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RecoverPoint replica LUNs hardware requirements
Hi All,
Is there a requirement for the RecoverPoint replica LUNs: should all be SAS only, NLSAS only, or both? What guidelines can I use to determine which drive types will be better suited for RecoverPoint replica LUNs? Are there going to be RecoverPoint performance issues if the replica LUNs are on NLSAS pool? Does EMC have any docs for that?
All input is appreciated.
forshr
1.1K Posts
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October 14th, 2014 14:00
Hi there,
Ideally you want to use the same type of drive for the replica volumes as you would for the drives underpinning the source volumes. However, if this is not possible and the choice is a slower drive then the probablity is that you will need more of them purely from a performance perspective.
When we size for RecoverPoint one of the areas we focus on is the journal and replica performance as part of the distribution process. For every write I/O the journal incurs three I/O's (W, R, W) and the replica (R, W). Therefore, performance can be an issue at the replica if the are not sufficient drives to underwrite the performance although volumes/LUNs striped across a storage pool offset this as there is often more drives in the pool than the performance requirement for the distribution to the replica volumes.
Regards,
Rich
victory_is_mine
236 Posts
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October 15th, 2014 11:00
Thank you Rich.
When you are saying 'you will need more of them purely from a performance perspective', you mean that the total raw IOPs of the drives underpinning the replica volumes should be equal to the raw IOPs of the source drives. So let's say if I have 20x15K SAS drives on the source, which would give me roughly - 20x180=3600IOPs, and if my only choice for the replica is NLSAS drives I should have 40 7.2K NLSAS drives - 40x80=3600IOPs. However it will not guarantee me the performance of the 15K SAS drives.
brettesinclair
715 Posts
1
October 22nd, 2014 05:00
You're right, although a pool of NL-SAS can be built to have similar IOPs as a SAS based pool, the performance characteristics are going to be different.
NL-SAS has far greater seek and access times, and you'll also be inclined to run it RAID 6 so you'll be contending with an increased write penalty.
Personally, I've never used NL-SAS for replicas, only SAS, albeit often 10k and larger capacity (as opposed to 15k for source) with the understanding that on the rare case I need to actually use them, there'll be some degree of performance penalty.