Storage Performance

Storage has changed dramatically over the last three years driven by SSD developments. Most of the key components necessary for a powerful storage system are available and the cost is highly favorable for direct placement of data files. Some additional infrastructure elements could greatly enhance the flexibility of storage systems with SSDs. There is still some discussion on whether SSD should interface directly to PCI-E or continue using the SAS/SATA interfaces originally designed for hard disks….(read more)

Summary: Some of the discussion on PCI-E versus SATA/SAS interface for the NAND/Flash controller incorrectly focuses on the bandwidth of a single 6Gbps lane versus 4 or 8 lanes on PCI-E.

…Some Dell servers today support PCI-E to SSDs in the 2.5in HDD form factor (SFF), but I am not sure if this is Express Bay.

…If this were issued at low queue depth (2?), then the storage system would not only generate high IO bandwidth and still be perceptually responsive to other requests for small block IO.

…The only other place 4 comes up is with the net bandwidth of 2 x4 SAS 6Gbps or 1 x4 12Gbps SAS, which is 4.4GB/s, but I use 4GB/s for brevity.

…Because the database to be migrated already had a single 3TB file, there was no way we could build 8 x 4 disk RAID groups on each MD3200, to get near 100MB/s per disk, for 2.8GB/s per MD3200.
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