Internal HDD has only 27Mb/s write speed

[Earthnail]

I have a MBP Summer 2010, with the original hard drive inside (a 320GB Seagate Momentus HDD). For quite a while now, I noticed that my mac was very slow, starting Word can literally take up to two minutes.

I did a speed test of the HDD with

dd if=/dev/zero of=/tmp/output.img bs=8k count=256k

and get an average write speed of 26,9Mb/s. Actually, I expected this value to be somewhere around 90Mb/s (correct me if that expectation was wrong).

Also, when looking at the system profiler, I found out that the drive was talking SATA1 with my mainboard, although both mainboard and HDD support SATA2.

So here are my guesses:
1. my hard drive starts to fail (although SMART status says it's okay)
2. there's a problem with the HDD<->mainboard connection

Any hints on this?

 

[flatfoot]

Forget Disk Utility's SMART status. Try SMART Utility (google).

I, too, would say it sounds like the HDD is failing.

 

[Earthnail]

SMART Utility also says the drive is fine. I also ran the "short" test in SMART Utility, and it finished without errors. I'm now running the "long" test, will take about 1.5h.

I agree, to me it also sounds like it is failing, but also notice that my MBP is that slow for a few months already, and still, the SMART status seems fine. Thus, it may very well be an issue between HDD and MB. Any further guesses?

 

[pragmatous]

Slow hard drive speeds?

Probably malware or applications doing constant read or writes to the drive in my opinion.

Is the drive light constantly on? You can run any benchmark you want but if the drive is in use you'll get slower ratings.

I would guess software before any kind of hardware issues when it comes to "slowness".

 

[Earthnail]

hmm, I believe a software issue is quite unlikely. looking at the activity monitor, there's very few hard drive access. As I'm writing at this and looking at activity monitor, the highest peak in read/write throughput is 2.9Mb/s, and I highly doubt any sort of "malware" or unknown process could hide from activity monitor.

Edit: As a side note, battery also doesn't stand as long as it used to. Under constant video playback with flash player (which should, by now, be hardware accelerated), it only lasts a little more than 3 hours, which I find is nowhere near the 7 hours it used to last. So that can either mean the battery has aged noticeably in the last two years, or your guess regarding bad software isn't that far off. How could I check the latter case? (No, I'm not going to format and reinstall)

 

[Earthnail]

Today, I removed the cable from the HDD and put it back in, and now I get read and write speeds up to 52Mb/s. Most strangely though, writing seems faster than reading (~40Mb/s), although I have no command line tool for checking read speeds (using Aja System Test here, but Aja's write test fails so I still use dd for checking the write speed).
Any ideas on that?

 

[dusk007]

Well if there is constantly some little random workload (as little as 1MB/s) in the background it can have a big impact on performance.
Maybe check again and see if it goes actually down to zero. I got 0 most of the time and only a couple kB unless I actually do something. 2.9MB/s sounds a lot if there is not any serious workload. An HDD under full random load will only reach 1.5MB/s.

If not it might also be some fragmentation issue. They always say HFS has no problem with that but it still might help to run CCC copy to an external drive and back.

SATA 1 wouldn't be a problem. SATA1 still means 150MB/s which no notebook HDD will ever reach.

 

[Donka]

Today, I removed the cable from the HDD and put it back in, and now I get read and write speeds up to 52Mb/s. Most strangely though, writing seems faster than reading (~40Mb/s), although I have no command line tool for checking read speeds (using Aja System Test here, but Aja's write test fails so I still use dd for checking the write speed).
Any ideas on that?

Nothing strange about write speed being faster than reading - if what you are reading is fragmented then the drive has a lot of work to do to retrieve the full content whereas if you have contiguous free space then writing will just write sequentially to that area without the need to continually move the heads to seek free space.

 

[definitive]

1) Go to About This Mac > More Info > System Report > Serial-ATA and check the Negotiated Speed Link for the hard drive to make sure it's same as Link Speed.

2) Run BlackMagic Disk Speed Test. It might give you a more accurate result.