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Tuesday Nov 06, 2007

Testing MacOS X read only ZFS capability

When I first heard Jonathon Schwartz announce that MacOS 10.5 (aka Leopard) would include ZFS, I was psyched! As a Microsoft free user of Macs and Unix since the late 1980s, I was looking forward to seeing Sun's open source file system in MacOS and was convinced that its snapshot capability would be the basis of Time Machine, Apple's new backup facility. Imagine my disappointment when news trickled out that the first release of Leopard would only included a basic, read-only implementation of ZFS. What good is a read only file system?

Leopard shipped two weeks ago and ZFS is almost impossible to find by anyone but developers and OS nuts like me. It's completely invisible to the typical Mac user. Then I heard a different piece of news. Apple shipped 2 MILLION copies of Leopard in the first weekend! Once ZFS becomes a more prominent part of MacOS, they will be able to touch many more people than Sun ever could in our enterprise ready Solaris OS. I feel confident that Apple will continue to innovate on top of ZFS. And in typical Apple style, the end user (like my 82 year old mother who loves her Mac and has no idea that she's running Unix) may never know what ZFS is, but they will appreciate the benefits that they get. The same will no doubt be true in their implementation of Sun's Dtrace technology.

With that in mind, I set about to find a way to prove to myself that ZFS is in there and compatible with ZFS in Solaris 10. Here's what I did using my MacBook Pro, VMware Fusion 1.1RC1 beta and Solaris 10 08/07.

Halt Solaris and shut down the VM
VM > Settings > + > Add USB controller
Boot Solaris
Plug in the USB memory stick. (the VM must have focus)

This was actually the most time consuming part of the whole exercise. It did not mount reliably)

If you're lucky, mount shows: /rmdisk/noname on /vol/dev/dsk/c2t0d0/noname:c
umount /rmdisk/noname
zpool create usbpool /vol/dsk/noname
zpool list
NAME SIZE USED AVAIL CAP HEALTH ALTROOT
usbpool 120M 88K 120M 0% ONLINE -
zfs list
NAME USED AVAIL REFER MOUNTPOINT
usbpool 85K 87.9M 24.5K /usbpool
zpool export usbpool
Suspend the VM and quit Fusion to avoid confusion
Re-insert the USB stick.
Finder complains that the disk is not readable. Click Ignore
Open a terminal on the Mac.
sudo bash
zpool import
pool: usbpool
    id: 13927799406997242219
state: ONLINE
status: The pool is formatted using an older on-disk version.
action: The pool can be imported using its name or numeric identifier, though
    some features will not be available without an explicit 'zpool upgrade'.
config:

    usbpool     ONLINE
    disk2     ONLINE
zpool import usbpool
Mount shows:

usbpool on /Volumes/usbpool (zfs, local, read-only)

I was then able to view and copy files from the newly mounted pool
Woooo Hoooo!

Why should you care?

ZFS is a truly easy to use, open source, endian independent, scalable, reliable file system. This is the first example of it being ported to a commercial, consumer oriented product.

Things to like about ZFS:

Open source
Multi-platform (Solaris, MacOS, BSD unix, Sparc, X86, PowerPC)
Freely included in Solaris 10 (download now)
Easy to use
Built in data integrity
Linux Torvalds likes it.
Scalable 128 bit file system

Learn more at the ZFS learning center.

Posted at 09:23PM Nov 06, 2007 by jimlaurent in Solaris tips | Comments[15] | Permalink

Comments:

Apple has the beta of a read/write ZFS driver and tools on her developers website.
You will need to sign up for a (free) developers account to get it though.

Posted by gmlk on November 07, 2007 at 04:40 AM EST #

Now try it accross three OSes, Solaris, OS-X and BSD !-)

Posted by Sean on November 08, 2007 at 04:54 AM EST #

One thing I am interested to try is having a native disk used by zfs using solaris in parallels (via bootcamp integration) with read-write access via nfs and read-only access native.

Bit of a kludge, I admit, but I'm really eager for ZFS's data protection features for my files.

Posted by Byron Servies on November 08, 2007 at 12:09 PM EST #

My experience with R/W ZFS on Leopard (10.5.1 / Powerbook)...

Also posted to: zfs-discuss@opensolaris.org...where I received 1 very thoughtful response. This below text modified from the original post to reflect some of the answers received.

Also, dtrace's GUI now appears in the developer tools as "Containers" as oppsed to "xRay", and it has a Garageband-like interface.

Also: http://www.mactech.com/articles/mactech/Vol.23/23.11/ExploringLeopardwithDTrace/index.html

And:
http://www.dtracescripts.com/

...May be of interest to the dtrace/Containers/Leopard set.

I am playing around with the latest Read-Write ZFS on Leopard and am confused about why the available size of my admittedly tiny test pool (100 MB) is showing at ~2/3 (63 MB) of the expected capacity. I used mkfile to create test "disks". Is this due to normal ZFS overhead? If
so, how can I list / view / examine these properties? I don't think it's compression related (BTW, is compression ON or OFF by default in OS X's current implementation of ZFS?).

tcpb:jpool avatar$ uname -a
Darwin tcpb.local 9.1.0 Darwin Kernel Version 9.1.0: Wed Oct 31 17:48:21 PDT 2007; root:xnu 1228.0.2~1/RELEASE_PPC Power Macintosh

tcpb:jpool avatar$ sw_vers
ProductName: Mac OS X
ProductVersion: 10.5.1
BuildVersion: 9B18

tcpb:aguas avatar$ kextstat | grep zfs
125 0 0x3203a000 0xcf000 0xce000 com.apple.filesystems.zfs (6.0) <7 6 5 2>

I created a test pool in the "aguas" directory on an external firewire HDD:

cd to my zfs test directory: "aguas" on an external HDD..
cd /Volumes/jDrive/aguas/

Create 5 100MB files to act as "Disks" in my Pool...
sudo mkfile 100M disk1
sudo mkfile 100M disk2
sudo mkfile 100M disk3
sudo mkfile 100M disk4
sudo mkfile 100M disk5

Create MIRROR'd Pool, "jpool" using 1st two Disks...
sudo zpool create jpool mirror /Volumes/jDrive/aguas/disk1 /Volumes/ jDrive/aguas/disk2

zpool list =====>
NAME SIZE USED AVAIL CAP HEALTH
ALTROOT
jpool 95.5M 151K 95.4M 0% ONLINE
-

zpool status =====>
pool: jpool
state: ONLINE
scrub: none requested
config:

NAME STATE READ WRITE CKSUM
jpool ONLINE 0 0 0
mirror ONLINE 0 0 0
/Volumes/jDrive/aguas/disk1 ONLINE 0 0 0
/Volumes/jDrive/aguas/disk2 ONLINE 0 0 0

errors: No known data errors
=====

Added a spare:
sudo zpool add jpool spare /Volumes/jDrive/aguas/disk5

zpool status =====>
pool: jpool
state: ONLINE
scrub: none requested
config:

NAME STATE READ WRITE CKSUM
jpool ONLINE 0 0 0
mirror ONLINE 0 0 0
/Volumes/jDrive/aguas/disk1 ONLINE 0 0 0
/Volumes/jDrive/aguas/disk2 ONLINE 0 0 0
spares
/Volumes/jDrive/aguas/disk5 AVAIL

errors: No known data errors
=====

"jpool" NOW SHOWS UP ON THE FINDER...

tcpb:aguas avatar$ df -h
Filesystem Size Used Avail Capacity Mounted on
/dev/disk0s3 112Gi 103Gi 8.7Gi 93% /
devfs 114Ki 114Ki 0Bi 100% /dev
fdesc 1.0Ki 1.0Ki 0Bi 100% /dev
map -hosts 0Bi 0Bi 0Bi 100% /net
map auto_home 0Bi 0Bi 0Bi 100% /home
/dev/disk1s14 56Gi 50Gi 5.4Gi 91% /Volumes/jDrive ONE
/dev/disk1s10 75Gi 68Gi 7.3Gi 91% /Volumes/jDrive
/dev/disk1s12 55Gi 52Gi 2.5Gi 96% /Volumes/Free 55
jpool 63Mi 59Ki 63Mi 1% /Volumes/jpool
=====

OK, GIVEN:
zpool list =====>
NAME SIZE USED AVAIL CAP HEALTH
ALTROOT
jpool 95.5M 151K 95.4M 0% ONLINE
-

*WHY* ONLY 63MB?!?:
jpool 63Mi 59Ki 63Mi 1% /Volumes/jpool

More info (I turned COMPRESSION on after I noticed the
discrepancy.) ...

tcpb:jpool avatar$ sudo zfs get all jpool =====>
NAME PROPERTY VALUE SOURCE
jpool type filesystem -
jpool creation Tue Nov 20 14:48 2007 -
jpool used 392K -
jpool available 63.1M -
jpool referenced 59K -
jpool compressratio 1.00x -
jpool mounted yes -
jpool quota none default
jpool reservation none default
jpool recordsize 128K default
jpool mountpoint /Volumes/jpool default
jpool sharenfs off default
jpool checksum on default
jpool compression on local
jpool atime on default
jpool devices on default
jpool exec on default
jpool setuid on default
jpool readonly off default
jpool zoned off default
jpool snapdir hidden default
jpool aclmode groupmask default
jpool aclinherit secure default
jpool canmount on default
jpool shareiscsi off default
jpool xattr on default
jpool copies 1 default
=====

So, zpool list =
NAME SIZE USED AVAIL CAP HEALTH
ALTROOT
jpool 95.5M 479K 95.0M 0% ONLINE -

While zfs list =
NAME USED AVAIL REFER MOUNTPOINT
jpool 392K 63.1M 59K /Volumes/jpool

-and-

tcpb:aguas avatar$ df -h
jpool 63Mi 59Ki 63Mi 1% /Volumes/jpool

OK, so the pool (as referenced by zpool) shows the expected SIZE but the filesystem part (as reference by zfs and df) shows ~2/3 the expected SIZE.

Hmmm...this leads to something about ZFS that I was confused about: I thought that I had to use the zfs command to create a filesystem on my pool before it was useable. I was surprised when "jpool" popped up on
my Desktop as a removable drive as soon as I created it with zpool. Is there a default filesystem created automatically when the pool is created? If so, does it cover the whole pool?

Again, the pool = 100MB but the fs = 64MB.

Maybe this is just fs overhead (if so, what/when/how to examine?) and maybe my pool is too small. If the test pool was a more reasonable 10GB and the 40MB is normal fs overhead than we are talking 0.4% as opposed to 33%(40MB) on a test pool of 100MB. If my test pool was
10GB, then I probably wouldn't even have noticed.

OK! Thanks for reading this if you got all the way down here!

SUMMARY:
1) Why the difference between pool size and fs capacity?
2) If this is normal overhead, then how to you examine these aspects of the fs (commands to use, background links to read, etc. (If you say RTFM then please supply a page number for "817-2271.pdf"))?
3) What's the relationship between pools (zpool) and filesystems (zfs command)? / Is there a default fs created hwne the pool is created?
4) BONUS QUESTION #2: How does a frustrated yet extremely seasoned Mac/OS X technician with a terrific Solaris background find happiness by landing a job at his other favorite company, Sun? (My "friend" wants to know.)

Thanks!

-Anonymous Mac Tech

Posted by Jason Jones-Jones on November 27, 2007 at 12:33 AM EST #

Thanks for posting this detailed review. As I recall, the "overhead" that you are asking about is a minimum required for the ZFS data structures. In other words, if you were to create a 200 MB zpool, there would not be 128 MB of usable space but more like 175 MB.

The zpool man page can be found at: http://docs.sun.com/app/docs/doc/816-5166/zpool-1m?a=view

zpool create automatically mounts the pool although you can specify an alternate mount point with the -m option.

Looking for Jobs at Sun?

http://www.sun.com/corp_emp/

Posted by Jim Laurent on November 27, 2007 at 09:15 AM EST #

CORRECTION: Apple's dtrace GUI was incorrectly referred to as "Containers" in a previous post (which is of course not Apple's but Sun's [virtualization?] tool).

The CORRECT name is Instruments:

"When you need help debugging, Xcode 3.0 offers an extraordinary new program: Instruments. Taking interface cues from timeline editors such as GarageBand, Instruments lets you visualize application performance like never before."

http://www.apple.com/macosx/developertools/instruments.html

http://developer.apple.com/documentation/DeveloperTools/Conceptual/InstrumentsUserGuide/

Sorry for the mix-up.

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Author: James Laurent

Jim Laurent's Weblog

Tuesday Nov 06, 2007

Testing MacOS X read only ZFS capability

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