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my247

10.000 RPM VS 128MB Cache VS Hybrid SSD Performance

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We are planning to create virtualization like VPS Hosting on the server for our client in the office but the questions that has been lingering around is that the hard drive and please give me some advise if possible

we are looking into 3 drives

Seagate Constellation ES.3 ST1000NM0033 1TB 7200 RPM 128MB Cache

VS

Western Digital WD VelociRaptor WD1000DHTZ 1TB 10000 RPM 64MB Cache

VS

Seagate Hybrid Drives ST1000LM014 1TB MLC/8GB 64MB Cache - HYBRID SSD

QUESTIONS IS (please answer it in order if possible, i would really appreciate it)

ASSUMING we do not use it in RAID environment just single drive

1) Which drive will perform better if we do Virtualization (which we are using KVM Virtualization on Linux server)

2) Since each drive have different role, one has higher RPM and one have higher cache and one have lower RPM (hybrid ssd but it has SSD 8GB on it) - which one will reduce I/O on the server/

3) if we used raid controller, is that right the cache on the drive itself will be disable and therefore the raid controller cache will come into the play - what i mean is, if the raid controller have 128MB cache and the bare drive have only 64MB Cache, as soon as we use raid controller that have 128MB cache, the cache for the drive will be 128MB CACHE?

4) Which drive from those 3 will be the best for read, write and reduce I/O under extreme condition

PS: I dont put SSD into the picture because of the pricing, therefore i need to know how can we create similar to SSD performance using above drives?

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1. Depending on the size of the hot data in your environment, if you spill outside of the 8GB of cache on the Seagate Hybrid drive, your order in terms of performance will be Velociraptor > Constellation ES.3 > Seagate Hybrid. I'm not sure how many VMs will be living on each drive, but that will be the deciding factor.

2. This points back to the first question of how large the VMs are that will be sitting on the drive. I'm not sure I understand the part about reducing the I/O though... since if the VMs live on that drive the I/O would be how fast that drive is unless you are using this drive as cache for a larger storage pool.

3. All RAID cards allow drive cache and RAID cache to work together. In most setups I believe the default is to keep it on.

4. All points back to VM size, but at least the write I/O question is easy. The Velociraptor will win that hands down, since the Hybrid drive is read-only cache. That notebook hard drive will be painfully slow if your VMs spill outside of the cache.

You don't really mention this, but what is the overall budget (or is there one at all?). Your selection of drives is pretty strange for an enterprise or office virtualized environment, especially that mobile Seagate Hybrid model. Are you re-purposing drives from another project?

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It sounds like you expect to need 1 TB of storage. But since you brought up the Seagate Hybrid drive it seems like your hot data pool would be rather small. If this is true you might be best served by an affordable SSD (128 - 256 GB) for the OS's (maybe with data deduplication?) and some HDD for storing the cold data.

If your hot data is more like 1 TB in size don't punish yourself with anything less than the raptor. But in this case even this fine drive could be overwhelmed - depending on the actual load this system is going to face.

MrS

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I'm not sure any single drive in this situation will work out well, HDD or SSD since it can't handle a single drive failure.

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