On 1/21/07, Liang Yang <multisyncfe991@xxxxxxxxxxx> wrote:
Dan, Thanks for your reply. Still get two questions left. Suppose I have a MD-RAID5 array which consists of 8 disks. 1. Do we need to consider the chunk size of the RAID array when we set the value of Striped_Cache_Size? For example, if the chunk size is changed from 64k to 256k, do we need to adjust the Striped_Cache_Size accordingly?
stripe_cache_size and the chunk size are completely independent settings. The chunk size only determines how much data will be accessed from one disk before proceeding to the next disk.
2. The performance improvement of large size I/O packets (128k, 256k) is larger than small size I/O packets (512B, 1KB) when I change the Striped_Cache_Size. How do you explain the difference here?
With smaller I/Os the chances that you are staying within one stripe are higher so you would see less benefit of having more stripes in the cache.
Liang
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