版主
版主

【微博用户提问分享】SAS2.0和SATA3.0的技术对比

转到解答

来自微博用户 @LZ慢慢Beta  的提问:

“#存储#那位大神能给说说SAS 2.0 和 SATA 3.0的技术对比,我想了解两种接口硬盘在性能和可靠性上的差距。看了一下两种的接口速率差不多都是6Gb/秒。 如果自制个NAS,用来做exsi存储,不知道用sata靠得住靠不住?不用着关键性业务。@EMC易安信中国技术社区”

SASvsSATA.jpg

EMC易安信中文技术社区新浪微博
http://www.weibo.com/emcsupport


请大家分享点经验和信息高兴表情

标签 (1)
标记 (2)
0 项奖励
1 个已接受解答

已接受的解答
FDU1
1 Nickel

Re: 【微博用户提问分享】SAS2.0和SATA3.0的技术对比

转到解答

参考http://en.wikipedia.org/wiki/Serial_attached_SCSI#Comparison_with_SATA 它们的技术区别如下:

 

  • Systems identify SATA devices by their port number connected to the host bus adapter, while SAS devices are uniquely identified by their World Wide Name (WWN).
  • SAS protocol provides for multiple initiators in a SAS domain, while SATA has no analogous provision.
  • Most SAS drives provide tagged command queuing, while most newer SATA drives provide native command queuing, each of which has its pros and cons.
  • SATA uses the ATA command set; SAS uses the SCSI command set. Basic ATA has commands only for direct-access storage. However SCSI commands may be tunneled through ATA for devices such as CD/DVD drives.
  • SAS hardware allows multipath I/O to devices while SATA (prior to SATA 3Gb/s) does not. Per specification, SATA 3Gb/s makes use of port multipliers to achieve port expansion. Some port multiplier manufacturers have implemented multipath I/O using port multiplier hardware.
  • SATA is marketed as a general-purpose successor to parallel ATA and has become common in the consumer market, whereas the more-expensive SAS targets critical server applications.
  • SAS error-recovery and error-reporting use SCSI commands which have more functionality than the ATA SMART commands used by SATA drives.
  • SAS uses higher signaling voltages (800–1600 mV TX, 275–1600 mV RX) than SATA (400–600 mV TX, 325–600 mV RX). The higher voltage offers (among other features) the ability to use SAS in server backplanes.
  • Because of its higher signaling voltages, SAS can use cables up to 10 m (33 ft) long, SATA has a cable-length limit of 1 m (3 ft) or 2 m (6.6 ft) for eSATA.

另外在物理规格上,SAS最重要的是支持dual-ported,一块SAS盘可以连接两个SAS HBA实现更高的可用性:

dual_port_cable.jpg

还有一点就是,目前SATA和SAS的平均无故障时间 (MTBF)已经很接近了,但误码率(BER) SATA要比SAS高10倍(10^15分之一 vs 10^16分之一),从可靠度来讲SAS比SATA高许多,因此通常建议由SATA或NL-SAS组成的RAID group尽可能采用RAID 6而不要使用RAID 5。

0 项奖励
4 条回复4
Yanhong1
4 Germanium

Re: 【微博用户提问分享】SAS2.0和SATA3.0的技术对比

转到解答

我先来抛个砖,

http://zh.wikipedia.org/wiki/SATA 这个里面Sata的讲的比较全

http://zh.wikipedia.org/wiki/%E4%B8%B2%E5%88%97SCSI 这里面SAS讲了一些,这里还有一篇文章也挺不错的。http://stor-age.zdnet.com.cn/stor-age/2010/0225/1640259.shtml

0 项奖励
zhouzengchao
4 Germanium

Re: 【微博用户提问分享】SAS2.0和SATA3.0的技术对比

转到解答

个人觉得这是一个宽泛而复杂的问题,我能想到的大致如下:

(1)性能:我能想到的只有转速了,SATA没有提供如同SAS盘那样快的转速,这相信是性能上最大的差异。不过也有另一种说法是,ATA的设计就是在低成本下尽量实现高性能,而SCSI本身就是面向高性能设计的,即便是相同转速的SATA和SAS盘,性能也会有很大差距。个人还没研究到那份上,还需要山中大侠指教了。

(2)可靠性:可靠性取决于磁头、盘片已经生产工艺,而和接口无关。所以,SATA和SAS在可靠性上的差异变得越来越小。不过个人觉得,SAS和SATA使用的command-set不同,所以在错误处理能力上一定会有差距。

0 项奖励
FDU1
1 Nickel

Re: 【微博用户提问分享】SAS2.0和SATA3.0的技术对比

转到解答

参考http://en.wikipedia.org/wiki/Serial_attached_SCSI#Comparison_with_SATA 它们的技术区别如下:

 

  • Systems identify SATA devices by their port number connected to the host bus adapter, while SAS devices are uniquely identified by their World Wide Name (WWN).
  • SAS protocol provides for multiple initiators in a SAS domain, while SATA has no analogous provision.
  • Most SAS drives provide tagged command queuing, while most newer SATA drives provide native command queuing, each of which has its pros and cons.
  • SATA uses the ATA command set; SAS uses the SCSI command set. Basic ATA has commands only for direct-access storage. However SCSI commands may be tunneled through ATA for devices such as CD/DVD drives.
  • SAS hardware allows multipath I/O to devices while SATA (prior to SATA 3Gb/s) does not. Per specification, SATA 3Gb/s makes use of port multipliers to achieve port expansion. Some port multiplier manufacturers have implemented multipath I/O using port multiplier hardware.
  • SATA is marketed as a general-purpose successor to parallel ATA and has become common in the consumer market, whereas the more-expensive SAS targets critical server applications.
  • SAS error-recovery and error-reporting use SCSI commands which have more functionality than the ATA SMART commands used by SATA drives.
  • SAS uses higher signaling voltages (800–1600 mV TX, 275–1600 mV RX) than SATA (400–600 mV TX, 325–600 mV RX). The higher voltage offers (among other features) the ability to use SAS in server backplanes.
  • Because of its higher signaling voltages, SAS can use cables up to 10 m (33 ft) long, SATA has a cable-length limit of 1 m (3 ft) or 2 m (6.6 ft) for eSATA.

另外在物理规格上,SAS最重要的是支持dual-ported,一块SAS盘可以连接两个SAS HBA实现更高的可用性:

dual_port_cable.jpg

还有一点就是,目前SATA和SAS的平均无故障时间 (MTBF)已经很接近了,但误码率(BER) SATA要比SAS高10倍(10^15分之一 vs 10^16分之一),从可靠度来讲SAS比SATA高许多,因此通常建议由SATA或NL-SAS组成的RAID group尽可能采用RAID 6而不要使用RAID 5。

0 项奖励
Highlighted
Celia_Lee
2 Iron

Re: 【微博用户提问分享】SAS2.0和SATA3.0的技术对比

转到解答

SAS只是个磁盘访问的传送协议,而其会不会影响你的性能, 取决于你的性能瓶颈是不是在磁盘上. 存储的性能分析是个较复杂的课题, 要具体情况具体分析. 存储的性能和存储区域网络架构,主机多链路管理软件,存储的控制器处理性能, 缓存,RAID类型等等非常多的因素都有密切相关. 甚至于一个主机的操作系统的补丁的版本也能影响到存储传输的40%应用性能.

而专用的NAS存储所提供的也不仅仅是性能的提升,更重要的是单点故障和数据的高可用性,可靠性和安全性.

SATA和SAS本身除了转速的影响以外, SAS使用SCSI的指令集, 更适用于并发的数据读写,所以在多磁盘并发访问的时候更有性能优势. 而信道的传送频率在6.0G的时候,任意单盘都无法占满整个带宽,

而SAS本身单个端口实际由4个LANE的信道组成,每个信道都有6G的带宽. 所以除非使用Flash Drive, 信道的带宽本身在大多数情况下, 不会成为性能的瓶颈. 所以在很多性能调优的例子中,都尽量减少后端parity的计算, 增加并发读写的物理磁盘数量, 最大化所有链路的负载均衡来提升存储后端的性能.