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How to understand the physical memory of the directors
Hi!
I am a quite newbie in VMAX and after reading the configuration guide I have some simple questions which address the use of the physical memory in each director. I read that each engine has 2 director and each of them can have 16, 32... GB of physical memory.
1st Question: Is that physical memory the cache? I think yes since I also can read : "The back-end I/O modules are responsible for moving data between physical memory and the disks". Then, if I don't understand incorrectly, the data a host writes is first copied in this physical memory and after a while, it is moved to the disks. is that right?
2nd Quesion: how long does it take to be transferred from the physical memory to the disks? It must depend on something but, on what?
3rd Question: Imagine that I am using FAST (Fully Automated Storage Tiering) and I have different tiers. Is this cache included in these tiers?. For example, if there is a portion of data which is being heavily used, will it be moved to my flash tier or to this physical memory?
Thank you in advance
PedalHarder
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February 22nd, 2012 14:00
Q1. Yes, physical memory is cache. All host writes are written to cache always. Never directly to disk.
Q2. It depends on on the workload of the array.
Q3. Cache by default is global and is shared equally among all Symmetrix devices. FAST moves data between the disk tiers, the cache remains global.Cache can be partitioned, but unless there is a very specific reason to do so, the default global setting is the best.