Re: troubleshooting space usage

[Igor Fedotov <ifedotov@xxxxxxx>]

Hi Andrei,

The most obvious reason is space usage overhead caused by BlueStore allocation granularity, e.g. if bluestore_min_alloc_size is 64K  and average object size is 16K one will waste 48K per object in average. This is rather a speculation so far as we lack key the information about your cluster:

- Ceph version

- What are the main devices for OSD: hdd or ssd.

- BlueStore or FileStore.

- average RGW object size.

You might also want to collect and share performance counter dumps (ceph daemon osd.N perf dump) and "ceph osd df tree" reports from a couple of your OSDs.

Thanks,

Igor

On 7/2/2019 11:43 AM, Andrei Mikhailovsky wrote:

Bump!

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From: "Andrei Mikhailovsky" <andrei@xxxxxxxxxx>
To: "ceph-users" <ceph-users@xxxxxxxxxxxxxx>
Sent: Friday, 28 June, 2019 14:54:53
Subject: troubleshooting space usage

Hi

Could someone please explain / show how to troubleshoot the space usage in Ceph and how to reclaim the unused space?

I have a small cluster with 40 osds, replica of 2, mainly used as a backend for cloud stack as well as the S3 gateway. The used space doesn't make any sense to me, especially the rgw pool, so I am seeking help.

Here is what I found from the client:

Ceph -s shows the

 usage:   89 TiB used, 24 TiB / 113 TiB avail

Ceph df shows:

Primary-ubuntu-1               5       27 TiB     90.11       3.0 TiB     7201098

Primary-ubuntu-1-ssd           57     1.2 TiB     89.62       143 GiB      359260   

.rgw.buckets                   19      15 TiB     83.73       3.0 TiB     8742222

the usage of the Primary-ubuntu-1 and Primary-ubuntu-1-ssd is in line with my expectations. However, the .rgw.buckets pool seems to be using way too much. The usage of all rgw buckets shows 6.5TB usage (looking at the size_kb values from the "radosgw-admin bucket stats"). I am trying to figure out why .rgw.buckets is using 15TB of space instead of the 6.5TB as shown from the bucket usage. 

Thanks

Andrei

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