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List:       freebsd-hackers
Subject:    Re: Is mdconfig in FreeBSD and zRAM in linux are same?
From:       Allan Jude <allanjude () freebsd ! org>
Date:       2017-06-05 14:14:35
Message-ID: 18f2c9ee-9a7e-d4e4-8e37-1c8d0b2e1e3e () freebsd ! org
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On 2017-06-05 02:45, Prateek Dilip Halwe wrote:
> Hi FreeBSD Hackers,
> 
> Hope you all are doing good.
> 
> *Introduction:*
> I was looking to experiment with my machine by improving its performance by
> fastening or minimizing the page swapping from the disk.
> 
> I came across something called as zRAM <https://en.wikipedia.org/wiki/Zram>
> in Linux, I searched the same for FreeBSD, I came across mdconfig. For more
> details on zRAM a good link is here
> <https://www.kernel.org/doc/Documentation/blockdev/zram.txt>.
> 
> *Question:*
> My question is, are zRAM and mdconfig doing the same job? Has anyone done
> some experiments with zRam on FreeBSD, in my case Is it meaningful to
> consider zram for FreeBSD, given that something like mdconfig is already
> available in FreeBSD? If so, please share some details and result.
> 
> Thanks in advance!
> 
> Thanks & Regards,
> Prateek Halwe
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> 

mdconfig creates a memory disk, but it does not perform any compression,
so it is not really like zram.

With FreeBSD 11.1 and newer, ZFS supports 'compressed ARC', so zvol's
you create have their pages cached in ram compressed, but are still
backed by disk as well. This is not really the same thing because it
provides durability and safety that zram does not.


-- 
Allan Jude
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