Solid-state drives [LWN.net]

Solid-state drives

Posted Aug 2, 2009 0:08 UTC (Sun) by cjb (guest, #40354)
In reply to: Solid-state drives by TRS-80
Parent article: A short history of btrfs

> What's btrfs' SSD story? ZFS gets some amazing performance improvements if you add an SSD for the ZIL or as L2ARC, does the btrfs architecture have any similar parts that could be farmed out to an SSD?

Yes. There are a couple of ideas here -- one (as yet unimplemented) is that you could use the SSD as a caching frontend to larger, slower media behind it. Another is that you could use exclusively the SSD to store metadata items; btrfs doesn't care how far away from data you put its metadata, or even if they end up on the same device.

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Solid-state drives

Posted Aug 2, 2009 1:02 UTC (Sun) by dlang (guest, #313) [Link] (3 responses)

the idea of allowing the metadata to exist on different media is both very interesting and very scary.

on the interesting side, the fact that you can now buy _very_ high speed drives (up to 64G of battery backed ram fast enough that it needs multiple SATA cables to saturate it) means that variations on the space allocation policies can lead to very significant speed-ups.

however, on the scary side, you have the fact that you now need all these different drives to remain operational and available or you run the risk of loosing everything.

a follow-up for after btrfs gets going solidly and reliably would be to look into a multi-drive version that could maintain multiple copies of metadata on different drives

Solid-state drives

Posted Aug 3, 2009 20:31 UTC (Mon) by SEJeff (guest, #51588) [Link] (2 responses)

If you raid drives with btrfs it lets you raid the metadata. Actually, doesn't it do this by default now?

Solid-state drives

Posted Aug 3, 2009 20:41 UTC (Mon) by dlang (guest, #313) [Link] (1 responses)

what I was thinking of is the ability to use different levels of raid for different types of data.
say raid1 for metadata, raid0 for any files in /tmp, raid5/6 for everything else.

Solid-state drives

Posted Aug 3, 2009 21:01 UTC (Mon) by SEJeff (guest, #51588) [Link]

btrfs already supports exactly what you asked:
http://btrfs.wiki.kernel.org/index.php/Using_Btrfs_with_M...

By default data is striped accross multiple disks and metadata is mirrored. You can even mirror metadata on a single disk to prevent bad blocks from corrupting your data. Chris and company did a great job in designing this beast.