Contemplating ZFS

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Re: Contemplating ZFS

Post by LaMosca » Sun Dec 16, 2012 11:19 pm

I appreciate the replies and testing info. You make some good points re: SAS in thinking longer term. Hopefully the enclosure(s) will last a long time and that means faster now (even if I don't utilize it right away) would be better. I'll definitely have to think about it more.

It would likely be awhile before I would need to expand if I stuck to my current ideas. I could go up to at least a 10TB volume (5 x 2TB disks) before I would need to think about starting to swap in larger drives. The only thing I think that could cause storage needs like that is 4k video, and since I just went 1080p a year ago, I don't think I'll be looking at 4k within the next 5 years (assuming it even becomes a commercial reality in that period of time). Handbrake works wonders on BluRays, reducing the typical movie down to a file size around 4GB with excellent results.
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pool not expanded as expected

Post by grahamperrin » Mon Dec 17, 2012 7:49 am

gherkins wrote:… even after following the advice to export/import  …


Without understanding the intricacies of how ZEVO is customised for OS X, a long shot: does a restart of the OS work around?
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Re: Contemplating ZFS

Post by ghaskins » Mon Dec 17, 2012 8:43 am

I woke up this morning and realized I was doing "zfs get .." when I was looking for autoexpand, which doesn't make sense. I tried very quickly and saw "zpool get" does in fact have the option, and its off by default. I haven't yet had a chance to test if it works, but my guess is it will. Ill confirm later.
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Re: Contemplating ZFS

Post by TomUnderhill » Wed Dec 19, 2012 1:05 am

ghaskins wrote:Personally, I am using an LSI 9207-8e.

Does the 9207 support booting on a Mac? It's not my first priority, but being able to boot would give me additional options for speeding up my system.
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Re: Contemplating ZFS

Post by ghaskins » Thu Dec 20, 2012 7:42 am

TomUnderhill wrote:
ghaskins wrote:Personally, I am using an LSI 9207-8e.

Does the 9207 support booting on a Mac? It's not my first priority, but being able to boot would give me additional options for speeding up my system.


I'm not sure, I haven't tried it as I have an SSD on the internal SATA bus for that function. I only use the SAS setup for /Users after the OS boots. In some ways I suspect it might, as I know you can see the LSI bios screen come up, but I havent tried it.

-Greg
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Re: Contemplating ZFS

Post by ghaskins » Sun Dec 23, 2012 12:05 am

ghaskins wrote:I woke up this morning and realized I was doing "zfs get .." when I was looking for autoexpand, which doesn't make sense. I tried very quickly and saw "zpool get" does in fact have the option, and its off by default. I haven't yet had a chance to test if it works, but my guess is it will. Ill confirm later.


Good news, I confirmed it works fine. As long as you remember to set "zpool set autoexpand=on", the vdev will expand into the new space. Supposedly there are ways to do it with the online/replace commands too, but I am not sure if the "-e" options documented in solaris are available in Zevo.

-Greg
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Re: Contemplating ZFS

Post by LaMosca » Thu Jan 03, 2013 10:43 am

Great news! Do you have to set autoexpand=on when you initially create the zpool or can you set that any time?
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Re: Contemplating ZFS

Post by ghaskins » Thu Jan 03, 2013 9:08 pm

LaMosca wrote:Great news! Do you have to set autoexpand=on when you initially create the zpool or can you set that any time?


You can set it any time.

-Greg
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Re: Contemplating ZFS

Post by LaMosca » Thu Jan 17, 2013 1:37 pm

More general questions regarding ZFS.

I'm used to LVM on Linux with disks/partitions, volume groups, volumes, and filesystems. I'm trying to figure out what terms in ZEVO/ZFS correspond to LVM resources.

I'm doing some initial configuration and testing with disks now before I do my final setup/configuration.

I purchased two NewerTech MaxPower 6G RAID eSATA cards (arrived, installed) and an external port multiplier enclosure (arriving today) with three sets of five disk slots with corresponding port-multiplier ports. For testing basic ZFS operation and configuration, I connected a single Hitachi 3TB Deskstar drive to a port on one of the new cards. One then has to use NewerTech's browser config tool to configure the disk. I added it to a new JBOD array and only after that would would OS X diskutil see the new disk. I then created a new zpool (called H3) using the zpool command. This created the zpool and was mounted as /Volumes/H3. What exactly does the zpool command do or perhaps a more basic question of what is a zpool?

I was thinking a zpool was equivalent to a volume group in LVM and thus one could carve volumes from this and then create a filesystem on the volume. Is this not the right way to think about it or is the zpool command just doing a number of these steps automatically (with an assumption of one volume in the zpool, followed by creating a zfs filesystem on this volume)?

Thanks in advance for furthering my understanding!

I'm also looking at the man page for zfs to try to further my understanding, but sometimes it takes a simple explanation for me to "get it" initially.
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Terminology and concepts

Post by grahamperrin » Thu Jan 17, 2013 4:00 pm

Someone might like to correct me on some of what follows, but here goes … 

A pool (not a zpool) is created using the zpool command. (Quickstart Guide needs help: Terminology)

It's possible for a pool to comprise a single physical disk, but for redundancy – and for scrub (checkup) to effectively repair errors – it's more common to find two or more disks in a pool.

Every pool has at least one file system. The file system at the root of the pool has the same name as the pool.

Mount a file system, it appears as a volume.

Think less of carving (fixed sizes); think more of the fluid nature of a pool.

With two or more file systems in a pool, and with the default of no quotas, free space is calculated at the pool level. You need not define the size of a file system.
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