OpenZFS on illumos » www.prakashsurya.com

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# OpenZFS on illumos

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# Where OpenZFS Originated

- 2001 &ndash; Started at Sun

- 2005 &ndash; Released through OpenSolaris

- 2010 &ndash; illumos spawned; fork of OpenSolaris

- 2013 &ndash; OpenZFS created

- OpenZFS's "home" is in illumos:

- Due to history, but also OS integration: grub, mdd, fma, etc

- But OpenZFS is growing beyond illumos

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# Development model on illumos

- Committer access is granted to "advocates"

- Advocates rely on "reviewers" to verify changes

- E.g. for correctness, good design, etc

- No explicit releases

- All changes must be "release quality"

- Development tools and processes are difficult

- E.g. patch, compile, deploy, test is cumbersome

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# How to facilitate collaboration?

- We encourage "upstreaming" changes

- Difficult with current development model

- How can we make collaboration easier?

- We're open to changes in development model

- Peer code reviews are good

- High overhead to build and test is bad

- Would an OpenZFS repository help?

- If so, what are the requirements?

- How can we get there?

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# Perspective coming from ZFS on Linux

- Large overhead for ZFS on illumos changes

- ZFS on illumos is tightly integrated with illumos

- illumos is the kernel, libraries, and more

- Overhead for "lone" developer is prohibitive

- ZFS on Linux is isolated, little dependencies

- Full illumos build: ~2 hours

- Build ZFS only: ~6 minutes

- ZFS on Linux build time: ~3 minutes

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# ZFS on Linux to illumos (continued)

- Kernel tools are generally much better

- `mdb` is awesome! `crash` probably could be.

- pipelines and walkers

- "SQL for crash dumps"

- dcmds allow extensibility

- ZFS specific extentions

- `::walkers`, `::findleaks`, `::stacks -m zfs`, `::whatis`,
         `::spa`, `::dbufs`, `::blkptr`, `::zio_state`

- No `gdb`; no line number resolution

- `kmdb` and `dtrace` are also very helpful

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# ZFS on Linux to illumos (continued)

- Smaller community of ZFS users on illumos

- People involved are more informed

- Fewer number of people testing

- ZFS test suite available on illumos

- But, no xfstests or filebench

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# `mdb` Example &ndash; `::spa -v`

```
> ::spa -v ! head -n 15
ADDR                 STATE NAME
ffffff096151a000    ACTIVE rpool

ADDR             STATE     AUX          DESCRIPTION
    ffffff095050c780 HEALTHY   -            root
    ffffff09505106c0 HEALTHY   -              /dev/dsk/c2t0d0s0
ffffff09630ac000    ACTIVE tank

ffffff096be74540 HEALTHY   -            root
    ffffff09616f34c0 HEALTHY   -              /dev/dsk/c3t0d0s0
    ffffff09629c9780 HEALTHY   -              /dev/dsk/c3t1d0s0
    ffffff096be6f900 HEALTHY   -              /dev/dsk/c3t2d0s0
    ffffff096be6f280 HEALTHY   -              /dev/dsk/c3t3d0s0
    ffffff096be6ec00 HEALTHY   -              /dev/dsk/c3t4d0s0
    ffffff096be6e580 HEALTHY   -              /dev/dsk/c3t5d0s0
```

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# `mdb` Example &ndash; `::spa -Mh`

```
> ::spa -Mh ! head -n 15
ADDR                 STATE NAME
ffffff096151a000    ACTIVE rpool

ADDR             STATE     AUX          DESCRIPTION
    ffffff095050c780 HEALTHY   -            root
    ffffff09505106c0 HEALTHY   -              /dev/dsk/c2t0d0s0
        ADDR               FRAGMENTATION
        ffffff095986b740              32%
          9:    113 **********
         10:    131 ************
         11:    391 ***********************************
         12:    456 ****************************************
         13:    250 **********************
         14:    227 ********************
         15:    386 **********************************
```

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# `mdb` Example &ndash; `::dbufs`

```
> ::dbufs ! wc -l
182819
> ::dbufs | ::print dmu_buf_impl_t ! head -n 15
{
    db = {
        db_object = 0x76
        db_offset = 0x1a4a0000
        db_size = 0x20000
        db_data = 0xffffff03b2dcd000
    }
    db_objset = 0xffffff0991377c00
    db_dnode_handle = 0xffffff09e0266d58
    db_parent = 0xffffff09e4b22808
    db_hash_next = 0
    db_blkid = 0xd25
    db_blkptr = 0xffffff09e21a5280
    db_level = 0
    db_mtx = {
```

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# `mdb` Example &ndash; `::dbuf`

```
> ::dbufs | ::dbuf ! head -n 15
        addr object lvl blkid holds os
ffffff0af2001010       76 0       d25  0 tank/fish
ffffff0c26001018       84 0       68c  0 tank/fish
ffffff0c260010f8       77 0       1e9  0 tank/fish
ffffff0af20011d0       71 0       dc5  0 tank/fish
ffffff0c260011d8       65 0       b55  0 tank/fish
ffffff0af20012b0       7e 0       fb8  0 tank/fish
ffffff0c260012b8       80 0       a8a  0 tank/fish
ffffff0c26001398       b7 0       a2b  0 tank/fish
ffffff0af2001470       6e 0       91e  0 tank/fish
ffffff0c26001478       86 0       834  0 tank/fish
ffffff0af2001550       85 0       e05  0 tank/fish
ffffff0c26001558       87 0       851  0 tank/fish
ffffff0af2001630       6a 0       353  0 tank/fish
ffffff0c26001638       74 0       49d  0 tank/fish
```

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# `mdb` Example &ndash; `::whatis`

```
> ffffff09e4b22808::whatis ! head -n 15
ffffff09e4b22808 is allocated from dmu_buf_impl_t:
            ADDR          BUFADDR        TIMESTAMP           THREAD
                            CACHE          LASTLOG         CONTENTS
ffffff09e50de9c0 ffffff09e4b22808       3ed28b4787 ffffff09beccc840
                 ffffff095b1c0448 ffffff090f2b6900                0
                 kmem_cache_alloc_debug+0x2e0
                 kmem_cache_alloc+0x2d0
                 dbuf_create+0x5a
                 dbuf_hold_impl+0x177
                 dbuf_findbp+0x17b
                 dbuf_hold_impl+0xf9
                 dbuf_hold_level+0x31
                 dbuf_hold+0x21
                 dmu_buf_hold_array_by_dnode+0x109
                 dmu_read_uio_dnode+0x5a
```

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