SSD run faster?

Question

Anyone used SSD on CX4 that shows big difference as far as speed concerns?

I have a 50GB lun from SSD drives and map to AIX server.

Just test to copy 4.7GB on SSD to same lun(SSD).

However the speed came out even slower than regular FC drive !!!

neil_shieh · Answer

read/write cache unchecked.

kelleg · Answer

Is the Read/Write cache on the LUN on or off? Try it in the opposite mode for read/write. glen

neil_shieh · Answer

The latest tests are in the following:

1. Without read/write cache

real 148.25

user 0.66

sys 20.02

2. With read/write cache

real 83.79

user 0.66

sys 20.02

Enable read/write cache ran faster but still slow then regular FC drives.

AJShinn · Answer

Yep, did a bunch of tests awhile back (hey... I like to see my own results and couldnt sleep) and if the workload is sequential no bueno. Not a big shock or anything, like Avi said the cache does a good job of hiding it. Turn the cache off on the FC LUN while doing the test if you want to see how much faster SSD is... its pretty impressive.

Like Avi said, in the small/random department though.... there was no comparison.

We keep a couple "hot" areas of an Oracle database on SSD, and it was a significant boost to the nightly cycle execution time. I had to regroom the EFD's over a weekend once and a lot of people complained while those hot datafiles were on FC again!

Kumar_A · Answer

It would be better if you can simulate some kind of real world application kind of IO. For example, using IOmeter you can try an IO workload directed to the Flash drive LUN.

Generally speaking, you will see the maximum performance benefit (compared to fibre channel drives) when your IO load is:

1) Highly random

2) Has a high Read-to-Write ratio.

3) Small in size.

4) Is highly concurrent (more threads).

These are the characteristics which maximize the usefulness of flash drives.

When you do a host copy operation, you might be doing a highly sequential IO in which case the CLARiiON cache does a very good job masking the difference between FC and flash drives.

JVBowling · Answer

If you are only copying a file(s) then you are doing 100% writes - Not the sweet spot for SSD...

As stated by others, you biggest performance gains will be with small random read workloads...

We have done a lot of testing and that's where we see huge gains - We would not use SSD for large sequential writes.

neil_shieh · Answer

I expect SSD will be running 30 time faster as stated from EMC. However it is not the case so far. Just wondering if any other factors might be holding this ??

kelleg · Answer

Please see the attached - see page 12  - 'Validate the I/O Pattern' and 'Validate the read/write mix'

CLARiiON

SSD run faster?

Was this post helpful?