From: Gionatan Danti <g.danti@assyoma.it>
To: LVM general discussion and development <linux-lvm@redhat.com>
Cc: Zhiyong Ye <yezhiyong@bytedance.com>
Subject: Re: [linux-lvm] Why is the performance of my lvmthin snapshot so poor
Date: Tue, 14 Jun 2022 09:04:02 +0200 [thread overview]
Message-ID: <e779f9dc7139963adfa64b03eca170f3@assyoma.it> (raw)
In-Reply-To: <9c22b11a-b539-1974-7994-6835eea82bfd@bytedance.com>
Il 2022-06-13 10:49 Zhiyong Ye ha scritto:
> The performance degradation after snapshotting is expected as writing
> to a snapshotted lv involving reading the original data, writing it
> elsewhere and then writing new data into the original chunk. But the
> performance loss was so much more than I expected. Is there any way to
> improve performance after creating a snapshot? Can I ask for your
> help?
This is the key point: when first writing to a new chunk, not only it
needs to be allocated, but old data must be copied. This r/m/w operation
transform an async operation (write) on a sync one (read), ruining
performance. Subsequent writes to the same chunk does have the same
issue.
The magnitute of the slowdown seems somewhat excessive, though. When
dealing with HDD pools, I remember a 3-5x impact on IOPs. Can you show
the exact fio command and the parameters of your thin pool (ie: chunk
size) and storage subsystem (HDD vs SSD, SATA vs SAS vs NVME)?
Regards.
--
Danti Gionatan
Supporto Tecnico
Assyoma S.r.l. - www.assyoma.it
email: g.danti@assyoma.it - info@assyoma.it
GPG public key ID: FF5F32A8
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next prev parent reply other threads:[~2022-06-14 7:11 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-06-13 8:49 [linux-lvm] Why is the performance of my lvmthin snapshot so poor Zhiyong Ye
2022-06-14 7:04 ` Gionatan Danti [this message]
2022-06-14 10:16 ` Zhiyong Ye
2022-06-14 12:56 ` Gionatan Danti
2022-06-14 13:29 ` Zhiyong Ye
2022-06-14 14:54 ` Gionatan Danti
2022-06-15 7:42 ` Zhiyong Ye
2022-06-15 9:34 ` Gionatan Danti
2022-06-15 9:46 ` Zhiyong Ye
2022-06-15 12:40 ` Gionatan Danti
2022-06-15 16:39 ` Demi Marie Obenour
2022-06-16 7:53 ` Demi Marie Obenour
2022-06-16 13:22 ` Gionatan Danti
2022-06-16 16:19 ` Demi Marie Obenour
2022-06-16 19:50 ` Gionatan Danti
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