EMC RAID-5
Hi, Gurus We are using currently HP-UX 11.0, V 7200 and 64 bit O/S. We are using IDS 7.31 FC2. We have over 160 GB database. We have 4 physical CPUs and 3 CPUs assigned to informix. We are planning to migrate the data to EMC CLARiiON System 1 and RAID-5. Could someone please let me know pros and cons about it. I have tables with more than 35 GB size. I fragmented these tables into 3 fragments. I am new to this RAID-5 system. I think RAID-5 works in same concept of informix fragmentation. WE are going to have disks with 18 GB size. We are going to mirroring the disks. There will be 9 GB space available in each disc. How can I allocate the spaces. I confused here because of RAID-5. Can I create a single space for that table and assign 5 discs with 23 chunks, RAID-5 is going to create 5 threads to query. Am I correct? or Can I make it 5 fragments, I mean into 5 db spaces Please advice me ASAP. Thanks in advance.
Rao_Yalamanchili@apsnet.com wrote: > > Hi, Gurus Hi Rao, I got your email and have elected to respond here on the newgroup. > We are using currently HP-UX 11.0, V 7200 and 64 bit O/S. We are using IDS > 7.31 FC2. > We have over 160 GB database. We have 4 physical CPUs and 3 CPUs assigned > to informix. > > We are planning to migrate the data to EMC CLARiiON System 1 and RAID-5. AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA! NO RAID5 NO RAID5 NO RAID5 NO RAID5 NO RAID5 NO RAID5 NO RAID5 > Could someone please let me know pros and cons about it. > > I have tables with more than 35 GB size. I fragmented these tables into 3 > fragments. OK. > I am new to this RAID-5 system. I think RAID-5 works in same concept of > informix fragmentation. WE are going to have disks with 18 GB size. We NO! It is different. RAID5 and any striping scheme (RAID0, RAID3, RAID4, or RAID10) will give you some of the load balancing advantages of fragmentation but not the parallelism that fragmentation along with PDQ can give you and not the fragment elimination advantage either. are > going to mirroring the disks. There will be 9 GB space available in each > disc. WAIT! You are going to make RAID5 sets on the Clariions and then use Informix mirroring to mirror two RAID5 chunks? NO NO NO NO NO NO NO NO NO RAID5 give 1/2 the write performance of RAID0 (striping alone) and RAID10 will give a slight write performance increase over RAID0 so RAID5 is less than 1/2 the write performance of RAID10. In addition DG/EMC Clariions have an excellent RAID10 implementation which will outperform Informix mirror by a noticable margin and you will not have to waste the parity drives. In your case using RAID10 instead of RAID5 + mirror (ie RAID1) (what is that RAID51?) will actually cost you less or give you more storage for the same number of drives! In addition, there is a PROBLEM with using Clariion RAID5 with Informix. Though DG/EMC deny it (I have seen it happen for years though) if there is a RAID5 error, ie a lost drive, Informix will receive I/O errors for several seconds when the parity data reconstruction first kicks in and will mark your chunks offline even though the RAID5 is correcting the problem and returning good data. This does not happen with Clariion RAID10 when a drive fails! Use Clariion RAID10 and no Informix mirrors! > How can I allocate the spaces. I confused here because of RAID-5. > Can I create a single space for that table and assign 5 discs with 23 > chunks, RAID-5 is going to create 5 threads to query. > Am I correct? No! Informix will know nothing about the stripe and will assign a single I/O thread to the job! > or Can I make it 5 fragments, I mean into 5 db spaces If you want to take advantage of parallel searching you MUST use Informix fragmentation and fragment the table across multiple dbspaces, yes. > Please advice me ASAP. My advice? NO RAID5 NO RAID5 NO RAID5 NO RAID5 NO RAID5 NO RAID5 NO RAID5 NO RAID5 NO RAID5 NO RAID5 NO RAID5 NO RAID5 NO RAID5 NO RAID5 NO RAID5 NO RAID5 NO RAID5 NO RAID5 NO RAID5 NO RAID5 NO RAID5 NO RAID5 NO RAID5 NO RAID5 NO RAID5 NO RAID5 NO RAID5 NO RAID5 NO RAID5 NO RAID5 NO RAID5 NO RAID5 NO RAID5 NO RAID5 NO RAID5 For details on why, search the IIUG Archives of this newsgroup for my recent posts on the subject. Also Obnoxio the Clown has oined the party and made some good points. Art S. Kagel