Kavan2
3 Silver

Symmetrix VMAX performance troubleshooting

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Hi all,

I wanted to ask a general question for Symmetrix VMAX  performance troubleshooting :

1) What to measure generally for performance issues ?

2) Any one has any notes that explains the Metrics used in SPA.

3) If I have a LUN bound to a pool, how can I bind it to another pool without affecting access to it or data loss.

4) Does FAST affects any performance for any Databases etc ????

Any thing you can share on performance issues for VMAX.

Regards,

Kavan

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dynamox
7 Thorium

Re: Symmetrix VMAX performance troubleshooting

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Virtual lun migrator with caviat that you need to move to device with different protection.

Sent from my Verizon Wireless 4GLTE Phone

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Quincy561
4 Beryllium

Re: Symmetrix VMAX performance troubleshooting

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1) Key metrics include FA/DA/Disk Utilization and IOPs.  Also the most important is host response time

2) I thought there were definitions in the help file.

3) VLUN can move a volume from one pool to another without disruption.

4) FAST movements can change the drive speed the data is on, so it can impact the response times.

Kavan2
3 Silver

Re: Symmetrix VMAX performance troubleshooting

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Thanks for your help Quincy56.

I had few questions...

1) for a Meta TDEV when FAST VP is in place, is it better to have striped or concat and why ?? Performance wise which is better considering VP is striping every thing any way.  Does LUN sizes affect the decision ?

2) For a given Disk Group with 160 disks , how can we calculate IOPS of the disk group  available to the applications.??

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Quincy561
4 Beryllium

Re: Symmetrix VMAX performance troubleshooting

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FAST VP really doesn't change the performance for a VP device.  A striped meta will still have higher maximum performance than a non-striped. Size doesn't really matter, but there usually is a relationship with size to IOPs.  More than 8 members is likely to have no or very limited improvements in performance.

Depends on the drive speed.  You can assume the following for planning purposes (with good response times)

150 IOPs per 15k

120 IOPs per 10k

70 IOPs per 7.2k

1000 IOPs per EFD

Remember front-end writes will turn into multiple disk IO depending on the raid protection, 2 for mirrored, 4 for RAID5, and 6 for RAID6.

Kavan2
3 Silver

Re: Symmetrix VMAX performance troubleshooting

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Quincy56,

FAST VP really doesn't change the performance for a VP device.

Above contradicting to what you said earlier as i thought FAST moves between tiers and change perofmance of the device.

My question was a concat thin meta ...every thing is distributed on each disk of the pool in a small 7680 chunks extents ...so for a 2TB  thin lun it will spread on all disk of that group .

Now as this is on all the 160 spindles, it will give the performance , regardless of concat meta or striped meta .

What do you reckon ?

2) Where did you got the IOPs from for the drives ?

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Quincy561
4 Beryllium

Re: Symmetrix VMAX performance troubleshooting

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Ok, what I should have said from a front end point of view.

Obviously the backend performance will change if we move the device to a different drive technology.

Yes, the device is already wide striped, but even 100% cache operations can be significantly different between having one Symm device active on a LUN, vs. having multiple Symm devices active for a LUN.

The IOPs per drive is about what the drives will do for small block reads with 1 IO queued. Simple physics.

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Kavan2
3 Silver

Re: Symmetrix VMAX performance troubleshooting

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quincy,

makes sense now from fast VP side.

For metas...i think we might have to convert ..will it affect the host data access ?

For, IOPs sorry i still don't get it...how can we say all SATA drives with 7200rpm will have 70IOPS..

Sorry not been best with physics ...

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Quincy561
4 Beryllium

Re: Symmetrix VMAX performance troubleshooting

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If you invert the single threaded IOPs, you get the response time.  So 70 IOPs is saying that the drive will get about 14.2ms response times, which is in the range of the expected performance of a SATA drive.

Kavan2
3 Silver

Re: Symmetrix VMAX performance troubleshooting

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Ok, so for a Disk Group with 160 SATA drives it will be times 70 IOPS = 11200 IOPS theoretically.

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Quincy561
4 Beryllium

Re: Symmetrix VMAX performance troubleshooting

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Yes, all reads.

If RAID6 and all writes it would be 1,867 IOPs (divide by six)

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