|
From: | Anthony Liguori |
Subject: | Re: [Qemu-devel] [PATCH 1/4] block: add enable_write_cache flag |
Date: | Mon, 31 Aug 2009 17:53:23 -0500 |
User-agent: | Thunderbird 2.0.0.23 (X11/20090825) |
Christoph Hellwig wrote:
If an unsafe mode is desired (I think it is, for those throwaway testing VMs, or during OS installs), I suggest adding cache=volatile: cache=none O_DIRECT, fdatasync, advertise volatile write cache cache=writethrough O_SYNC, do not advertise cache=writeback fdatasync, advertise volatile write cache cache=volatile nothing (perhaps fdatasync on QEMU blockdev close)Fine withe me, let the flame war begin :)
I think we should pity our poor users and avoid adding yet another obscure option that is likely to be misunderstood.
Can someone do some benchmarking with cache=writeback and fdatasync first and quantify what the real performance impact is?
I think the two reasonable options are 1) make cache=writeback safe, avoid a massive perf decrease in the process 2) keep cache=writeback as a no-guarantees option.
Regards, Anthony Liguori
[Prev in Thread] | Current Thread | [Next in Thread] |