Re: ZFS with Linux: An Open Plea

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On Mon, 16 Apr 2007, Adrian Bunk wrote:

On Mon, Apr 16, 2007 at 04:01:23PM +0200, Tomasz Kłoczko wrote:
...
Few days ago I'm swich two backup servers with few TB storage from Linux to
Solaris .. only because client want use ZFS .. because ZFS is EXCELENT for
this kind tasks (only because it allow save many thousands of
<put_your_currency_name> because it allow better utilize the same storage)
and trust me .. cases like this will be more .. much more and changing
licensing Linux code will be MUCH more easier than reinventing wheel (wich
will be reimplemnting ZFS under GPL).

This is a technical mailing list, so let's start with technical
arguments:

Why did this client want to use ZFS?

Because switching to Solaris was chipper than buying next faster FC/SCSI storage. Simple ?

Because his boss was convinced by a marketing guy that ZFS was the best
invention since sliced bread?

In this scenario ther is no place for "marketing guy" .. try again .. (maybe it can occure in US or Germany but trust me .. not in Poland 8-)

Or due to technical limitations in what Linux currently offers
resulting in ZFS bringing him direct advantages on these servers?

Yes .. it is Linux limitiations because it is very hard to provide simultanouse streams of backup data with threaded compression (using in this case pbzip2) with good CPUs utilization because most streams waits on I/Os and most of CPUs are not fully utilized. All this becase single stram of compressed data can't be easy dinamically switched to another (not busy) disk in JBOD. ZFS by two level allocation (on device and block level) will not wait for finish I/O but will try use another/not busy device in ZFS pool. This is *main* reason integrate in one layer VFS and LVM in case ZFS. By integrate this two layers you can make deciion where data will be written depending on *current* devices utilization. In all other "classic" ways you will break layered OS model .. so in ZFS case conclution like "we must integrate this two layers in one" it is not bug but feacture and was FUNDAMENTAL.

This is not all .. backup data must be safe in best possible form .. in time .. and it mean in this case that checksumming is NECCESSARY. Look .. ext4 for now only have plans for implemting checksuming (http://www.bullopensource.org/ext4/files/ext4.txt) and ATM on Linux there is no FS with this kind abilities .. so yes again: this was Linux technical limitation.

Problem is not on technical area but on licensing and it is plain Linux
word problem because neccessary in this case changes on CDDL side will make
this code less oppended than now .. so you can (probably ?) forget about
GPLing ZFS code (and ZFS it is not all what will good to have from Sol in
Linux).
IMO current Linux licensing less is importand than bringing in possible
simpler way things like ZFS to Linux. So best/simpler way will be start
change Linux licensing for save all GPL goodies and allow interract with
code on license like CDDL.

Licensing is for allow keep in best possible form Linux. If it can't do
this in best possible way it must be change (must evolve .. like many othes
things around).

There are at about 10.000 people who contributed to the Linux kernel,
some of them unreachable or even dead.

Do you know who was Paracelsus ? He was medic hundriet years ago. They discover and verbalise some kind fundamental (?) law for medicine which can be used not only on medicine area. He sayd "kills not subtance but dose of substance". So anything can kill you/animal/project .. you can kill someon also using oxigen (not only low level of oxigen kills but also to much can kill). Try to think on how this law on how many diffret ways can be trasformed/appied to this kind of arguments. Look on how many developers migrate to another unices in last few years (count only two for simplicity like Solaris and MOX). Try looking for public forums statistics for example Linux vs. Solaris and after this try to answer on "is it 10k is it realy big number in this case or not ?" (IIRC google provides very good tools for anyone who want this kind answers).

kloczek
--
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*Ludzie nie mają problemów, tylko sobie sami je stwarzają*
-----------------------------------------------------------
Tomasz Kłoczko, sys adm @zie.pg.gda.pl|*e-mail: [email protected]*

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