HDD cache question?

[toreses]

I wonder how much faster for a 32m cache hdd compare to a 16m cache hdd.
is the difference huge? or just very tiny?

 

[AnnonUSA]

Tiny

 

[Ratman6161]

Originally posted by: toreses
I wonder how much faster for a 32m cache hdd compare to a 16m cache hdd.
is the difference huge? or just very tiny?

The best answer is that how well caches work depends on what you are doing and whether your application and activity benefits from it. But agree for the vast majority it won't make any difference.

 

[Starrx05]

Yep.... when the 8MB came out vs. the 2M cache for HDs, it made some difference because back then people were switching from Win 98 to 2000 and XP with NTFS which allows large files over 4GB. Also back then, SATA drives weren't available. Nowadays, HDs are so fast so the cache plays less roles. It still help somewhat if you reading/writing large files in sequential manners.

 

[sutahz]

Marketing. Not a total waste but not a noticeable boost to performance.

 

[degibson]

The disk-side cache is almost irrelevant these days because OS-side caches are much larger and much faster. Typically, the OS will use uncommitted RAM as a file system cache, and uncommitted RAM can be quite large (I have 1.83 GB uncommitted right now).

As an aside: Disk latency isn't much faster than it was in the 2M cache days -- what has changed is the bandwidth (IDE->SATA, for instance), which is orthogonal to the cache.

 

[MerlinRML]

Originally posted by: degibson
The disk-side cache is almost irrelevant these days because OS-side caches are much larger and much faster. Typically, the OS will use uncommitted RAM as a file system cache, and uncommitted RAM can be quite large (I have 1.83 GB uncommitted right now).

Disk cache is very relevent. Try turning off your disk cache and see how slow your system feels.

In terms of 16MB vs 32MB, the performance difference is slight. It's probably nothing you would notice without doing some intense disk I/O or benchmarking.

 

[Rubycon]

You cannot turn off the disk cache on the drive itself without a special program to do so. SCSI disks often use multisegmented caches which are programmable but that's getting off a bit...

What's more important than size is the actual tuning of the firmware to use the cache effectively. Larger caches can improve random writes and system responsiveness at the highest queue depth. Of course the biggest pitfall of having very aggressive write back policies in place is the risk of corruption/data loss is high in the event of power loss or sudden halting of the system. Uncommitted buffers up to the full amount of RAM onboard could be lost in such a scenario.

This is why servers will use a battery back up unit (BBU) on their hosts to retain uncommitted buffer for up to 72 hours.

 

[hclarkjr]

i am just waiting for western digital to release a 32MB cache drive then i will buy one and see for myself if there is difference. anybody know when WD will be releasing one?

 

[SickBeast]

Originally posted by: hclarkjr
i am just waiting for western digital to release a 32MB cache drive then i will buy one and see for myself if there is difference. anybody know when WD will be releasing one?

It's possible (but unlikely) on their 1tb drive in the near future, but really IMO it won't happen until their next generation in a year or so. The 320gb platters just came out and they're using 16mb, so I figure that's their standard for now.