SATA 7.2K HD Suitable for File Server

file-sharinghard driveraid

Just discussing a new Server with a client and they are insisting on using two 3Tb 7.2K SATA Driver in RAID 1. I wanted to get them 5 15K SAS Drives in RAID 5.

Can anyone tell me what the true speed difference will be between these two setups? Will they actually notice a huge improvement with 15K SAS drives over the 7.2K SATA's?

It will be a File Server holding around 1Tb of data for about 200 users across the UK.

Best Answer

  1. They are not so error-prone. A 3-raid1 is a very redundant configuration, it practically means that all of the disks should be gone to a data loss. On the 5 disk-raid5 were already 2 enough to loss your data.
  2. It is faster. For reading, you can execute 4 parallel read task in a five-disk raid5. For write, you have to update 4 blocks to change a single one. But writing speed is not so important: first, because writing can happen delayed, from the write block cache, and second, because most of such systems are writing much fewer as reading. Next to these structural things there is the around 2-3 times greater speed of the SAS disks.
  3. It is much more efficient. The cost of the extrem big redundancy of the first setup was, that you had to use 3 disks instead of 1. 2 of the disks were only practically dead copies. In the new system, there is only 20% redundancy.

I must also mention:

  1. Some of the professional system administrators here are thinking, that using raid5 is actually not okay, because there is a too big chance of a simultaneous disk collapse (because the disks are coming probably from the same manufacturer, same serie, so there is a bigger chance of the same structural problem.) My opinion is not the same: I experienced a such stiuation 2 times in 15 years, so you need to have only good backups.
  2. And yes: raid is not backup! Raid doesn't protect against accidental deletion, against attacks, against software failures and such! Only backup can protect against them. I suggest to think a lot more on your backup solution, as on your raid solution - on my experience, the first is much more important.
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