use of SSD Raid-0 for RAW files ? (small reads)
Hi
When checking if using a SSD raid-0 to store my RAW files on, I did some tests:
I logged the read/writes while opening a RAW file on my SSD. This file was read in 32KB chunks, probably using a memory mapped file.
(one read command : "Offset: 884.736, Length: 32.768, I/O Flags: Non-cached, Paging I/O, Synchronous Paging I/O, Priority: Normal")
I got an "elapsed time" speed of about 170MB/s or about 0.2 sec/file while the CPU wasn't using 100%, more like 50-60%. This is more like a modern HDD not an SSD.
On my crucial M4 I then did some tests with ATTO QD=1 and it gave quite distinct results depending on block size :
32KB --> 264 MB/s
64KB --> 368 MB/s
256KB --> 445 MB/s
Using SSD's in RAID-0 will be probably not useful. A SSD that's good in 32KB read will be more useful.
BTW. While it's not possible to increase the chunk size with memory mapped files, it could be useful to start a different thread with a large block read (256KB a piece) to get the file in cache.
When checking if using a SSD raid-0 to store my RAW files on, I did some tests:
I logged the read/writes while opening a RAW file on my SSD. This file was read in 32KB chunks, probably using a memory mapped file.
(one read command : "Offset: 884.736, Length: 32.768, I/O Flags: Non-cached, Paging I/O, Synchronous Paging I/O, Priority: Normal")
I got an "elapsed time" speed of about 170MB/s or about 0.2 sec/file while the CPU wasn't using 100%, more like 50-60%. This is more like a modern HDD not an SSD.
On my crucial M4 I then did some tests with ATTO QD=1 and it gave quite distinct results depending on block size :
32KB --> 264 MB/s
64KB --> 368 MB/s
256KB --> 445 MB/s
Using SSD's in RAID-0 will be probably not useful. A SSD that's good in 32KB read will be more useful.
BTW. While it's not possible to increase the chunk size with memory mapped files, it could be useful to start a different thread with a large block read (256KB a piece) to get the file in cache.
0
-
Hi
I reran the tests with the RAW-directory on a recent -fast- HDD and got almost the same speeds. So even using a SSD for RAW files doesn't help much (I think 10% or so.).
I also noticed that it would be rather easy to improve the response, just read afew RAW files ahead and keep those a little longer in memory.
I did see that my computer had still plenty memory available, but no read ahead was taking place.0
Post is closed for comments.
Comments
1 comment