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zfs

ZFS: commands emulation

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I’m considering getting myself an x86 server with Solaris for home use, and today I’ve decided to play around with ZFS on my old Sparc-box.

I believe those of you who are just getting started with ZFS will really like the -n command line option for zfs and zpool, which allows you to see what result would a certain command yield, while there is nothing actually done to your disks.

So, if you’re thinking of creating a new storage pool, you don’t have to actually create it just to see how it will look – you can use -n option instead:

solaris# zpool create -n mypool raidz /export/vdev/d1 /export/vdev/d2 /export/vdev/d3 /export/vdev/d4

ZFS features: RAID-Z

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I started slowly building up my knowledge of ZFS, and have decided to start with the most tasty things. One of them is a RAID-Z approach.

Jeff Bonwick – a ZFS author and one of newly created OpenSolaris ZFS community leaders, wrote a wonderful article on RAID-Z where he thoroughly explains what’s new and cool about RAID-Z compared to RAID-5. Please read this masterpiece here.

Cool things about RAID-Z

  1. A traditional weakness of parity-based RAID schemes – write hole – is fixed
  2. There’s quite a performance improvement because now we have dynamic length stripes – any small amount of data will be treated as a data block of a full-stripe size, and therefore it will be immediately and fully written onto disks.
  3. Data integrity improved – in addition to traditional XORs to validate data based on parity knowledge, each RAID-Z block is validated with a 256-bit checksum.
  4. ZFS has a self-healing functionality built-in. If one of data disks returns corrupted data, ZFS restores the correct data with parity, compares checksums to validate the result, returns this correct data to the disk operation which requested it, and fixes corrupted data on the disk which gave us the corrupted data. Must be really useful!

That’s all for now. Soon there will be new ZFS presentations – and I hope they will have even more information on RAID-Z.

ZFS: filesystem properties

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There is quite a number of ZFS filesystems properties, and I will cover most useful ones today.

I’ll begin with refreshing your knowledge a bit. As I’ve told before, I’m going to create a number of ZFS filesystems on my server for the next few blog entires on ZFS. So, right now I have the following:

solaris# zfs list
NAME                   USED  AVAIL  REFER  MOUNTPOINT
stock                 2.40G  31.1G  8.50K  /stock
stock/oracle          2.32G   693M  2.32G  /stock/oracle
stock/try                8K   512M     8K  /try

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