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From: | Paolo Bonzini |
Subject: | Re: [Qemu-devel] [PATCHv2 RESEND] block/iscsi: speed up read for unallocated sectors |
Date: | Mon, 28 Apr 2014 16:39:35 +0200 |
User-agent: | Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.4.0 |
Il 28/04/2014 15:43, Peter Lieven ha scritto:
b) the allocationmap should be allocated even for out-of-range opt_unmap_gran, using a granularity of 64 sectors in that case.Would the increase of the resolution bring any benefit? If we increase the resolution I think all sectors falling into the same physical cluster would end up with the same status.
What if opt_unmap_gran is 32K or lower? In this case you're not using an allocationmap.
c) an opt_unmap_gran of 32K should be used by QEMU as a cluster sizeDo we have evidence of used cluster sizes on real hardware? I only know our Equallogic storages which have 30720 sectors.
IDE does not specify the granularity, so an IDE disk will show a granularity of 1 sector (but it has LBPRZ=0).
d) the threshold should be dynamic and equal to iscsilun->cluster_sectorsI don't think this is useful. For big cluster_sizes we will end up to never use the allocation cache.
Right. Paolo
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