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Re: [zfs-discuss] Poor ZIL SLC SSD performance

Subject: Re: [zfs-discuss] Poor ZIL SLC SSD performance
From: Bob Friesenhahn
Date: Fri, 19 Feb 2010 12:30:01 -0600 CST
On Fri, 19 Feb 2010, Felix Buenemann wrote:

So it is apparent, that the SSD has really poor random writes.

But I was under the impression, that the ZIL is mostly sequential writes or was I misinformed here?

Maybe the cache syncs bring the device to it's knees?

That's what it seems like. This particular device must actually being obeying the cache sync request rather than just pretending to like many SSDs.

Most SSDs are very good at seeking, and very good at random reads, but most are rather poor at small synchronous writes. The ones which are good at small synchronous writes cost more.

Bob Friesenhahn
[email protected], http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer,    http://www.GraphicsMagick.org/
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