[ceph-users] Drive for Wal and Db

Robert Stanford rstanford8896 at gmail.com
Mon Oct 22 13:13:47 PDT 2018


 We're out of sync, I think.  You have your DB on your data disk so your
block.db symlink points to that disk, right?  There is however no wal
symlink?  So how would you verify your WAL actually lived on your NVMe?

On Mon, Oct 22, 2018 at 3:07 PM David Turner <drakonstein at gmail.com> wrote:

> And by the data disk I mean that I didn't specify a location for the DB
> partition.
>
> On Mon, Oct 22, 2018 at 4:06 PM David Turner <drakonstein at gmail.com>
> wrote:
>
>> Track down where it says they point to?  Does it match what you expect?
>> It does for me.  I have my DB on my data disk and my WAL on a separate NVMe.
>>
>> On Mon, Oct 22, 2018 at 3:21 PM Robert Stanford <rstanford8896 at gmail.com>
>> wrote:
>>
>>>
>>>  David - is it ensured that wal and db both live where the symlink
>>> block.db points?  I assumed that was a symlink for the db, but necessarily
>>> for the wal, because it can live in a place different than the db.
>>>
>>> On Mon, Oct 22, 2018 at 2:18 PM David Turner <drakonstein at gmail.com>
>>> wrote:
>>>
>>>> You can always just go to /var/lib/ceph/osd/ceph-{osd-num}/ and look at
>>>> where the symlinks for block and block.wal point to.
>>>>
>>>> On Mon, Oct 22, 2018 at 12:29 PM Robert Stanford <
>>>> rstanford8896 at gmail.com> wrote:
>>>>
>>>>>
>>>>>  That's what they say, however I did exactly this and my cluster
>>>>> utilization is higher than the total pool utilization by about the number
>>>>> of OSDs * wal size.  I want to verify that the wal is on the SSDs too but
>>>>> I've asked here and no one seems to know a way to verify this.  Do you?
>>>>>
>>>>>  Thank you, R
>>>>>
>>>>> On Mon, Oct 22, 2018 at 5:22 AM Maged Mokhtar <mmokhtar at petasan.org>
>>>>> wrote:
>>>>>
>>>>>>
>>>>>> If you specify a db on ssd and data on hdd and not explicitly specify
>>>>>> a
>>>>>> device for wal, wal will be placed on same ssd partition with db.
>>>>>> Placing only wal on ssd or creating separate devices for wal and db
>>>>>> are
>>>>>> less common setups.
>>>>>>
>>>>>> /Maged
>>>>>>
>>>>>> On 22/10/18 09:03, Fyodor Ustinov wrote:
>>>>>> > Hi!
>>>>>> >
>>>>>> > For sharing SSD between WAL and DB what should be placed on SSD?
>>>>>> WAL or DB?
>>>>>> >
>>>>>> > ----- Original Message -----
>>>>>> > From: "Maged Mokhtar" <mmokhtar at petasan.org>
>>>>>> > To: "ceph-users" <ceph-users at lists.ceph.com>
>>>>>> > Sent: Saturday, 20 October, 2018 20:05:44
>>>>>> > Subject: Re: [ceph-users] Drive for Wal and Db
>>>>>> >
>>>>>> > On 20/10/18 18:57, Robert Stanford wrote:
>>>>>> >
>>>>>> >
>>>>>> >
>>>>>> >
>>>>>> > Our OSDs are BlueStore and are on regular hard drives. Each OSD has
>>>>>> a partition on an SSD for its DB. Wal is on the regular hard drives. Should
>>>>>> I move the wal to share the SSD with the DB?
>>>>>> >
>>>>>> > Regards
>>>>>> > R
>>>>>> >
>>>>>> >
>>>>>> > _______________________________________________
>>>>>> > ceph-users mailing list [ mailto:ceph-users at lists.ceph.com |
>>>>>> ceph-users at lists.ceph.com ] [
>>>>>> http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com |
>>>>>> http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com ]
>>>>>> >
>>>>>> > you should put wal on the faster device, wal and db could share the
>>>>>> same ssd partition,
>>>>>> >
>>>>>> > Maged
>>>>>> >
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>>>>> _______________________________________________
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>>>>
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