Help me speed up my SSD in my MBP!

January 5, 2012 10:13 AM

I installed an SSD into my early-2011 13" MacBook Pro. It's working great, but the benchmark tests don't come close to advertised speeds...

I recently purchased an OCZ Agility 3 90GB SSD drive. I then bought OWC's Data Doubler, and once that arrived, got to work.

I have taken out the optical drive. In its place, I installed the Data Doubler with the stock 500GB 5200rpm drive that the computer shipped with.

I installed the SSD where the HDD was, in order to maximize speed (and negate the reported won't-wake-from-sleep issue when drive installed in the optical bay).

Cloned the original hard drive, minus the USERS folder and rebooted. I then turned on TRIM support in Lion according to instructions located online.

Success! Fantastico! Works very well, and it's extremely fast.

However, in benchmarking I'm only seeing 70MB/s read and 140MB/s write (I may have that reversed, but those are roughly the numbers). I believe I should be seeing much closer to 500MB/s??

Is there a step I missed, or is this normal? Should I have enabled something somewhere that I haven't to get the most out of my MBP with SSD?

posted by smitt to Technology (7 answers total)

Which benchmark program are you using, and what kind of benchmark is being run? This is a rather important question, because SSD speeds are dependent on the types of writes and what kind of data is being written to get the 500MB/s speeds. Typically large chunk, compressible, sequential data is that which goes 500MB/s. Small (4K) random incompressible data will not get those speeds. I've used ATTO in the past for SSD benchmarks, and it's a pretty standard one to use.

The other question is whether your SATA port is running at 3Gbps or 6Gbps. I'm fairly certain that the early-2011 MBP's were supposed to have 6Gbps connections for the HDD slot, but I can't find documentation on the specs. If your connection is 3Gbps, then the max throughput would be 300MB/s no matter what. This Anandtech article gives some indication of where to look.
posted by Mister Fabulous at 10:30 AM on January 5, 2012

Response by poster: I used Disk Speed Test by Blackmagic for my benchmarks. I set it using 5GB large files.

SATA should be running at 6Gbps, being in the correct channel according to everything I've seen.
posted by smitt at 10:51 AM on January 5, 2012

A few things to be aware of:

Apparently that SSD compresses data before writing. The 500MB/s speeds people are seeing is with compressible data. With uncompressable data, the speeds are about 1/2.

SSD performance depends, in part, on the number of operations that can be performed in parallel. Within a given generation, larger drives usually have more modules, and can therefore perform more operations in parallel than smaller drives. A 90GB drive is pretty small, and so might have significantly lower peak performance than larger drives.

How full is the SSD? (as I recall, write performance can suffer when the drive is near capacity)

For most tasks on a desktop/notebook computer, the most important drive performance metric isn't MB/s, its IOPS, the number of random reads and writes it can handle in a second. Do those numbers meet expections?
posted by Good Brain at 11:40 AM on January 5, 2012

IOPs on even the lowest SSDs are twice the speed of the fastest HDD, and by now the average is about 100x faster than a standard 7200RPM SATA desktop hard drive. From what I'm seeing around, it's likely that your numbers are reversed, and that it's common for writes to be slower, random or no.
posted by rhizome at 11:58 AM on January 5, 2012

oops, by faster I meant "more IOPS"
posted by rhizome at 11:59 AM on January 5, 2012

Response by poster: The SSD is not very full, 25GB of data is on it right now.

I'm not terribly concerned about the benchmark stats - I mainly want to ensure that I'm getting all I can out of the drive.

So is there anything I can do to optimize, or any settings I should have set, or any programs I should have run on my Mac to get the best performance I can out of the drive?
posted by smitt at 12:17 PM on January 5, 2012

That drive is already overprovisioned (meaning there is actually some reserved space on the drive which is not made available to the user) so filling up the drive shouldn't decrease performance that much. Even running in SATA-II mode you should be getting about 280MB/s read and 260MB/s write. I'm not familiar with the Blackmagic benchmark test, we also use ATTO and indeed the specs do indicate the 500MB/s speeds were measured using ATTO (From the specs listed on newegg )

Note:
1. Maximum Sequential Speeds are determined using ATTO
2. Small file I/O performance is measured using Iometer2008, Queue Depth 32, 4KB Aligned; Logical Block Address (LBA) range: 85%of total drive capacity
3. Small file I/O performance is measured using Iometer2008, Queue Depth 32, 4KB Aligned; Logical Block Address (LBA) range: 8GBIncompressible data performance is measured using AS-SSD; 64 thread for 4K specs
4. Full performance achieved with a native SATA 6Gbps controller

I would guess the Blackmagic benchmark is measuring random read/write or some pre-defined mix of random and sequential read/writes. Try measuring with ATTO to see what performance you get. You should be able to download it free.
posted by TwoWordReview at 5:21 PM on January 5, 2012