What you want to do is to stop the OSD (and all its copies of data it contains) by stopping the OSD service immediately. The downside of this approach is it causes the PGs on that OSD to be degraded. But the upside is the OSD which has bad hardware is immediately no longer participating in any client IO (the source of your RGW 503s). In this situation the PGs go into degraded+backfilling The alternative method is to keep the failing OSD up and in the cluster but slowly migrate the data off of it, this would be a long drawn out period of time in which the failing disk would continue to serve client reads and also facilitate backfill but you wouldnt take a copy of the data out of the cluster and cause degraded PGs. In this scenario the PGs would be remapped+backfilling I tried to find a way to have your cake and eat it to in relation to this "predicament" in this tracker issue: https://tracker.ceph.com/issues/44400 but it was deemed "wont fix". Respectfully, *Wes Dillingham* LinkedIn <http://www.linkedin.com/in/wesleydillingham> wes@wesdillingham.com On Fri, Apr 26, 2024 at 11:25 AM Mary Zhang <maryzhang0920@gmail.com> wrote:

Thank you Eugen for your warm help!

I'm trying to understand the difference between 2 methods. For method 1, or "ceph orch osd rm osd_id", OSD Service — Ceph Documentation <https://docs.ceph.com/en/latest/cephadm/services/osd/#remove-an-osd> says it involves 2 steps:

1.

evacuating all placement groups (PGs) from the OSD 2.

removing the PG-free OSD from the cluster

For method 2, or the procedure you recommended, Adding/Removing OSDs — Ceph Documentation < https://docs.ceph.com/en/latest/rados/operations/add-or-rm-osds/#removing-os...

...

says "After the OSD has been taken out of the cluster, Ceph begins rebalancing the cluster by migrating placement groups out of the OSD that was removed. "

What's the difference between "evacuating PGs" in method 1 and "migrating PGs" in method 2? I think method 1 must read the OSD to be removed. Otherwise, we would not see slow ops warning. Does method 2 not involve reading this OSD?

Thanks, Mary

On Fri, Apr 26, 2024 at 5:15 AM Eugen Block <eblock@nde.ag> wrote:

...

Hi,

if you remove the OSD this way, it will be drained. Which means that it will try to recover PGs from this OSD, and in case of hardware failure it might lead to slow requests. It might make sense to forcefully remove the OSD without draining:

- stop the osd daemon - mark it as out - osd purge <id|osd.id> [--force] [--yes-i-really-mean-it]

Regards, Eugen

Zitat von Mary Zhang <maryzhang0920@gmail.com>:

...

Hi,

We recently removed an osd from our Cepth cluster. Its underlying disk has a hardware issue.

We use command: ceph orch osd rm osd_id --zap

During the process, sometimes ceph cluster enters warning state with slow ops on this osd. Our rgw also failed to respond to requests and returned 503.

We restarted rgw daemon to make it work again. But the same failure occured from time to time. Eventually we noticed that rgw 503 error is a result of osd slow ops.

Our cluster has 18 hosts and 210 OSDs. We expect remove an osd with hardware issue won't impact cluster performance & rgw availbility. Is our expectation reasonable? What's the best way to handle osd with hardware failures?

Thank you in advance for any comments or suggestions.

Best Regards, Mary Zhang _______________________________________________ ceph-users mailing list -- ceph-users@ceph.io To unsubscribe send an email to ceph-users-leave@ceph.io

_______________________________________________ ceph-users mailing list -- ceph-users@ceph.io To unsubscribe send an email to ceph-users-leave@ceph.io

_______________________________________________ ceph-users mailing list -- ceph-users@ceph.io To unsubscribe send an email to ceph-users-leave@ceph.io

If the rest of the cluster is healthy and your resiliency is configured properly, for example to sustain the loss of one or more hosts at a time, you don’t need to worry about a single disk. Just take it out and remove it (forcefully) so it doesn’t have any clients anymore. Ceph will immediately assign different primary OSDs and your clients will be happy again. ;-) Zitat von Mary Zhang <maryzhang0920@gmail.com>:

Thank you Wesley for the clear explanation between the 2 methods! The tracker issue you mentioned https://tracker.ceph.com/issues/44400 talks about primary-affinity. Could primary-affinity help remove an OSD with hardware issue from the cluster gracefully?

Thanks, Mary

On Fri, Apr 26, 2024 at 8:43 AM Wesley Dillingham <wes@wesdillingham.com> wrote:

...

What you want to do is to stop the OSD (and all its copies of data it contains) by stopping the OSD service immediately. The downside of this approach is it causes the PGs on that OSD to be degraded. But the upside is the OSD which has bad hardware is immediately no longer participating in any client IO (the source of your RGW 503s). In this situation the PGs go into degraded+backfilling

The alternative method is to keep the failing OSD up and in the cluster but slowly migrate the data off of it, this would be a long drawn out period of time in which the failing disk would continue to serve client reads and also facilitate backfill but you wouldnt take a copy of the data out of the cluster and cause degraded PGs. In this scenario the PGs would be remapped+backfilling

I tried to find a way to have your cake and eat it to in relation to this "predicament" in this tracker issue: https://tracker.ceph.com/issues/44400 but it was deemed "wont fix".

Respectfully,

*Wes Dillingham* LinkedIn <http://www.linkedin.com/in/wesleydillingham> wes@wesdillingham.com

On Fri, Apr 26, 2024 at 11:25 AM Mary Zhang <maryzhang0920@gmail.com> wrote:

...

Thank you Eugen for your warm help!

I'm trying to understand the difference between 2 methods. For method 1, or "ceph orch osd rm osd_id", OSD Service — Ceph Documentation <https://docs.ceph.com/en/latest/cephadm/services/osd/#remove-an-osd> says it involves 2 steps:

1.

evacuating all placement groups (PGs) from the OSD 2.

removing the PG-free OSD from the cluster

For method 2, or the procedure you recommended, Adding/Removing OSDs — Ceph Documentation < https://docs.ceph.com/en/latest/rados/operations/add-or-rm-osds/#removing-os...

...

says "After the OSD has been taken out of the cluster, Ceph begins rebalancing the cluster by migrating placement groups out of the OSD that was removed. "

What's the difference between "evacuating PGs" in method 1 and "migrating PGs" in method 2? I think method 1 must read the OSD to be removed. Otherwise, we would not see slow ops warning. Does method 2 not involve reading this OSD?

Thanks, Mary

On Fri, Apr 26, 2024 at 5:15 AM Eugen Block <eblock@nde.ag> wrote:

...

Hi,

if you remove the OSD this way, it will be drained. Which means that it will try to recover PGs from this OSD, and in case of hardware failure it might lead to slow requests. It might make sense to forcefully remove the OSD without draining:

- stop the osd daemon - mark it as out - osd purge <id|osd.id> [--force] [--yes-i-really-mean-it]

Regards, Eugen

Zitat von Mary Zhang <maryzhang0920@gmail.com>:

...

Hi,

We recently removed an osd from our Cepth cluster. Its underlying disk has a hardware issue.

We use command: ceph orch osd rm osd_id --zap

During the process, sometimes ceph cluster enters warning state with slow ops on this osd. Our rgw also failed to respond to requests and returned 503.

We restarted rgw daemon to make it work again. But the same failure occured from time to time. Eventually we noticed that rgw 503 error is a result of osd slow ops.

Our cluster has 18 hosts and 210 OSDs. We expect remove an osd with hardware issue won't impact cluster performance & rgw availbility. Is our expectation reasonable? What's the best way to handle osd with hardware failures?

Thank you in advance for any comments or suggestions.

Best Regards, Mary Zhang _______________________________________________ ceph-users mailing list -- ceph-users@ceph.io To unsubscribe send an email to ceph-users-leave@ceph.io

_______________________________________________ ceph-users mailing list -- ceph-users@ceph.io To unsubscribe send an email to ceph-users-leave@ceph.io

_______________________________________________ ceph-users mailing list -- ceph-users@ceph.io To unsubscribe send an email to ceph-users-leave@ceph.io

Hi all, I second Eugen's recommendation. We have a cluster with large HDD OSDs where the following timings are found: - drain an OSD: 2 weeks. - down an OSD and let cluster recover: 6 hours. The drain OSD procedure is - in my experience - a complete waste of time, actually puts your cluster at higher risk of a second failure (its not guaranteed that the bad PG(s) is/are drained first) and also screws up all sorts of internal operations like scrub etc for an unnecessarily long time. The recovery procedure is much faster, because it uses all-to-all recovery while drain is limited to no more than max_backfills PGs at a time and your broken disk sits much longer in the cluster. On SSDs the "down OSD"-method shows a similar speed-up factor. For a security measure, don't destroy the OSD right away, wait for recovery to complete and only then destroy the OSD and throw away the disk. In case an error occurs during recovery, you can almost always still export PGs from a failed disk and inject it back into the cluster. This, however, requires to take disks out as soon as they show problems and before they fail hard. Keep a little bit of life time to have a chance to recover data. Look at the manual of ddrescue why it is important to stop IO from a failing disk as soon as possible. Best regards, ================= Frank Schilder AIT Risø Campus Bygning 109, rum S14 ________________________________________ From: Eugen Block <eblock@nde.ag> Sent: Saturday, April 27, 2024 10:29 AM To: Mary Zhang Cc: ceph-users@ceph.io; Wesley Dillingham Subject: [ceph-users] Re: Remove an OSD with hardware issue caused rgw 503 If the rest of the cluster is healthy and your resiliency is configured properly, for example to sustain the loss of one or more hosts at a time, you don’t need to worry about a single disk. Just take it out and remove it (forcefully) so it doesn’t have any clients anymore. Ceph will immediately assign different primary OSDs and your clients will be happy again. ;-) Zitat von Mary Zhang <maryzhang0920@gmail.com>:

Thank you Wesley for the clear explanation between the 2 methods! The tracker issue you mentioned https://tracker.ceph.com/issues/44400 talks about primary-affinity. Could primary-affinity help remove an OSD with hardware issue from the cluster gracefully?

Thanks, Mary

On Fri, Apr 26, 2024 at 8:43 AM Wesley Dillingham <wes@wesdillingham.com> wrote:

...

What you want to do is to stop the OSD (and all its copies of data it contains) by stopping the OSD service immediately. The downside of this approach is it causes the PGs on that OSD to be degraded. But the upside is the OSD which has bad hardware is immediately no longer participating in any client IO (the source of your RGW 503s). In this situation the PGs go into degraded+backfilling

The alternative method is to keep the failing OSD up and in the cluster but slowly migrate the data off of it, this would be a long drawn out period of time in which the failing disk would continue to serve client reads and also facilitate backfill but you wouldnt take a copy of the data out of the cluster and cause degraded PGs. In this scenario the PGs would be remapped+backfilling

I tried to find a way to have your cake and eat it to in relation to this "predicament" in this tracker issue: https://tracker.ceph.com/issues/44400 but it was deemed "wont fix".

Respectfully,

*Wes Dillingham* LinkedIn <http://www.linkedin.com/in/wesleydillingham> wes@wesdillingham.com

On Fri, Apr 26, 2024 at 11:25 AM Mary Zhang <maryzhang0920@gmail.com> wrote:

...

Thank you Eugen for your warm help!

I'm trying to understand the difference between 2 methods. For method 1, or "ceph orch osd rm osd_id", OSD Service — Ceph Documentation <https://docs.ceph.com/en/latest/cephadm/services/osd/#remove-an-osd> says it involves 2 steps:

1.

evacuating all placement groups (PGs) from the OSD 2.

removing the PG-free OSD from the cluster

For method 2, or the procedure you recommended, Adding/Removing OSDs — Ceph Documentation < https://docs.ceph.com/en/latest/rados/operations/add-or-rm-osds/#removing-os...

...

says "After the OSD has been taken out of the cluster, Ceph begins rebalancing the cluster by migrating placement groups out of the OSD that was removed. "

What's the difference between "evacuating PGs" in method 1 and "migrating PGs" in method 2? I think method 1 must read the OSD to be removed. Otherwise, we would not see slow ops warning. Does method 2 not involve reading this OSD?

Thanks, Mary

On Fri, Apr 26, 2024 at 5:15 AM Eugen Block <eblock@nde.ag> wrote:

...

Hi,

if you remove the OSD this way, it will be drained. Which means that it will try to recover PGs from this OSD, and in case of hardware failure it might lead to slow requests. It might make sense to forcefully remove the OSD without draining:

- stop the osd daemon - mark it as out - osd purge <id|osd.id> [--force] [--yes-i-really-mean-it]

Regards, Eugen

Zitat von Mary Zhang <maryzhang0920@gmail.com>:

...

Hi,

We recently removed an osd from our Cepth cluster. Its underlying disk has a hardware issue.

We use command: ceph orch osd rm osd_id --zap

During the process, sometimes ceph cluster enters warning state with slow ops on this osd. Our rgw also failed to respond to requests and returned 503.

We restarted rgw daemon to make it work again. But the same failure occured from time to time. Eventually we noticed that rgw 503 error is a result of osd slow ops.

Our cluster has 18 hosts and 210 OSDs. We expect remove an osd with hardware issue won't impact cluster performance & rgw availbility. Is our expectation reasonable? What's the best way to handle osd with hardware failures?

Thank you in advance for any comments or suggestions.

Best Regards, Mary Zhang _______________________________________________ ceph-users mailing list -- ceph-users@ceph.io To unsubscribe send an email to ceph-users-leave@ceph.io

_______________________________________________ ceph-users mailing list -- ceph-users@ceph.io To unsubscribe send an email to ceph-users-leave@ceph.io

_______________________________________________ ceph-users mailing list -- ceph-users@ceph.io To unsubscribe send an email to ceph-users-leave@ceph.io

_______________________________________________ ceph-users mailing list -- ceph-users@ceph.io To unsubscribe send an email to ceph-users-leave@ceph.io

I think you are panicking way too much. Chances are that you will never need that command, so don't get fussed out by an old post. Just follow what I wrote and, in the extremely rare case that recovery does not complete due to missing information, send an e-mail to this list and state that you still have the disk of the down OSD. Someone will send you the export/import commands within a short time. So stop worrying and just administrate your cluster with common storage admin sense. Best regards, ================= Frank Schilder AIT Risø Campus Bygning 109, rum S14 ________________________________________ From: Mary Zhang <maryzhang0920@gmail.com> Sent: Tuesday, April 30, 2024 5:00 PM To: Frank Schilder Cc: Eugen Block; ceph-users@ceph.io; Wesley Dillingham Subject: Re: [ceph-users] Re: Remove an OSD with hardware issue caused rgw 503 Thank you Frank for sharing such valuable experience! I really appreciate it. We observe similar timelines: it took more than 1 week to drain our OSD. Regarding export PGs from failed disk and inject it back to the cluster, do you have any documentations? I find this online Ceph.io — Incomplete PGs -- OH MY!<https://ceph.io/en/news/blog/2015/incomplete-pgs-oh-my/>, but not sure whether it's the standard process. Thanks, Mary On Tue, Apr 30, 2024 at 3:27 AM Frank Schilder <frans@dtu.dk<mailto:frans@dtu.dk>> wrote: Hi all, I second Eugen's recommendation. We have a cluster with large HDD OSDs where the following timings are found: - drain an OSD: 2 weeks. - down an OSD and let cluster recover: 6 hours. The drain OSD procedure is - in my experience - a complete waste of time, actually puts your cluster at higher risk of a second failure (its not guaranteed that the bad PG(s) is/are drained first) and also screws up all sorts of internal operations like scrub etc for an unnecessarily long time. The recovery procedure is much faster, because it uses all-to-all recovery while drain is limited to no more than max_backfills PGs at a time and your broken disk sits much longer in the cluster. On SSDs the "down OSD"-method shows a similar speed-up factor. For a security measure, don't destroy the OSD right away, wait for recovery to complete and only then destroy the OSD and throw away the disk. In case an error occurs during recovery, you can almost always still export PGs from a failed disk and inject it back into the cluster. This, however, requires to take disks out as soon as they show problems and before they fail hard. Keep a little bit of life time to have a chance to recover data. Look at the manual of ddrescue why it is important to stop IO from a failing disk as soon as possible. Best regards, ================= Frank Schilder AIT Risø Campus Bygning 109, rum S14 ________________________________________ From: Eugen Block <eblock@nde.ag<mailto:eblock@nde.ag>> Sent: Saturday, April 27, 2024 10:29 AM To: Mary Zhang Cc: ceph-users@ceph.io<mailto:ceph-users@ceph.io>; Wesley Dillingham Subject: [ceph-users] Re: Remove an OSD with hardware issue caused rgw 503 If the rest of the cluster is healthy and your resiliency is configured properly, for example to sustain the loss of one or more hosts at a time, you don’t need to worry about a single disk. Just take it out and remove it (forcefully) so it doesn’t have any clients anymore. Ceph will immediately assign different primary OSDs and your clients will be happy again. ;-) Zitat von Mary Zhang <maryzhang0920@gmail.com<mailto:maryzhang0920@gmail.com>>:

Thank you Wesley for the clear explanation between the 2 methods! The tracker issue you mentioned https://tracker.ceph.com/issues/44400 talks about primary-affinity. Could primary-affinity help remove an OSD with hardware issue from the cluster gracefully?

Thanks, Mary

On Fri, Apr 26, 2024 at 8:43 AM Wesley Dillingham <wes@wesdillingham.com<mailto:wes@wesdillingham.com>> wrote:

...

What you want to do is to stop the OSD (and all its copies of data it contains) by stopping the OSD service immediately. The downside of this approach is it causes the PGs on that OSD to be degraded. But the upside is the OSD which has bad hardware is immediately no longer participating in any client IO (the source of your RGW 503s). In this situation the PGs go into degraded+backfilling

The alternative method is to keep the failing OSD up and in the cluster but slowly migrate the data off of it, this would be a long drawn out period of time in which the failing disk would continue to serve client reads and also facilitate backfill but you wouldnt take a copy of the data out of the cluster and cause degraded PGs. In this scenario the PGs would be remapped+backfilling

I tried to find a way to have your cake and eat it to in relation to this "predicament" in this tracker issue: https://tracker.ceph.com/issues/44400 but it was deemed "wont fix".

Respectfully,

*Wes Dillingham* LinkedIn <http://www.linkedin.com/in/wesleydillingham> wes@wesdillingham.com<mailto:wes@wesdillingham.com>

On Fri, Apr 26, 2024 at 11:25 AM Mary Zhang <maryzhang0920@gmail.com<mailto:maryzhang0920@gmail.com>> wrote:

...

Thank you Eugen for your warm help!

I'm trying to understand the difference between 2 methods. For method 1, or "ceph orch osd rm osd_id", OSD Service — Ceph Documentation <https://docs.ceph.com/en/latest/cephadm/services/osd/#remove-an-osd> says it involves 2 steps:

1.

evacuating all placement groups (PGs) from the OSD 2.

removing the PG-free OSD from the cluster

For method 2, or the procedure you recommended, Adding/Removing OSDs — Ceph Documentation < https://docs.ceph.com/en/latest/rados/operations/add-or-rm-osds/#removing-os...

...

says "After the OSD has been taken out of the cluster, Ceph begins rebalancing the cluster by migrating placement groups out of the OSD that was removed. "

What's the difference between "evacuating PGs" in method 1 and "migrating PGs" in method 2? I think method 1 must read the OSD to be removed. Otherwise, we would not see slow ops warning. Does method 2 not involve reading this OSD?

Thanks, Mary

On Fri, Apr 26, 2024 at 5:15 AM Eugen Block <eblock@nde.ag<mailto:eblock@nde.ag>> wrote:

...

Hi,

if you remove the OSD this way, it will be drained. Which means that it will try to recover PGs from this OSD, and in case of hardware failure it might lead to slow requests. It might make sense to forcefully remove the OSD without draining:

- stop the osd daemon - mark it as out - osd purge <id|osd.id<http://osd.id>> [--force] [--yes-i-really-mean-it]

Regards, Eugen

Zitat von Mary Zhang <maryzhang0920@gmail.com<mailto:maryzhang0920@gmail.com>>:

...

Hi,

We recently removed an osd from our Cepth cluster. Its underlying disk has a hardware issue.

We use command: ceph orch osd rm osd_id --zap

During the process, sometimes ceph cluster enters warning state with slow ops on this osd. Our rgw also failed to respond to requests and returned 503.

We restarted rgw daemon to make it work again. But the same failure occured from time to time. Eventually we noticed that rgw 503 error is a result of osd slow ops.

Our cluster has 18 hosts and 210 OSDs. We expect remove an osd with hardware issue won't impact cluster performance & rgw availbility. Is our expectation reasonable? What's the best way to handle osd with hardware failures?

Thank you in advance for any comments or suggestions.

Best Regards, Mary Zhang _______________________________________________ ceph-users mailing list -- ceph-users@ceph.io<mailto:ceph-users@ceph.io> To unsubscribe send an email to ceph-users-leave@ceph.io<mailto:ceph-users-leave@ceph.io>

_______________________________________________ ceph-users mailing list -- ceph-users@ceph.io<mailto:ceph-users@ceph.io> To unsubscribe send an email to ceph-users-leave@ceph.io<mailto:ceph-users-leave@ceph.io>

_______________________________________________ ceph-users mailing list -- ceph-users@ceph.io<mailto:ceph-users@ceph.io> To unsubscribe send an email to ceph-users-leave@ceph.io<mailto:ceph-users-leave@ceph.io>

_______________________________________________ ceph-users mailing list -- ceph-users@ceph.io<mailto:ceph-users@ceph.io> To unsubscribe send an email to ceph-users-leave@ceph.io<mailto:ceph-users-leave@ceph.io>

Sorry Frank, I typed the wrong name. On Tue, Apr 30, 2024, 8:51 AM Mary Zhang <maryzhang0920@gmail.com> wrote:

Sounds good. Thank you Kevin and have a nice day!

Best Regards, Mary

On Tue, Apr 30, 2024, 8:21 AM Frank Schilder <frans@dtu.dk> wrote:

...

I think you are panicking way too much. Chances are that you will never need that command, so don't get fussed out by an old post.

Just follow what I wrote and, in the extremely rare case that recovery does not complete due to missing information, send an e-mail to this list and state that you still have the disk of the down OSD. Someone will send you the export/import commands within a short time.

So stop worrying and just administrate your cluster with common storage admin sense.

Best regards, ================= Frank Schilder AIT Risø Campus Bygning 109, rum S14

________________________________________ From: Mary Zhang <maryzhang0920@gmail.com> Sent: Tuesday, April 30, 2024 5:00 PM To: Frank Schilder Cc: Eugen Block; ceph-users@ceph.io; Wesley Dillingham Subject: Re: [ceph-users] Re: Remove an OSD with hardware issue caused rgw 503

Thank you Frank for sharing such valuable experience! I really appreciate it. We observe similar timelines: it took more than 1 week to drain our OSD. Regarding export PGs from failed disk and inject it back to the cluster, do you have any documentations? I find this online Ceph.io — Incomplete PGs -- OH MY!<https://ceph.io/en/news/blog/2015/incomplete-pgs-oh-my/>, but not sure whether it's the standard process.

Thanks, Mary

On Tue, Apr 30, 2024 at 3:27 AM Frank Schilder <frans@dtu.dk<mailto: frans@dtu.dk>> wrote: Hi all,

I second Eugen's recommendation. We have a cluster with large HDD OSDs where the following timings are found:

- drain an OSD: 2 weeks. - down an OSD and let cluster recover: 6 hours.

The drain OSD procedure is - in my experience - a complete waste of time, actually puts your cluster at higher risk of a second failure (its not guaranteed that the bad PG(s) is/are drained first) and also screws up all sorts of internal operations like scrub etc for an unnecessarily long time. The recovery procedure is much faster, because it uses all-to-all recovery while drain is limited to no more than max_backfills PGs at a time and your broken disk sits much longer in the cluster.

On SSDs the "down OSD"-method shows a similar speed-up factor.

For a security measure, don't destroy the OSD right away, wait for recovery to complete and only then destroy the OSD and throw away the disk. In case an error occurs during recovery, you can almost always still export PGs from a failed disk and inject it back into the cluster. This, however, requires to take disks out as soon as they show problems and before they fail hard. Keep a little bit of life time to have a chance to recover data. Look at the manual of ddrescue why it is important to stop IO from a failing disk as soon as possible.

Best regards, ================= Frank Schilder AIT Risø Campus Bygning 109, rum S14

________________________________________ From: Eugen Block <eblock@nde.ag<mailto:eblock@nde.ag>> Sent: Saturday, April 27, 2024 10:29 AM To: Mary Zhang Cc: ceph-users@ceph.io<mailto:ceph-users@ceph.io>; Wesley Dillingham Subject: [ceph-users] Re: Remove an OSD with hardware issue caused rgw 503

If the rest of the cluster is healthy and your resiliency is configured properly, for example to sustain the loss of one or more hosts at a time, you don’t need to worry about a single disk. Just take it out and remove it (forcefully) so it doesn’t have any clients anymore. Ceph will immediately assign different primary OSDs and your clients will be happy again. ;-)

Zitat von Mary Zhang <maryzhang0920@gmail.com<mailto: maryzhang0920@gmail.com>>:

...

Thank you Wesley for the clear explanation between the 2 methods! The tracker issue you mentioned https://tracker.ceph.com/issues/44400 talks about primary-affinity. Could primary-affinity help remove an OSD with hardware issue from the cluster gracefully?

Thanks, Mary

On Fri, Apr 26, 2024 at 8:43 AM Wesley Dillingham < wes@wesdillingham.com<mailto:wes@wesdillingham.com>> wrote:

...

What you want to do is to stop the OSD (and all its copies of data it contains) by stopping the OSD service immediately. The downside of this approach is it causes the PGs on that OSD to be degraded. But the upside is the OSD which has bad hardware is immediately no longer participating in any client IO (the source of your RGW 503s). In this situation the PGs go into degraded+backfilling

The alternative method is to keep the failing OSD up and in the cluster but slowly migrate the data off of it, this would be a long drawn out period of time in which the failing disk would continue to serve client reads and also facilitate backfill but you wouldnt take a copy of the data out of the cluster and cause degraded PGs. In this scenario the PGs would be remapped+backfilling

I tried to find a way to have your cake and eat it to in relation to this "predicament" in this tracker issue: https://tracker.ceph.com/issues/44400 but it was deemed "wont fix".

Respectfully,

*Wes Dillingham* LinkedIn <http://www.linkedin.com/in/wesleydillingham> wes@wesdillingham.com<mailto:wes@wesdillingham.com>

On Fri, Apr 26, 2024 at 11:25 AM Mary Zhang <maryzhang0920@gmail.com <mailto:maryzhang0920@gmail.com>> wrote:

...

Thank you Eugen for your warm help!

I'm trying to understand the difference between 2 methods. For method 1, or "ceph orch osd rm osd_id", OSD Service — Ceph Documentation <https://docs.ceph.com/en/latest/cephadm/services/osd/#remove-an-osd> says it involves 2 steps:

1.

evacuating all placement groups (PGs) from the OSD 2.

removing the PG-free OSD from the cluster

For method 2, or the procedure you recommended, Adding/Removing OSDs — Ceph Documentation <

https://docs.ceph.com/en/latest/rados/operations/add-or-rm-osds/#removing-os...

...

...

says "After the OSD has been taken out of the cluster, Ceph begins rebalancing the cluster by migrating placement groups out of the OSD that was removed. "

What's the difference between "evacuating PGs" in method 1 and "migrating PGs" in method 2? I think method 1 must read the OSD to be removed. Otherwise, we would not see slow ops warning. Does method 2 not involve reading this OSD?

Thanks, Mary

On Fri, Apr 26, 2024 at 5:15 AM Eugen Block <eblock@nde.ag<mailto: eblock@nde.ag>> wrote:

...

Hi,

if you remove the OSD this way, it will be drained. Which means that it will try to recover PGs from this OSD, and in case of hardware failure it might lead to slow requests. It might make sense to forcefully remove the OSD without draining:

- stop the osd daemon - mark it as out - osd purge <id|osd.id<http://osd.id>> [--force] [--yes-i-really-mean-it]

Regards, Eugen

Zitat von Mary Zhang <maryzhang0920@gmail.com<mailto: maryzhang0920@gmail.com>>:

> Hi, > > We recently removed an osd from our Cepth cluster. Its underlying disk has > a hardware issue. > > We use command: ceph orch osd rm osd_id --zap > > During the process, sometimes ceph cluster enters warning state with slow > ops on this osd. Our rgw also failed to respond to requests and returned > 503. > > We restarted rgw daemon to make it work again. But the same failure occured > from time to time. Eventually we noticed that rgw 503 error is a result of > osd slow ops. > > Our cluster has 18 hosts and 210 OSDs. We expect remove an osd with > hardware issue won't impact cluster performance & rgw availbility. Is our > expectation reasonable? What's the best way to handle osd with hardware > failures? > > Thank you in advance for any comments or suggestions. > > Best Regards, > Mary Zhang > _______________________________________________ > ceph-users mailing list -- ceph-users@ceph.io<mailto: ceph-users@ceph.io> > To unsubscribe send an email to ceph-users-leave@ceph.io<mailto: ceph-users-leave@ceph.io>

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