Cache=writeback is perfectly safe, it's flushed when the guest calls fsync, so
journaled filesystems and databases don't lose data that's committed to the
journal.
25 июля 2019 г. 2:28:26 GMT+03:00, Stuart Longland <stua...@longlandclan.id.au>
пишет:
>On 25/7/19 9:01 am, vita...@yourcmc.ru wrote:
>>> 60 millibits per second? 60 bits every 1000 seconds? Are you
>serious?
>>> Or did we get the capitalisation wrong?
>>>
>>> Assuming 60MB/sec (as 60 Mb/sec would still be slower than the
>5MB/sec I
>>> was getting), maybe there's some characteristic that Bluestore is
>>> particularly dependent on regarding the HDDs.
>>>
>>> I'll admit right up front the drives I'm using were chosen because
>they
>>> were all I could get with a 2TB storage capacity for a reasonable
>price.
>>>
>>> I'm not against moving to Bluestore, however, I think I need to
>research
>>> it better to understand why the performance I was getting before was
>so
>>> poor.
>>
>> It's a nano-ceph! So millibits :) I mean 60 megabytes per second, of
>> course. My drives are also crap. I just want to say that you probably
>
>> miss some option for your VM, for example "cache=writeback".
>
>cache=writeback should have no effect on read performance but could be
>quite dangerous if the VM host were to go down immediately after a
>write
>for any reason.
>
>While 60MB/sec is getting respectable, doing so at the cost of data
>safety is not something I'm keen on.
>--
>Stuart Longland (aka Redhatter, VK4MSL)
>
>I haven't lost my mind...
> ...it's backed up on a tape somewhere.
--
With best regards,
Vitaliy Filippov
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