Monday Dec 14, 2009

Make The Most Of Your SSD With ZFS

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Rationale

 If you're anything like me, you're lucky if you have a single SSD in your workstation or server. I had a dilemma in the past, I couldn't quite find a way to make the most of my one flash drive: I had to chose between making it a ZIL or use it as L2ARC. I dreaded having to make a definitive choice for one or the other. When I installed my workstation with OpenSolaris 2009.06, I had an idea in mind, so I installed the system on the SSD in a small partition (10GB) and left the rest of the drive unallocated if you catch my drift...

Bird's Eye View

Simple! Just partition the SSD to be able to use it as both L2ARC and ZIL in whatever proportions you think is going to suit  your needs. Note however that the IOs are shared between your partitions on the same drive. From my testing though, I can tell you that with this setupu you're still coming out on top in most situations.

The Meat

It's all pretty simple really, when you install solaris, you have a choice of installing on "whole disk" or to use the tool to make a smaller custom partition. I cut out a 36GB partition which allows ample room for the system and swap. The rest of my 64GB SSD is left unallocated at install time, we'll take care of everything later.

The second disk in my system is a 300GB 10,000 rpm SATA drive which, being fast but small, I wanted to leave whole for my data pool (keep in mind that the rpool is a little different than your regular pool, so make sure to treat it accordingly). That is why I decided to compromise and use some of the SSD space for the system. You don't have, you could partition your spindle and have the system on there.

Now, that you have opensolaris up and running, install GParted to be able to edit your disks partitions. You can either use the opensolaris package manager or

pfexec pkg install SUNWGParted

It's all downhill from here. Open GParted. If you just installed it, you will need to log out and back in to see in the GNnome menu. It will be in Applications->System tools->GParted Partition Editor

Select your flash drive and carve out a 2GB partition for your ZIL and assign the remaining space for L2ARC. Apply the changes and keep the window open.


Note the two devices path in /dev/dsk because that's what we'll use to add these two SSD partitions as performance enhancing tools in our existing pool.

arnaud@ioexception:/data/dsee7.0/instances$ pfexec zpool add data log /dev/dsk/c9d0p2 cache /dev/dsk/c9d0p3

Let's check how our pool looks now...

arnaud@ioexception:/data/dsee7.0/instances$ zpool status data
  pool: data
 state: ONLINE
 scrub: none requested
config:

    NAME        STATE     READ WRITE CKSUM
    data        ONLINE       0     0     0
      c8d0      ONLINE       0     0     0
    logs
      c9d0p2    ONLINE       0     0     0
    cache
      c9d0p3    ONLINE       0     0     0

errors: No known data errors

Et voila!

You've got the best of both worlds, making the absolute most of whatever little hardware you had at your disposal!

Enjoy!

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