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Fri, 14 Oct 2022 13:28:33 -0700 (PDT) Received: from [10.7.185.154] ([37.160.52.186]) by smtp.gmail.com with ESMTPSA id g7-20020a170906538700b00782539a02absm2038044ejo.194.2022.10.14.13.28.31 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 14 Oct 2022 13:28:32 -0700 (PDT) In-Reply-To: References: X-Referenced-Uid: 71205 Thread-Topic: Re: [linux-lvm] LVM2 : performance drop even after deleting the snapshot User-Agent: Android X-Is-Generated-Message-Id: true MIME-Version: 1.0 X-Local-Message-Id: <2e6bad30-2ebf-4162-b62d-092c3ad14003@gmail.com> From: Roberto Fastec Date: Fri, 14 Oct 2022 22:28:28 +0200 To: LVM general discussion and development Message-ID: <2e6bad30-2ebf-4162-b62d-092c3ad14003@gmail.com> X-Mimecast-Impersonation-Protect: Policy=CLT - Impersonation Protection Definition; Similar Internal Domain=false; Similar Monitored External Domain=false; Custom External Domain=false; Mimecast External Domain=false; Newly Observed Domain=false; Internal User Name=false; Custom Display Name List=false; Reply-to Address Mismatch=false; Targeted Threat Dictionary=false; Mimecast Threat Dictionary=false; Custom Threat Dictionary=false X-Scanned-By: MIMEDefang 3.1 on 10.11.54.1 X-Mailman-Approved-At: Mon, 17 Oct 2022 07:31:03 +0000 Subject: Re: [linux-lvm] LVM2 : performance drop even after deleting the snapshot X-BeenThere: linux-lvm@redhat.com X-Mailman-Version: 2.1.29 Precedence: list List-Id: LVM general discussion and development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: LVM general discussion and development Cc: Kapil Upadhayay , "lvm-devel@redhat.com" , Mitta Sai Chaithanya Errors-To: linux-lvm-bounces@redhat.com Sender: "linux-lvm" X-Scanned-By: MIMEDefang 3.1 on 10.11.54.7 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: multipart/mixed; boundary="===============3968364722874422570==" --===============3968364722874422570== Content-Type: multipart/alternative; boundary="----CF91JKVZ1DVZCB4Q5FIPZ79SHU8Q40" ------CF91JKVZ1DVZCB4Q5FIPZ79SHU8Q40 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=UTF-8 TIP and HINT forget SSDs with LVM unless of enterprise level=20 especially if you are going to use/implement the thin provisioning How to identify an SSD of enterprise level:=20 it costs from 1,00 euro per gigabyte up to 1,50 euro per gigabyte Kind regards Roberto Gini Technical Manager @ www.RecuperoDatiRAIDFAsTec.it=20 =E2=81=A3Ottieni BlueMail per Android =E2=80=8B Il giorno 14 ott 2022, 21:50, alle ore 21:50, Roger Heflin ha scritto: >What is the underlying disk hardware you are running this on? >virtual, spinning, ssd, nvme? > >On Thu, Oct 13, 2022 at 2:01 AM Pawan Sharma > wrote: >> >> adding this to lvm-devel mailing list also. >> >> Regards, >> Pawan >> ________________________________ >> From: Pawan Sharma >> Sent: Wednesday, October 12, 2022 10:42 PM >> To: linux-lvm@redhat.com >> Cc: Mitta Sai Chaithanya ; Kapil Upadhayay > >> Subject: LVM2 : performance drop even after deleting the snapshot >> >> Hi Everyone, >> >> >> We are evaluating lvm2 snapshots and doing performance testing on it. >This is what we are doing : >> >> dump some data to lvm2 volume (using fio) >> take the snapshot >> delete the snapshot (no IOs anywhere after creating the snapshot) >> run the fio on lvm2 volume >> >> Here as you can see, we are just creating the snapshot and >immediately deleting it. There are no IOs to the main volume or >anywhere. When we run the fio after this (step 4) and we see around 50% >drop in performance with reference to the number we get in step 1. >> >> It is expected to see a performance drop if there is a snapshot >because of the COW. But here we deleted the snapshot, and it is not >referring to any data also. We should not see any performance drop >here. >> >> Could someone please help me understand this behavior. Why are we >seeing the performance drop in this case? It seems like we deleted the >snapshot but still it is not deleted, and we are paying the COW >penalty. >> >> System Info: >> >> OS : ubuntu 18.04 >> Kernel : 5.4.0 >> >> # lvm version >> LVM version: 2.02.176(2) (2017-11-03) >> Library version: 1.02.145 (2017-11-03) >> Driver version: 4.41.0 >> >> We also tried on latest ubuntu with newer version of LVM. We got the >same behavior. >> >> Any help/pointers would be appreciated. Thanks in advance. >> >> Regards, >> Pawan >> _______________________________________________ >> linux-lvm mailing list >> linux-lvm@redhat.com >> https://listman.redhat.com/mailman/listinfo/linux-lvm >> read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/ > >_______________________________________________ >linux-lvm mailing list >linux-lvm@redhat.com >https://listman.redhat.com/mailman/listinfo/linux-lvm >read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/ ------CF91JKVZ1DVZCB4Q5FIPZ79SHU8Q40 Content-Type: text/html; charset=utf-8 Content-Transfer-Encoding: quoted-printable
TIP and HINT=
forget SSDs with LVM unless of enterprise level
especially if you are going to use/implement the thin pro= visioning

How to identify an SSD of enterprise level:
it costs from 1,00 euro per gigabyte up to 1,50 euro per = gigabyte

Kind regards
Roberto Gini
Technical Manager @ www.RecuperoDatiRAIDFAsTec.it



Il giorno 14 ott 2022, alle ore 21:50, Roger He= flin <rogerhe= flin@gmail.com> ha scritto:
What is the underlying disk hardware you are running th=
is on?
virtual, spinning, ssd, nvme?

On Thu, Oct 13, 2022 at 2:01=
 AM Pawan Sharma <sharmapawan@microsoft.com> wrote:

 adding this to lvm-devel mailing list=
 also.

 Regards,
 Pawan

 From: Pawan Sharma
 Sent: =
Wednesday, October 12, 2022 10:42 PM
 To: linux-lvm@redhat.com <linux=
-lvm@redhat.com>
 Cc: Mitta Sai Chaithanya <mittas@microsoft.com&g=
t;; Kapil Upadhayay <kupadhayay@microsoft.com>
 Subject: LVM2 : pe=
rformance drop even after deleting the snapshot

 Hi Everyone,

 We are evaluating lvm2 snapshots and doing performance testing on it.=
 This is what we are doing :

 dump some data to lvm2 volume (using f=
io)
 take the snapshot
 delete the snapshot (no IOs anywhere after cr=
eating the snapshot)
 run the fio on lvm2 volume

 Here as you can=
 see, we are just creating the snapshot and immediately deleting it. There =
are no IOs to the main volume or anywhere. When we run the fio after this (=
step 4) and we see around 50% drop in performance with reference to the num=
ber we get in step 1.

 It is expected to see a performance drop if t=
here is a snapshot because of the COW. But here we deleted the snapshot, an=
d it is not referring to any data also. We should not see any performance d=
rop here.

 Could someone please help me understand this behavior. Wh=
y are we seeing the performance drop in this case? It seems like we deleted=
 the snapshot but still it is not deleted, and we are paying the COW penalt=
y.

 System Info:

 OS : ubuntu 18.04
 Kernel : 5.4.0
 # lvm version
   LVM version:     2.02.176(2) (2017-11-03)
   Libra=
ry version: 1.02.145 (2017-11-03)
   Driver version:  4.41.0

 We =
also tried on latest ubuntu with newer version of LVM. We got the same beha=
vior.

 Any help/pointers would be appreciated. Thanks in advance.
 Regards,
 Pawan

 linux-lvm mailing list
 linux-lvm@r=
edhat.com
 https://listman.redhat.com/mailman/listinfo/linux-lvm
 read the=
 LVM HOW-TO at http://tldp.org/=
HOWTO/LVM-HOWTO/


linux-lvm mailing list
=
linux-lvm@redhat.com
https://listman.redhat.com/mailman/listinfo/linux-lvmread the LVM HOW-TO at http://=
tldp.org/HOWTO/LVM-HOWTO/

------CF91JKVZ1DVZCB4Q5FIPZ79SHU8Q40-- --===============3968364722874422570== Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Disposition: inline _______________________________________________ linux-lvm mailing list linux-lvm@redhat.com https://listman.redhat.com/mailman/listinfo/linux-lvm read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/ --===============3968364722874422570==--