![]() Since no physical IO is involved, we are only dealing with reading data from the memory cache and those basic values should be more or less the same for all types of operations, the only difference is the OS & ZFS overhead involved for the different record sizes and queue depths.įor RND4k Q1T1 the values are 128/4 x 24.55 / 1.8 is ~436 MB/s, which is approx half of all other values. When correcting for the record size the Host OS deals internally for Q32T1 with 128/4 x 53 MB/s is ~1702 MB/s, but in the Host those records are compressed so we are dealing with 1702/1.8 is ~946 MB/s, which is again very close to the values for sequential IO. I expect, it has to do with peak CPU loads, when firing 8 IO operations at once, instead of one at a time.įor the random read operations the throughput looks worse, but to give CDM one uncompressed 4K record, ZFS has to read a compressed 128k record from one of the 2 caches or from the striped HDDs. The 15% difference between Q1T1 at 947 MB/s and Q8T1 at 820 MB/s is difficult to explain. Afterwards reloading Firefox is instantaneous. I see the same effect starting e.g Firefox in a VM, the first time it must be read from L2ARC (SSD cache) or from the striped HDDs, so you notice it. ![]() The Host ZFS system has to find the compressed data in the cache, decompress it and transfer it to the CDM program in Windows 7, there is no physical IO involved. ![]()
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