Last year, Hewlett-Packard discontinued the servers and storage systems with SCSI drives, and began producing devices with SAS drives and SATA form factor 2.5 ...
Let's look at all the features of these drives.
There are specific differences in the following disks:.
a. Form Factor: 2.5 ...
2. Interface speed:.
3Gbit/sec or 1,5 Gbit/sec3. Number of ports in a disk controller, 1 or 2.
Form Factor.
So, what drives are currently most in demand and what price ratio \\ volume \\ performance?.
Format discs 2.5 ...
LFF drives are used in. servers. : HP Proliant DL160G5, DL165G5, DL180G5, DL185G5, DL320G5p, DL320s, ML150G5, ML310G5, ML350G5 and storage systems: HP StorageWorks 1200r, MSA 60, MSA 2000, as well as in the line Storage Server.
SFF drives are used in all servers Series BL, all servers, 3xx, 5xx, 7xx series storage systems in the HP StorageWorks 1200r, MSA 50, MSA 70, as well as in the line Storage Server.
Now it is clear that decisions on the SFF drives to be used in servers, mid -and high- level, as well as in compact storage systems and solutions to the LFF drives are suitable for entry-level servers and storage systems, which need to store large amounts of data. Installing the drive LFF in an entry-level server, over the same is justified because of the low cost of disk.
The cost of the most common drive SAS: Drives 72Gb SAS SFF SP 15K offered at $ 495, while the disc 72Gb SAS LFF SP 15K offered at $ 240. As we see the same characteristics of wheels, but different in form factor, differ in value at times. I want to emphasize that the maximum amount at this time for SFF is 146Gb, but for the LFF 1Tb drives.
Also, it is important to note the low power drive form factor 2.5 ... For example, consider a typical file system:.
The file system on the 1Tb Raid 5 with:.
8 * 146Gb 10K SAS SFF maximum power consumption of the system 8 * 9W = 72W.
4 * 300Gb 15K SAS LFF maximum power consumption of the system 4 * 18,5 W = 74W.
15 * 72GB 15K SAS SFF maximum power consumption of the system 15 * 9,5 W = 142,5 W.
Saving energy in the SFF drives in the construction of large raids is not observed, m. to. this increases the number of disks. SFF drives in terms of energy savings are beneficial when used as system disks that do not require large volumes, and requires 2.4 drives in raid.
In all other cases, a careful calculation of electricity from light to reduce power consumption when idle disk. On average, the SFF drive same volume and speed of rotation of the disk LFF consumes 40 % less energy. From this it is easy to see that if the number of disks in a raid in the transition form factor with the LFF to SFF form factor is doubled, then this transition will increase the power consumption of the entire file system.
speed interface.
It is now widely used by the two interfaces - SAS and SATA. SAS interface has a maximum throughput of 3Gb / s, while SATA controllers do not have long to maintain this ability. Previously, all HP servers have the SATA controller with a capacity of 1,5 Gb / s, although the discs have long been used by SATA-II with a capacity of 3Gb / s. HP announced that when you update the controller BIOS, most controllers will be able to support 3Gb / s.
The number of ports, the disk controller.
Many have already met with the notation of the SP and DP. SP - an abbreviation for single port ( port 1 ), DP - is short for dual port ( 2 ports). Drives with DP have 2 ports for data transfer, they are more versatile solution than drives SP. At the moment the function DP is realized only in the storage system StorageWorks MSA 70, if it uses a controller HP StorageWorks Dual Domain I / O Module Option (AG779A), and all the disks in the storage system DP. In this case, it will be possible to use technology Dual Domain, which will increase the performance of an array of up to 30%.
Conclusion:.
In general, the usefulness of the transition to a new form factor disks is difficult to assess. T. to. this transition has a number of pros and cons. In conclusion, we list the main advantages and disadvantages of each of the factors:.
pros.
A small disk mass, can significantly reduce the weight of large storage systems.
Low power consumption Raid- Arrays of small volume.
cons.
High energy Raid- array of large volume, due to the small maximum size have to install a large number of disks.
The high cost of disks, as well as the high cost solutions, which use data discs.
The low maximum. For SAS 146Gb, SATA 120GB to.
pros:.
Large maximum amount, up to 1TB SAS and SATA.
Low-cost drives, as well as solutions in which these drives are used.
Higher access time when comparing two similar drives 2.5 ...
cons:.
The large mass of the disk, the total mass of a large storage system will be great.
High power consumption of each individual disk.