Any risks of using RAID 0 with Tempdb? | SQL Server Performance Forums

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Any risks of using RAID 0 with Tempdb?

We have traditionally used RAID 1 for Tempdb and T-logs, RAID 10 for databases and RAID 10 for data and log backups. Recently a consulting company recommended using RAID 0 for Tempdb. I’ve also read about using RAID 0 for tempdb on this site, but I’m still unclear as to the risks for tempdb, if any. What are the risks of keeping Tempdb on RAID 1, especially knowing there is no redundancy? Also, is RAID 10 overkill for Logs? Thanks, Dave
I haven’t seen any risks (on few systems at my end) yet and the reason is simply that TempDB is rebuilt each time the server is started. This means that there are no real recovery issues with TempDB. However, there is the problem that such data loss will require the system to be restarted. In a 24×7 E-Commerce environment, this may not be an option. _________
Satya SKJ
Moderator
SQL-Server-Performance.Com
Satya, Thanks for the comments. My assumption is that if the system is high-availability then RAID 1 should not be chosen. Please correct me if I am wrong, but if for example 5 disks are being used in RAID 1 for tempdb and one dies, tempdb dies. The down-time would be the amount of time it takes to replace the disk or reconfigure RAID 1 to use 4 disks instead of 5. Conversely with RAID 0 if a disk dies, the system may slow slightly, but it won’t be dead until a second disk dies. Dave
RAID 10 is fine for Transaction logs as this gives the best perfomance and reliability. Gaurav
Moderator
Man thrives, oddly enough, only in the presence of a challenging environment- L. Ron Hubbard
Wait a minute, RAID 1 will intrduce redundancy in the system and you’ll have one mirror disk for each disk in the array. Whereas RAID 0 will just stipr the data across disks. So the chances of database going down in RAID 0 are more. Gaurav
Moderator
Man thrives, oddly enough, only in the presence of a challenging environment- L. Ron Hubbard
Dave Could you please clarify whether you want to put Tempdb on RAID 1 or RAID 0, your thread contradicts with heading and query. _________
Satya SKJ
Moderator
SQL-Server-Performance.Com
With TempDB, read/write performance rather than fault tolerance is the primary concern. In any case, any recovery of the server after an outage will recreate the tempdb database in line with default behaviour of SQL Server. The decision to place the tempdb on a RAID 0 disk architecture should actually depend on the kind and intensity of read/write activity on your server. I would outrightly say that there is no ‘risk’ associated with placing it on RAID 0. Nathan H.O.
Moderator
SQL-Server-Performance.com
I would have to agree with satya. The risk involved with RAID 0 is that if one disk crashes in your RAID 0 array you need to recover the array and then restart the system. If you can live with that then RAID 0 is fine. If you can’t choose RAID 1 or RAID 10. /Argyle
Sorry guys I mispoke previously. I meant to say that RAID 0 should not be chosen for tempdb since it offers no redundancy. My bad.
Yes risks are involved in RAID 0 and not suitable for 24/7 systems, but as of now for 2 services no issues (and they’nt 24/7 ones). _________
Satya SKJ
Moderator
SQL-Server-Performance.Com
Thanks for all of your input. I believe I am leaning towards RAID 1 or 10, depending upon the application. With all the advancement in read-ahead cash, disk rotational speed and bus speed I’m guessing the differnce in RAID performance is not nearly as noticeable as in times past. Nathan, I’m not sure I can agree RAID 0 offers no risk. What about the risk of down time? If a disk dies in the midst of batch processing you need to down the server and replace the disk or down the server and change the stripe set to include less disks. Once this is done the batch jobs need to be restarted from prior to the point of disk failure. Developers and/or DBAs will also need to spend time verifying at what point in the batch process data was committed to the databases. With a small batch window this could present large problems. I’m also guessing the same arguement would hold true with critical online processing. Admittedly I am not as familiar with server clustering so perhaps there is a way to minimize the risk of down time from RAID 0 with a clustering approach. Thanks again, Dave
BTW what kind of application is that using SQL db, is it OLTP or normal?
The type of applications vary per server. Several servers run OLTP, DSS and batch with Powerbuilder, VB, HTML, and SQL. Other servers are primarily web scripting and SQL and a few have packaged applications. Dave
THen go for RAID 1 or 10. _________
Satya SKJ
Moderator
SQL-Server-Performance.Com
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