2
My SSD specifications say its peak read/write is 550/500 MB/s. What influences the actual speed? Is there any way to make a file that I need to be read fast to be always read at max speed?
2
My SSD specifications say its peak read/write is 550/500 MB/s. What influences the actual speed? Is there any way to make a file that I need to be read fast to be always read at max speed?
6
SSDs are typically compared using four speed measurements:
The sequential speeds are usually higher than random speeds, because these are sustained reads or writes that can fully benefit from the fact that SSDs have several flash memory chips that can be accessed in parallel. Random reads and writes might only access one flash chip.
In your case, the manufacturer will be quoting optimal sequential speeds: using a large file, with no other operations at the same time.
Two points should be noted:
3
You should not have to worry about anything on the drive side. On the OS side however, if you are separately reading other files, that could eat part of your 550 MB/s away.
As an aside, as this is something that you typically cannot change, your file will be read/written faster if they are compressable. Credit to @Col.
3Also some SSD's will only write at maximum speed for compressible files, I think it's the one's that use the Sandforce controllers – Col – 2011-08-17T16:04:06.243
He is talking about reading. – soandos – 2011-08-17T16:04:41.937
I just checked and it affects read speed as well, I wasn't sure about that. – Col – 2011-08-17T16:10:10.447
@Col, mine uses sandforce, but with fast cpu speeds also hdd can read/write faster through gzip pipes and things like that. What about max entropy (uncompressible) data read/write? – Dani – 2011-08-17T16:32:23.337
@Dani The compression all takes place on the drive rather than using CPU I think but I'm not sure how badly totally noncompressible files will affect performance. – Col – 2011-08-17T16:42:02.267
@Col: if its using compression, will I get more space than the SSD advertises? – Dani – 2011-08-17T16:44:31.147
@Dani I think if anything the opposite tends to be the case but I'm not an expert, you'd be better off finding a review of your specific SSD on somewhere like bit-tech.net or tomshardware. – Col – 2011-08-17T16:51:22.033
0
All files on an SSD will always be readable at maximum speed. You can't prioritise or de-prioritise any data on an SSD, all of it is equal.
I'm using SATA 6.0 Gbps. if you say sequential is faster, will defragmenting the drive frequently offer a large performance boost? as for my day-to-day performance, its mostly games and video converting. – Dani – 2011-08-17T16:36:17.027
3@Dani Do not defragment an SSD - this will cause unnecessary wear of the flash memory, and will probably reduce performance over time. – sblair – 2011-08-17T16:40:43.040
that new to me. I can understand the wear part, but why would it reduce performance? – Dani – 2011-08-17T16:42:43.990
@Dani As the result of wear. Blocks that are "worn" will eventually be removed from the pool of usable space. Generally, the bigger the pool, the faster the SSD. Also, if TRIM is not enabled, there will be a much more immediate drop in write performance. – sblair – 2011-08-18T11:04:01.343
I don't know if trim is enabled. I have it connected to Z68 chipset SATA 6 Gbps controller with ACHI enabled. does that mean TRIM is on or I have to dig further in the BIOS? Also I have Marvell PCIe based SATA 6 Gbps controller, is there any chance moving the SSD on it will increase performance/lifetime? – Dani – 2011-08-18T13:50:42.680
@Dani For Windows 7, it should be enabled, and it's easy to check this. It should also be supported on ext4. For OS X, it needs to be an Apple-approved drive. If not supported by the OS, some manufacturers have software that "manually" TRIMs the drive, such as the Intel SSD Toolbox.
– sblair – 2011-08-18T14:04:54.903