[zfs-discuss] windows on thin provision zvol: how to force trim?

Gordan Bobic gordan.bobic at gmail.com
Tue Oct 15 08:38:17 EDT 2013


That's what I use on my VMs. You might also find it is better to use
compression on the client end than on the ZFS side. That way your ZFS
storage box doesn't take the CPU hit for all of the compression going
to/from the FS, plus you get less bandwidth saturation on your interconnect
between the storage and the VM. For my Windows VMs I use NTFS compression
and ZLE on the ZFS side. Just make sure that the disk scrubbing sdelete
performs isn't subject to ntfs compression or you might find that for the
purpose of the scrub your storage suddenly becomes infinite. :)


On Tue, Oct 15, 2013 at 1:33 PM, Ivan Krutskikh <stein.hak at gmail.com> wrote:

> Okay, one promissing solution is to use sdelete from microsoft ( original
> post http://nex7.blogspot.ru/2013/03/zvol-used-space.html), which would
> zero-out all unused space on a zvol. However, this seams write-intensive.
> I'll test this solution and report the results
>
>
> 2013/10/15 Gordan Bobic <gordan.bobic at gmail.com>
>
>> So don't overbook. If your pool gets to 100% full you are going to have
>> major performance issues due to fragmentation anyway. Filling it up from
>> 95% to 100% is likely to be so slow it'll give you ample time (days) to go
>> and delete some snapshots or similar to free up some space.
>>
>>
>> On Tue, Oct 15, 2013 at 1:12 PM, Ivan Krutskikh <stein.hak at gmail.com>wrote:
>>
>>> My concern is resilvering time for a server full of zvol's and clones
>>>
>>> I already use lz4, but once the zvol goes full 100%- It does not shink
>>> back to original, even if the data is already deleted from the filesystem
>>>
>>>
>>> 2013/10/15 Gordan Bobic <gordan.bobic at gmail.com>
>>>
>>>> I don't think they are expected to shrink. Even if the trim gets passed
>>>> to the underlying media I'm not sure if the container's size is also
>>>> expected to shrink.
>>>>
>>>> If you are concerned about space usage, enable ZLE compression and run
>>>> a cron job that zeroes out the free space inside the VMs. Or better, don't
>>>> overbook the space.
>>>>
>>>>
>>>> On Tue, Oct 15, 2013 at 12:22 PM, Ivan Krutskikh <stein.hak at gmail.com>wrote:
>>>>
>>>>> Okay, I've googled up to DisableDeleteNotify parameter. If it equals 0
>>>>> (which it is by default in fact), then TRIM should be up and running. But
>>>>> my zvol devices do not shring with deletion of files from virtual machines
>>>>> disks. How come?
>>>>>
>>>>>
>>>>> 2013/10/15 Tamas Papp <tompos at martos.bme.hu>
>>>>>
>>>>>>
>>>>>> On 10/15/2013 11:20 AM, Ivan Krutskikh wrote:
>>>>>> > http://comments.gmane.org/gmane.os.solaris.opensolaris.zfs/35630
>>>>>> >
>>>>>> > Please, look through the original post
>>>>>> >
>>>>>>
>>>>>> Ohh, thanks.
>>>>>>
>>>>>> tamas
>>>>>>
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