ZFS is an open source file system and volume manager that provides features like unlimited capacity, data integrity checking, snapshots and clones. The presentation discusses N+1 ways to better use ZFS including designing storage pools with redundancy, testing pool performance, tuning the filesystem, and maintaining the system through scrubs and resilvering. Reasons for using ZFS in DevOps environments are also provided, such as performance, scalability, replication abilities, and using snapshots for deployments and backups.

1. ZFS on the server and the
desktop
N+1 ways to better store your data
Presented at NLUUG
21-11-2013

2. About
Matthias van der Heide
Storage Network Engineer
Inprove IT BV
an EraStor member
@matthiasvdh on Twitter

3. Contents
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ZFS Intro
Features
N+1 ways
Why use it in DevOps
Where to get it

4. What is ZFS?
• “Zettabyte File System”
• Sun, now Oracle
• Thank Sun for OpenSolaris and releasing ZFS

5. ZFS Features
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Yes, it is a file system
It is also volume manager
Virtually unlimited capacity
Transactional
Multiple types of redundancy
Virtually unlimited snapshots, clones
Smart caching
Versioned on-disk format

6. Copy-on-write

7. Checksums
NL 08 IN GB 00 00 00 05 55

8. ARC
• Adaptive Replacement Cache
• Combines MRU and MFU
• Uses ghost lists
• Consumes (a lot of) memory, extend to SSD

9. ZIL
• ZFS Intent Log
• In memory
• On the pool
• Optionally on a seperate log device (SSD)

10. Transaction Groups (TXG)
Open
Quiescing
Syncing
• Accept new writes
• Wait for I/O to complete
• Write the data to disk

11. N+1 ways
• Designing your pool
• Testing your pool
• Tuning the filesystem
• Maintenance

12. N=1: Designing your pool
• Your performance and redundancy needs
determine your pool design
• You can change it, only slightly, afterwards
• Consider a system with 4 HDDs
• Now what do I do?

13. Redundancy types
• A vdev is the building block of the zpool
• Everything is striped over vdevs
• Options:
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Leaf (1)
Mirror (2..n)
RAID-Z1 (n+1)
RAID-Z2 (n+2)

14. Options
• Stripe over all drives
• Stripe over mirrors
• RAID-Z1
• RAID-Z2

15. Fun options
• Dual RAID-Z1
• 4-way mirror
• HDD as slog device

16. N=2: Testing your pool
• Simple: time dd
• Iometer
• Vdbench
• FIO

17. N=3: Tuning your filesystem
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Block size
Log bias
Access time
Sync on/off
Caching on/off

18. N=4: Maintenance
• ZFS will tell you when stuff is broken
• Check data on all reads
• Regular scrubs

19. Scrubs
• Scans the pool for data integrity
• Checks checksums
• Restores data if needed
• Can take a while on large pools

20. Scrub

21. Scrub time
Estimate accuracy
100,00
90,00
80,00
70,00
60,00
50,00
40,00
30,00
20,00
10,00
0,00
1
3
5
7
9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53 55 57 59 61 63 65 67 69 71
Estimate accuracy

22. Resilvers
• When replacing a device
• When adding a device back after removal

23. Simple detach/attach

24. After being offline

25. New device

26. Future work on ZFS
• Feature flags enables development of features
seperately
• Persistent L2ARC
• Larger block support
• Dedupe tables on SSD

27. Why use it in DevOps
• ZFS performs
• ZFS scales
– From your laptop to your workstation to your cloud
• ZFS replicates
– Using zfs send/receive you can deploy copies of your
VMs to other hosts
– Keep simple backups of your repos and machines
• Use snapshots to boot into new versions of your
operating system

28. Where to get it?
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FreeBSD
Mac
ZFS on Linux
Illumos (EraStor OS)
NexentaStor (based on OpenSolaris/Illumos)
OpenZFS - http://open-zfs.org

29. Links
• Open ZFS Project
http://open-zfs.org
• ARC Paper
http://citeseer.ist.psu.edu/viewdoc/summary?doi=10.1.1.1
3.5210
• NOSIG
http://www.nosig.nl/
• Erastor
http://www.erastor.eu