Hi, response inline.
Zitat von "Kyriazis, George" <george.kyriazis@xxxxxxxxx>:
Thank you all.
The cluster is used mostly for backup of large files currently, but
we are hoping to use it for home directories (compiles, etc.) soon.
Most usage would be for large files, though.
What I've observed with its current usage is that ceph rebalances,
and proxmox-initiated VM backups bring the storage to its knees.
Would a safe approach be to move the metadata pool to ssd first, see
how it goes (since it would be cheaper), and then add DB/WAL disks?
Moving the metadata to SSDs first is absolutely reasonable and
relatively cheap since it usually doesn't contain huge amounts of data.
How would ceph behave if we are adding DB/WAL disks "slowly" (ie one
node at a time)? We have about 100 OSDs (mix hdd/ssd) spread across
about 25 hosts. Hosts are server-grade with plenty of memory and
processing power.
The answer is as always "it depends". If you rebuild the OSDs entirely
(host-wise) instead of migrating the DB off to SSDs, you might
encounter slow requests as you already noticed yourself. But the whole
process would be faster than migrating each DB individually.
If you take the migration approach, it would be less invasive, each
OSD would just have to catch up after restart, reducing the load
drastically compared to a rebuild. But then again, it would take way
more time to complete. How large are the OSDs and how much are they
utilized? Do you have some history how long a host rebuild would
usually take?
Thank you!
George
-----Original Message-----
From: Eugen Block <eblock@xxxxxx>
Sent: Wednesday, October 2, 2024 2:18 AM
To: ceph-users@xxxxxxx
Subject: Re: Question about speeding hdd based cluster
Hi George,
the docs [0] strongly recommend to have dedicated SSD or NVMe OSDs for
the metadata pool. You'll also benefit from dedicated DB/WAL devices.
But as Joachim already stated, it depends on a couple of factors like the
number of clients, the load they produce, file sizes etc. There's
no easy answer.
Regards,
Eugen
[0] https://docs.ceph.com/en/latest/cephfs/createfs/#creating-pools
Zitat von Joachim Kraftmayer <joachim.kraftmayer@xxxxxxxxx>:
> Hi Kyriazis,
>
> depends on the workload.
> I would recommend to add ssd/nvme DB/WAL to each osd.
>
>
>
> Joachim Kraftmayer
>
> www.clyso.com
>
> Hohenzollernstr. 27, 80801 Munich
>
> Utting a. A. | HR: Augsburg | HRB: 25866 | USt. ID-Nr.: DE2754306
>
> Kyriazis, George <george.kyriazis@xxxxxxxxx> schrieb am Mi., 2. Okt.
> 2024,
> 07:37:
>
>> Hello ceph-users,
>>
>> I’ve been wondering…. I have a proxmox hdd-based cephfs pool with no
>> DB/WAL drives. I also have ssd drives in this setup used for
other pools.
>>
>> What would increase the speed of the hdd-based cephfs more, and in
>> what usage scenarios:
>>
>> 1. Adding ssd/nvme DB/WAL drives for each node 2. Moving the metadata
>> pool for my cephfs to ssd 3. Increasing the performance of the
>> network. I currently have 10gbe links.
>>
>> It doesn’t look like the network is currently saturated, so I’m
>> thinking
>> (3) is not a solution. However, if I choose any of the other
>> options, would I need to also upgrade the network so that the network
>> does not become a bottleneck?
>>
>> Thank you!
>>
>> George
>>
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