SATA RAID 5 Performance

Hi all,
I'm in the process of researching a fast disk array for our new database
server.
I've been looking at SATA RAID 5. I found a review on Tom's Hardware:
http://www20.tomshardware.com/storage/20040831/sata-raid-controller-18.html
A 12 Disk RAID 5 array is only able to handle 6MB/S?! Is that number
correct... I belive they're using IOMeter.
Assuming I have 6 - 12 fast disks, what type of performance should I expect
from a RAID 5 array? Are there any RAID vendors I should look at in
particular?
Thanks.
--
Lucas Tam (REMOVEnntp@.rogers.com)
Please delete "REMOVE" from the e-mail address when replying.
http://members.ebay.com/aboutme/coolspot18/Lucas Tam wrote:
> Hi all,
> I'm in the process of researching a fast disk array for our new
> database server.
> I've been looking at SATA RAID 5. I found a review on Tom's Hardware:
>
http://www20.tomshardware.com/storage/20040831/sata-raid-controller-18.html
> A 12 Disk RAID 5 array is only able to handle 6MB/S?! Is that number
> correct... I belive they're using IOMeter.
> Assuming I have 6 - 12 fast disks, what type of performance should I
> expect from a RAID 5 array? Are there any RAID vendors I should look
> at in particular?
> Thanks.
RAID 5 has the worst write performance of all RAID options. I don't know
what figures you read or how they compare to other ATA or SATA
implementations, but you should know that if your databases are highly
transactional, then a RAID 5 solution may not be the best choice. You
may want to purchase a RAID1+0 solution. Even so, you'll likely want
your OS, Log files, and tempdb on mirrored drives because of their
increased write performance.
In my experience most RAID 5 arrays have far less than 12 disks. Most I
have seen use 5 per array.
David G.|||RAID5 certainly isn't designed to perform write operations as fast as
RAID1+0, but then again writes aren't written transactionally to disk on
data volumes (lazy writes) which often mitigates this significantly,
assuming there is a relatively large amount of memory available. RAID5 is a
poor choice for Log files, but not always a bad choice for Data files. Sure,
if you can throw half of your disks at mirroring, RAID1+0 is the way to go,
but RAID5 often cuts the mustard for many small to mid range transaction
processing systems.
Regards,
Greg Linwood
SQL Server MVP
"David G." <david_nospam@.nospam.com> wrote in message
news:OK0WIS6jEHA.3724@.TK2MSFTNGP11.phx.gbl...
> Lucas Tam wrote:
>> Hi all,
>> I'm in the process of researching a fast disk array for our new
>> database server.
>> I've been looking at SATA RAID 5. I found a review on Tom's Hardware:
>>
> http://www20.tomshardware.com/storage/20040831/sata-raid-controller-18.html
>> A 12 Disk RAID 5 array is only able to handle 6MB/S?! Is that number
>> correct... I belive they're using IOMeter.
>> Assuming I have 6 - 12 fast disks, what type of performance should I
>> expect from a RAID 5 array? Are there any RAID vendors I should look
>> at in particular?
>> Thanks.
> RAID 5 has the worst write performance of all RAID options. I don't know
> what figures you read or how they compare to other ATA or SATA
> implementations, but you should know that if your databases are highly
> transactional, then a RAID 5 solution may not be the best choice. You
> may want to purchase a RAID1+0 solution. Even so, you'll likely want
> your OS, Log files, and tempdb on mirrored drives because of their
> increased write performance.
> In my experience most RAID 5 arrays have far less than 12 disks. Most I
> have seen use 5 per array.
>
> --
> David G.
>|||See ftp://ftp.research.microsoft.com/pub/tr/tr-2003-70.pdf for some detailed
SATA disk test results.
GertD@.SQLDev.Net
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"Greg Linwood" <g_linwoodQhotmail.com> wrote in message
news:eLYskcBkEHA.704@.TK2MSFTNGP12.phx.gbl...
> RAID5 certainly isn't designed to perform write operations as fast as
> RAID1+0, but then again writes aren't written transactionally to disk on
> data volumes (lazy writes) which often mitigates this significantly,
> assuming there is a relatively large amount of memory available. RAID5 is
> a poor choice for Log files, but not always a bad choice for Data files.
> Sure, if you can throw half of your disks at mirroring, RAID1+0 is the way
> to go, but RAID5 often cuts the mustard for many small to mid range
> transaction processing systems.
> Regards,
> Greg Linwood
> SQL Server MVP
> "David G." <david_nospam@.nospam.com> wrote in message
> news:OK0WIS6jEHA.3724@.TK2MSFTNGP11.phx.gbl...
>> Lucas Tam wrote:
>> Hi all,
>> I'm in the process of researching a fast disk array for our new
>> database server.
>> I've been looking at SATA RAID 5. I found a review on Tom's Hardware:
>>
>> http://www20.tomshardware.com/storage/20040831/sata-raid-controller-18.html
>> A 12 Disk RAID 5 array is only able to handle 6MB/S?! Is that number
>> correct... I belive they're using IOMeter.
>> Assuming I have 6 - 12 fast disks, what type of performance should I
>> expect from a RAID 5 array? Are there any RAID vendors I should look
>> at in particular?
>> Thanks.
>> RAID 5 has the worst write performance of all RAID options. I don't know
>> what figures you read or how they compare to other ATA or SATA
>> implementations, but you should know that if your databases are highly
>> transactional, then a RAID 5 solution may not be the best choice. You
>> may want to purchase a RAID1+0 solution. Even so, you'll likely want
>> your OS, Log files, and tempdb on mirrored drives because of their
>> increased write performance.
>> In my experience most RAID 5 arrays have far less than 12 disks. Most I
>> have seen use 5 per array.
>>
>> --
>> David G.
>