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Are RAID Controllers the Next Data Center Bottleneck?
storagedude writes "This article suggests that most RAID controllers are completely unprepared for solid state drives and parallel file systems, all but guaranteeing another I/O bottleneck in data centers and another round of fixes and upgrades. What's more, some unnamed RAID vendors don't seem to even want to hear about the problem. Quoting: 'Common wisdom has held until now that I/O is random. This may have been true for many applications and file system allocation methodologies in the recent past, but with new file system allocation methods, pNFS and most importantly SSDs, the world as we know it is changing fast. RAID storage vendors who say that IOPS are all that matters for their controllers will be wrong within the next 18 months, if they aren't already.'"
FTA Since a disk sector is 512 bytes, requests would translate to 26.9 MB/sec if 55,000 IOPS were done with this size. On the other end of testing for small block random is 8192 byte I/O requests, which are likely the largest request sizes that are considered small block I/O, which translates into 429.7 MB/sec with 55,000 requests
I'm not going to believe an article that assumes that because you can do 55K IOPS for 512Byte reads, you can do the same number of IOPS for 8K reads which are 16X larger and then just extrapolate from there. Especially since most SSD's (at least SATA ones) right now top out around 200MB/s and the SATA interface tops out at 300MB/s. Besides there are already real world articles out there where guys with simple RAID0 SSD's are getting 500-600 MB with 3-4 drives using Motherboard RAID much less dedicated harware RAID.