Performance impact on downgrade from 15k SAS to 7.2k SAS/SATA


I am trying to expand the capacity of our exchange server, right now it is running on Raid 1

Fujitsu MBA3147RC 147GB 15000 RPM 16MB Cache Serial Attached SCSI (SAS) 3.5" Internal Hard Drive -Bare Drive

I would like to change it to either

Seagate Constellation ES 1 TB 7200RPM 6 Gb/s SAS 64MB Cache 3.5 Inch Internal Bare Drive (ST1000NM0001)


WD Red 1 TB NAS Hard Drive: 3.5 Inch, SATA III, 64 MB Cache - WD10EFRX

I am running these on old hardware so it's only capable of 3GB/s, which is why I am not getting high end SAS drives.  

Capacity wise it is more than what I need, I am just wondering what the performance impact will be. These drives are slower but I am wondering if it will be more than enough to handle an exchange server of 50~ users. Any advice or alternative suggestion would be greatly appreciated, thanks.
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PowerEdgeTechConnect With a Mentor IT ConsultantCommented:
There should be negligible performance loss at 10Mb/s ... just keep in mind that it is not the maximum throughput that is most important - the higher latency and seek time of the slower rotation will affect the number of transactions per second the disks can handle, too.  50 isn't necessarily a lot of users, but it depends on how it's used - and if you have more than one server serving those users, then I definitely can't see how the slower speed will have much of an effect.
PowerEdgeTechIT ConsultantCommented:
What model server and RAID controller are we working with here?  MOST controllers will not allow you to mix SAS and SATA in an array, so you would be doing a full backup/restore to move to SATA drives ... just as a head's up.

If you have the available slots, you might consider adding drives and converting to a RAID 5 or 6 (most controllers support this on the fly) ... that would increase your capacity, while keeping you in SAS drives - and preventing the need for a full backup/restore.  Sure, there is a performance hit with RAID 5 and 6, but it won't be as severe as going to 7200RPM SATA drives.
WangstaaAuthor Commented:
for the exchange servers I am planning, they are using PowerEdge 1950 III, so only 2 slots and Perc 5/6i cards. I would not be mixing SATA/SAS cards, I would be replacing them completely.

The exchange servers are not super busy, idling at 10mb/s most of the time, my assumption is that there would be no performance impact since the existing hard drives are not being stressed at all.
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PowerEdgeTechIT ConsultantCommented:
If you plan to do a complete backup/restore, then there shouldn't be an issue - they'll take both types of drives.

I'd get the Seagate drives though over the WD ... they are more likely to work on the PERC's without issue than the WD Red.
WangstaaAuthor Commented:
Can you confirm my assumption in terms of close to zero performance impact because of the lack of activity?
WangstaaAuthor Commented:
Yup, I have 2 exchange server cluster. So this would be good, thanks.
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