes, the entire store
> >>> was lost.  I've also noticed that ZFS is maintained separately from
> >>> Centos.  At this moment, the Centos 8 update causes ZFS to
> >>> fail.  Looking for an alternate, I'm trying VDO.
> >>>
> >>> In the VDO installation, I created a logical volume containing two
> >>> hard-drives, and defined VDO on top of that logical volume.  It
> >>> appears to be running, yet I find the deduplication numbers don't
> >>> pass the smell test.  I would expect that if the logical volume
> >>> contains three copies of essentially identical data, I should see
> >>> deduplication numbers close to 3.00, but instead I'm seeing numbers
> >>> like 1.15.  I compute the compression number as follows:
> >>>   Use df and extract the value for "1k blocks used" from the third
> >column
> >>>   use vdostats --verbose and extract the number titled "1K-blocks
> >used"
> >>>
> >>> Divide the first by the second.
> >>>
> >>> Can you provide any advice on my use of ZFS or VDO without telling
> >me
> >>> that I should be doing backups differently?
> >>>
> >>> Thanks
> >>>
> >>> David
> >>>
> >>> _______________________________________________
> >>> CentOS mailing list
> >>> CentOS@xxxxxxxxxx
> >>> https://lists.centos.org/mailman/listinfo/centos
> >>>
> >>
> >>
> >> --
> >>
> >> ---------------------
> >> Erick Perez
> >>
> >>
> >
> >--
> >
> >---------------------
> >Erick Perez
> >Quadrian Enterprises S.A. - Panama, Republica de Panama
> >Skype chat: eaperezh
> >WhatsApp IM: +507-6675-5083
> >---------------------
> >_______________________________________________
> >CentOS mailing list
> >CentOS@xxxxxxxxxx
> >https://lists.centos.org/mailman/listinfo/centos
>
> Hi Erick,
>
> In the end how much space is used as per vdostats ?
> Keep in mind that VDO keeps one slab for itself (default is 2GB) and also
> some metadata is written :
> https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/7/html/storage_administration_guide/vdo-qs-requirements#vdo-ig-storage-reqts
>
> Best Regards,
> Strahil Nikolov
>


-- 

---------------------
Erick Perez
Quadrian Enterprises S.A. - Panama, Republica de Panama
Skype chat: eaperezh
WhatsApp IM: +507-6675-5083
---------------------
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